Network Working Group M. Vaško, Ed. Internet-Draft CESNET Updates: 7950 (if approved) P. Andersson Intended status: Standards Track Ionio Systems Expires: 25 April 2027 R. Wilton Cisco Systems, Inc. 22 October 2026 YANG Schema Comparison draft-ietf-netmod-yang-schema-comparison-10 Abstract This document specifies an algorithm with two input variants for comparing revisions of a YANG schema to determine the scope of changes and produce a list of the changes between the revisions. The output of the algorithm can be used to help select an appropriate YANG semantic version number for a new YANG Module revision. It also specifies a YANG module for YANG-structured output of these algorithms, that can be easily consumed in a machine-readable way. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 25 April 2027. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights Vaško, et al. Expires 25 April 2027 [Page 1] Internet-Draft YANG Schema Comparison October 2026 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3 3. Schema representations . . . . . . . . . . . . . . . . . . . 4 3.1. Locally resolved module (single module) . . . . . . . . . 4 3.1.1. Deviation . . . . . . . . . . . . . . . . . . . . . . 4 3.1.2. Refine . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.3. Augment . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Fully resolved schema (set of modules) . . . . . . . . . 5 3.3. Choosing a schema representation . . . . . . . . . . . . 7 3.3.1. Examples . . . . . . . . . . . . . . . . . . . . . . 8 4. Comparison algorithm . . . . . . . . . . . . . . . . . . . . 8 4.1. Module identification . . . . . . . . . . . . . . . . . . 9 4.2. Change conformance . . . . . . . . . . . . . . . . . . . 9 4.2.1. Deviations, Refines, and Augments . . . . . . . . . . 9 4.2.2. Conformance extensions . . . . . . . . . . . . . . . 10 4.3. Algorithm variants support . . . . . . . . . . . . . . . 11 5. Schema Comparison YANG Module . . . . . . . . . . . . . . . . 11 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 8.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 15 8.2. The "YANG Module Names" Registry . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . 16 9.2. Informative References . . . . . . . . . . . . . . . . . 18 Appendix A. Schema Comparison Algorithm Output YANG Module . . . 18 A.1. Tree diagram . . . . . . . . . . . . . . . . . . . . . . 49 Appendix B. Change Conformance Principles . . . . . . . . . . . 75 B.1. Editorial change . . . . . . . . . . . . . . . . . . . . 75 B.2. Backwards-compatible change . . . . . . . . . . . . . . . 76 B.3. Non-backwards-compatible change . . . . . . . . . . . . . 76 Appendix C. Comparison Examples . . . . . . . . . . . . . . . . 76 C.1. New Leaves Module . . . . . . . . . . . . . . . . . . . . 77 C.2. Relaxed Length Module . . . . . . . . . . . . . . . . . . 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 82 Vaško, et al. Expires 25 April 2027 [Page 2] Internet-Draft YANG Schema Comparison October 2026 1. Introduction This document defines a common algorithm for comparing two revisions of a YANG schema. As input, there can be two types of YANG schema representations: single locally resolved YANG modules or fully resolved set of YANG modules (on-the-wire schema). The algorithm output for each of these representations serves a different purpose. It can help YANG authors with assigning the correct semantic version of a module based on [I-D.ietf-netmod-yang-semver] or tools processing YANG instance data can use it to learn about the exact data changes, respectively. The algorithm operates in a straightforward way traversing all the statements and their substatements in both the old and new module representations collecting identified changes. These are then reported in a concise output with information about the overall backwards compatibility between the two modules. Exact output format is out of scope for this document but Appendix A includes an example of a YANG module whose YANG data can represent all the possible changes and so a complete output of this algorithm. Every change is classified as editorial, backwards-compatible, or non-backwards-compatible. This conformance is decided based on rules found in other documents, specifically [RFC7950], [I-D.ietf-netmod-yang-module-versioning], and [I-D.ietf-netmod-yang-semver]. For older YANG 1.0 modules, the rules in [RFC6020] apply instead. 2. Terminology and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This document makes use of the following terminology introduced in the YANG 1.1 Data Modeling Language [RFC7950]: * module * schema node * data node * data definition statement In addition, this document uses the following terminology: Vaško, et al. Expires 25 April 2027 [Page 3] Internet-Draft YANG Schema Comparison October 2026 * locally resolved module: A parsed YANG module with all its submodules and local references resolved. * fully resolved schema: A locally resolved module with all the imported references resolved as well and with non data definition statements removed. 3. Schema representations The YANG language defines several statements that act as syntactic abstraction and need to be processed before a YANG module can be used for handling YANG instance data. For example, a “uses” statement is replaced by all the substatements of a referenced “grouping” statement or a “typedef” statement can be linked to other “type” statements. The referenced statements can be local (defined in the same module, or included submodule) but also foreign (defined in another imported module). 3.1. Locally resolved module (single module) This representation of a YANG module includes all submodules of the main module but resolves only statements that reference other statements found in the same module. No references to imported modules (that are using an imported prefix) are resolved. For example, any changes of a referenced “typedef” or “grouping” defined in an imported module would not affect the locally resolved module and are out of scope for this representation. All the rules for classifying individual statement changes mentioned in Section 4.2 apply to this module representation. 3.1.1. Deviation Regardless of whether the “deviation” target node is local in the same module or in an imported module, it is never resolved and applied. Instead, the “deviation” statement with all its substatements is kept in the locally resolved module so that it can be considered in the schema comparison algorithm. 3.1.2. Refine The “refine” statement is processed differently based on whether the affected “grouping” is defined in an imported module or the local YANG module. In the former case, when the relevant grouping is imported, the “refine” is not resolved and kept in the module. And then examined in the comparison algorithm, similarly to the “deviation” statement. Vaško, et al. Expires 25 April 2027 [Page 4] Internet-Draft YANG Schema Comparison October 2026 However, all the “refine” statements targeting a local “grouping” are applied on the nodes of the grouping when the “uses” is resolved. After processing the “refine” statements with all its substatements, they are effectively removed from the locally resolved module to avoid reporting changes of any “refine” statements twice. 3.1.3. Augment All the “augment” statements are processed similarly to “refine” statements. Meaning that augments of imported groupings are not resolved and compared directly while augments of local groupings are applied and then removed from the module. 3.2. Fully resolved schema (set of modules) The fully resolved schema representation consists of one or more YANG modules. Each of these is fully resolved according to the rules of the YANG language meaning that every referenced statement, including to other imported modules, is resolved, unlike locally resolved modules. The result is one large tree with schema nodes of all the YANG modules. The comparison algorithm MAY then choose to compare top-level schema node subtrees belonging only to a single YANG module. Next, all the statements used only for syntactic abstraction that do not affect YANG instance data are removed. Note that the “description” or “units” statements are kept because they may influence the data. Also, “error-app-tag” and “error-message” statements remain in the fully resolved schema for applications to learn that the generated error information has changed. The steps taken when fully resolving a module include: * All submodules of a single module are merged to create one large YANG module. * "Import" statements are resolved by finding the referenced YANG modules and making their contents available. * "Uses" statements are replaced by the referenced "groupings" and the YANG nodes they define. Any “when” statement of the “uses” is moved down to all the direct descendant schema nodes of the “grouping”. * Types referencing any "typedef" statements are replaced with the actual type details. Vaško, et al. Expires 25 April 2027 [Page 5] Internet-Draft YANG Schema Comparison October 2026 * Augments are resolved by placing the included YANG nodes in their targets. Any “when” statement of the “augment” is moved down to all the direct descendant schema nodes of the “augment”. * "Deviation" and "refine" statements are applied by changing the appropriate schema nodes. * All the "if-feature" statements are evaluated based on the enabled "features" of implemented YANG modules and the disabled schema nodes are removed. * All the extension-instances have a matching “extension” defintion. After the resolution, the following statements are completely removed with their substatements: * organization * contact * reference * import * include * revision * typedef * grouping * augment * deviation * feature * if-feature * refine * extension Also, these schema nodes are removed but replaced with their schema node substatements: * choice Vaško, et al. Expires 25 April 2027 [Page 6] Internet-Draft YANG Schema Comparison October 2026 * case The term “schema” was chosen instead of “module” on purpose because when statements are imported from external modules, the resulting schema then includes statements from several YANG modules. But the fully resolved schema representation of a module always includes only the top-level schema node trees of that module. Only a subset of the module update rules in Section 4.2 apply for the fully resolved schema. Specifically, the rules for removed statements cannot be applied but other present statements are processed normally. How the concrete set of YANG modules of a fully resolved schema is described is out of scope of this document. But suitable existing structures include YANG data of “ietf-yang-library” from [RFC8525] or “ietf-yang-package-instance” in [I-D.ietf-netmod-yang-packages]. 3.3. Choosing a schema representation Selecting a suitable schema representation for the comparison algorithm depends on the desired purpose. But for a complete set of changes, both the representations should be compared and their output merged to get the combined output of the two comparisons. YANG module authors will primarily be interested in the locally resolved module representation. Using it for the comparison algorithm will yield all the changes that occurred in the specific YANG module only while ignoring any possible changes in imported modules. This information can then directly be used to decide the correct semantic version of the new revision of this module. The rules for selecting versions are defined in [I-D.ietf-netmod-yang-semver]. Any YANG-based application handling YANG instance data always uses the fully resolved schema representation. So, when running the schema comparison algorithm with the intent of learning the changes in the corresponding valid YANG instance data of the module, this representation should be used. With some additional information, the output of this comparison can then also be used to transform valid data of the old schema revision to data valid for the new schema revision. All these tools and applications are typically clients or servers of YANG-driven protocols, e.g. NETCONF, RESTCONF, or gRPC. Vaško, et al. Expires 25 April 2027 [Page 7] Internet-Draft YANG Schema Comparison October 2026 3.3.1. Examples To illustrate the different output of the comparison algorithm each schema representation can generate for the same YANG module changes, following are a few examples. When a “typedef” or “grouping” name changes, the algorithm for locally resolved module will detect the change and report it as non- backwards-compatible. This is useful especially when importing such a module to learn that any references to the original statements will no longer be valid. However, if using the fully resolved schema, this difference will not be detected at all since it does not affect YANG instance data corresponding to this module. Another specific use-case is when a module with “uses” that referenced an external “grouping” replaces that “uses” node directly with schema nodes in the “grouping” effectively resolving the “uses” similarly to a YANG module parser. Such a change is non-backwards- compatible based on the YANG 1.1 updating rules and reported that way when using a locally resolved module. But the fully resolved schemas will be completely the same before and after the change so the comparison algorithm will not generate any changes and report full compatibility of the old and the new modules with their instance data. 4. Comparison algorithm This algorithm is defined for individual locally resolved modules and fully resolved schemas. All the statements are compared with their content, recursively, in the old revision and the new revision of the module or schema. Depth-first search order for the statement traversal SHOULD be used. The non data definition statements are considered modified when their content is changed or any of their substatements are changed. If a statement is present in the old revision and missing in the new revision, it is considered removed. Conversely, if missing in the old revision but present in the new revision, it is considered added. Data definition statements are compared similarly except that a change in a descendant data definition statement is not considered a change of the parent data definition statement but a separate change instead. Only statements with any changes are reported and included in the comparison algorithm output. Vaško, et al. Expires 25 April 2027 [Page 8] Internet-Draft YANG Schema Comparison October 2026 4.1. Module identification When generating the comparison output of two modules, unique identification of these modules SHOULD be included. For both the old and the new revision of the base module, its name, revision, list of submodules, and a leaf-list of enabled features is included. For the fully resolved schema, the same information is also reported for all the imported YANG modules, recursively. This ensures that if any other output is produced with a different set of changes for two fully resolved schemas, their identification information must also differ. 4.2. Change conformance Every change is classified as editorial, backwards-compatible, or non-backwards-compatible. The classification is based on Section 11 of [RFC7950] which mentions most of the possible changes between two revisions of a YANG 1.1 module and Section 3.1 of [I-D.ietf-netmod-yang-module-versioning] adds more details about the exact conformance of statements with various "status" statement values. Finally, [I-D.ietf-netmod-yang-semver] defines what classifies as an editorial change. General non-normative explanation of change conformance classification can be found in Appendix B. 4.2.1. Deviations, Refines, and Augments All the statement change conformance follows the general rules above if these statements are present in the schema representation, see Section 3. But this clarification is added to make certain that the rules are interpreted correctly. Since “deviation” and “refine” statements are not among the allowed statements that can be changed when updating a module in Section 11 of [RFC7950], any non-editorial change of these statements or their substatements is treated as non-backwards-compatible. But since “augment” statements can only add schema nodes, these can be processed and compared normally. Vaško, et al. Expires 25 April 2027 [Page 9] Internet-Draft YANG Schema Comparison October 2026 So, for example, even if removing the “mandatory” statement is considered backwards-compatible, a new “deviation” removing the “mandatory” statement from its target node is considered a non- backwards-compatible change. Similarly a “refine” of the “description” of a node is classified as non-backward-compatible change. However, a change in the “description” of a “deviation” statement is treated as a standard “description” change because it describes the “deviation” statement itself and does not affect the deviation target node. 4.2.2. Conformance extensions There are cases when it may be impossible for tooling to accurately determine the conformance of a change but a default conformance is always assumed for every statement. The affected ambiguous statements with their default conformances are: * pattern - NBC * when - NBC * must - NBC * description - Editorial * reference - Editorial * presence - Editorial * extension instance - BC Normally, any modification of these statements is reported with the default change conformance. However, if the author of the new revision of a YANG module determines that the change of one of the aforementioned statements has a different conformance based on the compatibility rules for the specific statement, they can decide to use the special extension instances to signify this fact. These are: * ed-change-at SEMVER * bc-change-at SEMVER * nbc-change-at SEMVER They determine the conformance of the change of the marked statement to be editorial, backwards-compatible, or non-backwards-compatible, respectively. The argument is a semantic version of the YANG module revision that introduced the specific change and these extension Vaško, et al. Expires 25 April 2027 [Page 10] Internet-Draft YANG Schema Comparison October 2026 instances are sticky, meaning they remain in the module even in its later revisions. Also, a YANG statement can have multiple conformance extension statements. For example, when a pattern changes in multiple versions of a module, each change can be marked with an extension to explicitly state the conformance of the change. 4.3. Algorithm variants support Tools implementing schema comparison SHOULD support comparing locally resolved modules, fully resolved schemas, and both representations together. In case the comparison generates YANG data for the "ietf- yang-schema-comparison-output" YANG module, simple XPath filters can be used to select any subset of changes. Data definition statements are present in both the locally resolved module and fully resolved schema. So if both representations are compared normally, there would be duplicate changes reported in the algorithm output. These duplicate changes MUST be avoided and filtered out. 5. Schema Comparison YANG Module YANG module with extensions for fine-tuning the classification of differences between two revisions of YANG schemas. file "ietf-yang-schema-comparison@2026-09-02.yang" module ietf-yang-schema-comparison { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison"; prefix yscmp; organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG List: NETMOD WG list WG Web: https://datatracker.ietf.org/wg/netmod Author: Michal Vaško Author: Rob Wilton Author: Per Andersson "; description "This YANG 1.1 module contains extensions to support comparison between different versions of YANG schemas. Vaško, et al. Expires 25 April 2027 [Page 11] Internet-Draft YANG Schema Comparison October 2026 Copyright (c) 2026 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX (inc above) with actual RFC number and // remove this note. revision 2026-09-02 { description "Initial revision."; reference "RFC XXXX: YANG Schema Comparison"; } extension ed-change-at { argument semver; description "Marks statements in a new revision of a module that introduces an editorial change of the statement. The argument marks the most recent version of the module where the statement has been changed. Can only be a substatement of 'pattern', 'when', 'must', 'description', 'reference', 'presence', or extension instance statements."; reference "RFC 7950: The YANG 1.1 Data Modeling Language, section 11; RFC 6020: YANG - A Data Modeling Language for the Network Vaško, et al. Expires 25 April 2027 [Page 12] Internet-Draft YANG Schema Comparison October 2026 Configuration Protocol (NETCONF), section 10"; } extension bc-change-at { argument semver; description "Marks statements in a new revision of a module that introduces a backwards-compatible change of the statement. The argument marks the most recent version of the module where the statement has been changed. Can only be a substatement of 'pattern', 'when', 'must', 'description', 'reference', 'presence', or extension instance statements."; reference "RFC 7950: The YANG 1.1 Data Modeling Language, section 11; RFC 6020: YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF), section 10"; } extension nbc-change-at { argument semver; description "Marks statements in a new revision of a module that introduces a non-backwards-compatible change of the statement. The argument marks the most recent version of the module where the statement has been changed. Can only be a substatement of 'pattern', 'when', 'must', 'description', 'reference', 'presence', or extension instance statements."; reference "RFC 7950: The YANG 1.1 Data Modeling Language, section 11; RFC 6020: YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF), section 10"; } } Vaško, et al. Expires 25 April 2027 [Page 13] Internet-Draft YANG Schema Comparison October 2026 6. Contributors This document grew out of the YANG module versioning design team that was formed after IETF 101. The following individuals are (or have been) members of the design team and have contributed on the YANG versioning project: * Balazs Lengyel * Benoit Claise * Bo Wu * Ebben Aries * Jason Sterne * Joe Clarke * Juergen Schoenwaelder * Mahesh Jethanandani * Michael Wang * Qin Wu * Reshad Rahman * Rob Wilton * Jan Lindblad * Per Andersson The idea of a tooling-based comparison of YANG module revisions was first described in [I-D.clacla-netmod-yang-model-update]. This document builds on those initial ideas. 7. Security Considerations This section is modeled after the template described in Section 3.7.1 of [RFC9907]. Vaško, et al. Expires 25 April 2027 [Page 14] Internet-Draft YANG Schema Comparison October 2026 The YANG modules specified in this document define extensions ("ietf- yang-schema-comparison") and a schema for data ("ietf-yang-schema- comparison-output") that are designed to be used by offline tooling to generate output describing the differences between two supplied YANG modules. The YANG module specified in this document MAY be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to- implement secure transport is TLS [RFC8446]. The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. When the module is used by offline tooling, there are no security considerations, since the user has full access to all YANG modules being used. The "schema-comparison" structure defined in the "ietf-yang-schema- comparison-output" module contains all the groupings reflecting the changes between YANG modules. If instances of this structure are generated or published by online tooling, care needs to be taken so that information about non-public YANG modules is not inadvertently disclosed. Since the module does not define any RPCs, actions, or notifications, the security considerations for such statements are not provided here. 8. IANA Considerations 8.1. The "IETF XML" Registry This document registers two URIs in the "ns" subregistry of the IETF XML Registry [RFC3688] maintained at https://www.iana.org/assignments/xml-registry/xml-registry.xhtml#ns. Following the format defined in [RFC3688], the following registrations are requested: Vaško, et al. Expires 25 April 2027 [Page 15] Internet-Draft YANG Schema Comparison October 2026 URI: urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison-output Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. 8.2. The "YANG Module Names" Registry This document registers two YANG modules in the YANG Module Names registry [RFC6020] maintained at https://www.iana.org/assignments/ yang-parameters/yang-paramaters.xhtml. Following the format defined in [RFC6020], the following registrations are requested: Name: ietf-yang-schema-comparison XML Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison Prefix: schema-cmp Reference: RFC XXXX Name: ietf-yang-schema-comparison-output XML Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison-output Prefix: schema-cmp-out Reference: RFC XXXX 9. References 9.1. Normative References [I-D.ietf-netmod-yang-module-versioning] Wilton, R., Rahman, R., Lengyel, B., Clarke, J., and J. Sterne, "Updated YANG Module Revision Handling", Work in Progress, Internet-Draft, draft-ietf-netmod-yang-module- versioning-17, 29 June 2026, . [I-D.ietf-netmod-yang-packages] Wilton, R., Rahman, R., Clarke, J., and J. Sterne, "YANG Packages", Work in Progress, Internet-Draft, draft-ietf- netmod-yang-packages-10, 20 October 2026, . [I-D.ietf-netmod-yang-semver] Clarke, J., Wilton, R., Rahman, R., Lengyel, B., Sterne, J., and B. Claise, "YANG Semantic Versioning", Work in Progress, Internet-Draft, draft-ietf-netmod-yang-semver- Vaško, et al. Expires 25 April 2027 [Page 16] Internet-Draft YANG Schema Comparison October 2026 29, 6 October 2026, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Vaško, et al. Expires 25 April 2027 [Page 17] Internet-Draft YANG Schema Comparison October 2026 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, March 2019, . [RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data Structure Extensions", RFC 8791, DOI 10.17487/RFC8791, June 2020, . [RFC9907] Bierman, A., Boucadair, M., Ed., and Q. Wu, "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 9907, DOI 10.17487/RFC9907, March 2026, . 9.2. Informative References [I-D.clacla-netmod-yang-model-update] Claise, B., Clarke, J., Lengyel, B., and K. D'Souza, "New YANG Module Update Procedure", Work in Progress, Internet- Draft, draft-clacla-netmod-yang-model-update-06, 2 July 2018, . Appendix A. Schema Comparison Algorithm Output YANG Module This YANG module defines the specific output of the schema comparison algorithm, supporting comparison of the locally resolved module, fully resolved schema, or both. The "ietf-yang-schema-comparison- output" YANG module imports definitions from the "ietf-yang-types" module defined in [RFC6991], the "ietf-yang-library" module defined in [RFC8525], and the "ietf-yang-structure-ext" module defined in [RFC8791]. Generating schema comparison data in the form of YANG instance data compliant with this YANG module is optional but makes it easier for further automatic processing by tools and also allows for simple filtering of the data. Vaško, et al. Expires 25 April 2027 [Page 18] Internet-Draft YANG Schema Comparison October 2026 Non data definition statements are uniquely identified with their YANG identifier and data definition statements with their absolute schema node-ids. For every change, the changed statement and the parent of the changed statement are included. While redundant in many cases, it allows the algorithm to uniquely report changes in nested statements, e.g. an extension instance change in the type of a leaf statement. Also, all the unchanged substatements with their value or content are included for every changed statement, for both the older and the newer revision of the YANG module, if applicable. This ensures that the output includes all the possibly required information without relying on learning it from the YANG modules themselves. file "ietf-yang-schema-comparison-output@2026-09-02.yang" module ietf-yang-schema-comparison-output { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-schema-comparison-output"; prefix yscmp-out; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data types"; } import ietf-yang-library { prefix yanglib; reference "RFC 8525: YANG Library"; } import ietf-yang-structure-ext { prefix sx; reference "RFC 8791: YANG Data Structure Extensions"; } import ietf-yang-semver { prefix ysv; reference "RFC XXXX: YANG Semantic Versioning"; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG List: NETMOD WG list WG Web: https://datatracker.ietf.org/wg/netmod Author: Michal Vaško Vaško, et al. Expires 25 April 2027 [Page 19] Internet-Draft YANG Schema Comparison October 2026 Author: Rob Wilton Author: Per Andersson "; description "This YANG 1.1 module contains definitions of output of comparison between different versions of YANG schemas. The base schema nodes describe changes in a compiled YANG module with all of its included submodules and imported modules. The rest of the schema nodes are optional and describe changes in all the statements of a single YANG module. Copyright (c) 2026 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX (inc above) with actual RFC number and // remove this note. revision 2026-09-02 { description "Initial revision."; reference "RFC XXXX: YANG Schema Comparison"; } Vaško, et al. Expires 25 April 2027 [Page 20] Internet-Draft YANG Schema Comparison October 2026 typedef schema-node-path { type string; description "Node schema path (node-id). A generic type is used to not enforce their evaluation or validation in this context."; } typedef schema-stmt-path { type string; description "Path to a statement. Any non data node parents are encoded specially."; } typedef stmt-type { type enumeration { enum base { description "YANG statement 'base'."; } enum bit { description "YANG statement 'bit'."; } enum config { description "YANG statement 'config'."; } enum contact { description "YANG statement 'contact'."; } enum default { description "YANG statement 'default'."; } enum description { description "YANG statement 'description'."; } enum enum { description "YANG statement 'enum'."; } enum error-app-tag { description "YANG statement 'error-app-tag'."; } Vaško, et al. Expires 25 April 2027 [Page 21] Internet-Draft YANG Schema Comparison October 2026 enum error-message { description "YANG statement 'error-message'."; } enum extension { description "YANG statement 'extension'."; } enum extension-instance { description "Any extension instance YANG statement."; } enum feature { description "YANG statement 'feature'."; } enum fraction-digits { description "YANG statement 'fraction-digits'."; } enum identity { description "YANG statement 'identity'."; } enum if-feature { description "YANG statement 'if-feature'."; } enum import { description "YANG statement 'import'."; } enum include { description "YANG statement 'include'."; } enum length { description "YANG statement 'length'."; } enum mandatory { description "YANG statement 'mandatory'."; } enum max-elements { description "YANG statement 'max-elements'."; } Vaško, et al. Expires 25 April 2027 [Page 22] Internet-Draft YANG Schema Comparison October 2026 enum min-elements { description "YANG statement 'min-elements'."; } enum must { description "YANG statement 'must'."; } enum node { description "YANG statement 'container', 'leaf', 'leaf-list', 'list', 'anydata', 'anyxml', 'rpc', 'action', or 'notification'. If the locally resolved module is also compared, it can additionally be 'choice', 'case', 'input', 'output', 'uses', 'augment', or 'grouping'."; } enum ordered-by { description "YANG statement 'ordered-by'."; } enum organization { description "YANG statement 'organization'."; } enum path { description "YANG statement 'path'."; } enum pattern { description "YANG statement 'pattern'."; } enum prefix { description "YANG statement 'prefix'."; } enum presence { description "YANG statement 'presence'."; } enum range { description "YANG statement 'range'."; } enum reference { description "YANG statement 'reference'."; } Vaško, et al. Expires 25 April 2027 [Page 23] Internet-Draft YANG Schema Comparison October 2026 enum refine { description "YANG statement 'refine'."; } enum require-instance { description "YANG statement 'require-instance'."; } enum revision-date { description "YANG statement 'revision-date'."; } enum status { description "YANG statement 'status'."; } enum type { description "YANG statement 'type'."; } enum typedef { description "YANG statement 'typedef'."; } enum units { description "YANG statement 'units'."; } enum unique { description "YANG statement 'unique'."; } enum when { description "YANG statement 'when'."; } enum yang-version { description "YANG statement 'yang-version'."; } } description "Type of the statement that a change affects."; } typedef revision-or-empty { type union { type empty; Vaško, et al. Expires 25 April 2027 [Page 24] Internet-Draft YANG Schema Comparison October 2026 type yanglib:revision-identifier; } description "Module or submodule revision. If it has none, an empty value is used."; } grouping if-feature-stmts { description "Describes changes of all the if-features on a statement."; leaf-list if-feature { type string; description "Value of an if-feature statement."; } } grouping ext-instance-stmt { description "Describes changes of an extension instance."; leaf module { type yang:yang-identifier; mandatory true; description "Module with the extension definition of an extension instance."; } leaf name { type yang:yang-identifier; mandatory true; description "Name of the extension definition of an extension instance."; } leaf argument { type string; description "Argument used of an extension definition."; } anydata substatements { description "Any substatements of the extension instance."; } } grouping ext-instance-stmts { description "Describes changes of all the extension instances."; list ext-instance { description Vaško, et al. Expires 25 April 2027 [Page 25] Internet-Draft YANG Schema Comparison October 2026 "List of extension-instance substatements."; uses ext-instance-stmt; } } grouping status-stmt { description "Describes a status statement change."; leaf status { type enumeration { enum current { description "Current effective status of a statement."; } enum deprecated { description "Deprecated effective status of a statement."; } enum obsolete { description "Obsolete effective status of a statement."; } } mandatory true; description "Status substatement value."; } } grouping must-stmts { description "Describes changes of all the must statements of a specific parent statement."; list must { description "List of must substatements."; leaf condition { type string; description "Condition substatement value."; } uses restriction-substmts; } } grouping when-stmts { description "Describes changes of all the when statements of a specific parent Vaško, et al. Expires 25 April 2027 [Page 26] Internet-Draft YANG Schema Comparison October 2026 statement."; list when { description "List of when substatements."; leaf condition { type string; description "Condition substatement value."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses status-stmt; uses ext-instance-stmts; } } grouping restriction-substmts { description "Common substatements shared by all restriction statements."; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } leaf error-message { type string; description "Error-message substatement value."; } leaf error-app-tag { type string; description "Error-app-tag substatement value."; } uses ext-instance-stmts; Vaško, et al. Expires 25 April 2027 [Page 27] Internet-Draft YANG Schema Comparison October 2026 } grouping type-substmts { description "Describes a type statement change."; leaf base-type { type enumeration { enum int8 { description "YANG built-in type 'int8'."; } enum int16 { description "YANG built-in type 'int16'."; } enum int32 { description "YANG built-in type 'int32'."; } enum int64 { description "YANG built-in type 'int64'."; } enum uint8 { description "YANG built-in type 'uint8'."; } enum uint16 { description "YANG built-in type 'uint16'."; } enum uint32 { description "YANG built-in type 'uint32'."; } enum uint64 { description "YANG built-in type 'uint64'."; } enum decimal64 { description "YANG built-in type 'decimal64'."; } enum string { description "YANG built-in type 'string'."; } enum boolean { Vaško, et al. Expires 25 April 2027 [Page 28] Internet-Draft YANG Schema Comparison October 2026 description "YANG built-in type 'boolean'."; } enum enumeration { description "YANG built-in type 'enumeration'."; } enum bits { description "YANG built-in type 'bits'."; } enum binary { description "YANG built-in type 'binary'."; } enum leafref { description "YANG built-in type 'leafref'."; } enum identityref { description "YANG built-in type 'identityref'."; } enum empty { description "YANG built-in type 'empty'."; } enum union { description "YANG built-in type 'union'."; } enum instance-identifier { description "YANG built-in type 'instance-identifier'."; } } description "Type substatement value."; } container range { description "Range statement substatements."; list interval { description "Intervals of a range statement."; leaf min { type int64; description Vaško, et al. Expires 25 April 2027 [Page 29] Internet-Draft YANG Schema Comparison October 2026 "Lower boundary of an interval of a range statement."; } leaf max { type int64; description "Upper boundary of an interval of a range statement."; } } uses restriction-substmts; } container length { description "Length statement substatements."; list interval { description "Intervals of a length statement."; leaf min { type uint64; description "Lower boundary of an interval of a length statement."; } leaf max { type uint64; description "Upper boundary of an interval of a length statement."; } } uses restriction-substmts; } leaf fraction-digits { type uint8; description "Fraction-digits substatement value."; } list pattern { description "List of pattern statements."; leaf expression { type string; description "Pattern substatement value."; } leaf inverted { type boolean; description "A value of true indicates that the pattern's 'modifier' substatement is 'invert-match'."; reference Vaško, et al. Expires 25 April 2027 [Page 30] Internet-Draft YANG Schema Comparison October 2026 "RFC 7950 Section 9.4.6"; } uses restriction-substmts; } list enum { key "name"; ordered-by user; description "List of enum statements. Keeps the same order of the statements as in the module."; leaf name { type yang:yang-identifier; description "Enum statement name."; } uses if-feature-stmts { description "Populated only for locally resolved module."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } leaf value { type int32; description "Value substatement value."; } uses status-stmt; uses ext-instance-stmts; } list bit { key "name"; ordered-by user; description "List of bit statements. Keeps the same order of the statements as in the module."; leaf name { type yang:yang-identifier; description "Bit statement name."; } Vaško, et al. Expires 25 April 2027 [Page 31] Internet-Draft YANG Schema Comparison October 2026 uses if-feature-stmts { description "Populated only for locally resolved module."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } leaf position { type uint32; description "Position substatement value."; } uses status-stmt; uses ext-instance-stmts; } leaf path { type string; description "Path substatement value."; } leaf require-instance { type boolean; description "Require-instance substatement value."; } leaf-list base { type yang:yang-identifier; description "List of base substatement values."; } uses ext-instance-stmts; } grouping type-local-substmts { description "Describes a locally resolved module type statement change."; leaf name { type yang:yang-identifier; description "Type argument substatement value."; } Vaško, et al. Expires 25 April 2027 [Page 32] Internet-Draft YANG Schema Comparison October 2026 container range { description "Range statement substatements."; leaf restriction { type string; description "Range argument substatement value."; } uses restriction-substmts; } container length { description "Length statement substatements."; leaf restriction { type string; description "Length argument substatement value."; } uses restriction-substmts; } leaf fraction-digits { type uint8; description "Fraction-digits substatement value."; } list pattern { description "List of pattern statements."; leaf expression { type string; description "Pattern substatement value."; } leaf inverted { type empty; description "Presence indicates that the pattern's 'modifier' substatement is 'invert-match'."; reference "RFC 7950 Section 9.4.6"; } uses restriction-substmts; } list enum { key "name"; ordered-by user; description "List of enum statements. Keeps the same order of the statements Vaško, et al. Expires 25 April 2027 [Page 33] Internet-Draft YANG Schema Comparison October 2026 as in the module."; leaf name { type yang:yang-identifier; description "Enum statement name."; } uses if-feature-stmts; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } leaf value { type int32; description "Value substatement value."; } uses status-stmt; uses ext-instance-stmts; } list bit { key "name"; ordered-by user; description "List of bit statements. Keeps the same order of the statements as in the module."; leaf name { type yang:yang-identifier; description "Bit statement name."; } uses if-feature-stmts; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } leaf position { Vaško, et al. Expires 25 April 2027 [Page 34] Internet-Draft YANG Schema Comparison October 2026 type uint32; description "Position substatement value."; } uses status-stmt; uses ext-instance-stmts; } leaf path { type string; description "Path substatement value."; } leaf require-instance { type boolean; description "Require-instance substatement value."; } leaf-list base { type yang:yang-identifier; description "List of base substatement values."; } uses ext-instance-stmts; } grouping refine-node-substmts { description "All substatements of a data-definition node that can be changed by a refine statement."; uses must-stmts; leaf-list default { type string; description "List of default substatement values."; } leaf config { type boolean; description "Config substatement value."; } leaf mandatory { type boolean; description "Mandatory substatement value."; } leaf min-elements { type uint32; description Vaško, et al. Expires 25 April 2027 [Page 35] Internet-Draft YANG Schema Comparison October 2026 "Min-elements substatement value."; } leaf max-elements { type uint32; description "Max-elements substatement value."; } } grouping node-substmts { description "All substatements of a data-definition node."; uses if-feature-stmts { when "../../locally-resolved"; } uses when-stmts; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses status-stmt; uses refine-node-substmts; leaf-list key { type yang:yang-identifier; description "Leaf-list of nodes referenced by a key statement."; } leaf ordered-by { type enumeration { enum system { description "System-ordered list or leaf-list of items."; } enum user { description "User-ordered list or leaf-list of items."; } } description "Ordered-by substatement value."; } container type { Vaško, et al. Expires 25 April 2027 [Page 36] Internet-Draft YANG Schema Comparison October 2026 description "Type substatement."; uses type-substmts; list union-type { description "List of a union type substatements."; uses type-substmts; } } leaf units { type string; description "Units substatement value."; } list unique { description "List of unique substatements."; leaf-list node { type yang:yang-identifier; description "List of nodes referenced by a unique substatement."; } } leaf presence { type boolean; description "Indicates whether a presence substatement is defined for the container in the compiled schema. The textual argument of 'presence' is reported via the locally resolved module comparison (see the 'presence' leaf in 'local-substmts')."; } uses ext-instance-stmts; } grouping module-substmts { description "All non-data-definition substatements of a module."; leaf yang-version { type string; description "YANG version substatement value."; } leaf prefix { when "../../../locally-resolved"; type string; description "Prefix substatement value."; } Vaško, et al. Expires 25 April 2027 [Page 37] Internet-Draft YANG Schema Comparison October 2026 container import { when "../../../locally-resolved"; presence "Exists only when there is a difference in this import."; description "Import substatements."; leaf module { type yang:yang-identifier; mandatory true; description "Imported module."; } leaf prefix { type yang:yang-identifier; mandatory true; description "Imported module prefix."; } leaf revision-date { type yanglib:revision-identifier; description "Imported module revision-date."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses ext-instance-stmts; } container include { when "../../../locally-resolved"; presence "Exists only when there is a difference in this include."; description "Include substatements."; leaf submodule { type yang:yang-identifier; mandatory true; description "Included submodule."; } leaf revision-date { type yanglib:revision-identifier; Vaško, et al. Expires 25 April 2027 [Page 38] Internet-Draft YANG Schema Comparison October 2026 description "Included submodule revision-date."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses ext-instance-stmts; } leaf organization { type string; description "Organization substatement value."; } leaf contact { type string; description "Contact substatement value."; } leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } container extension { when "../../../locally-resolved"; presence "Exists only when there is a difference in this extension."; description "Extension substatements."; leaf name { type yang:yang-identifier; mandatory true; description "Extension name."; } leaf argument { Vaško, et al. Expires 25 April 2027 [Page 39] Internet-Draft YANG Schema Comparison October 2026 type yang:yang-identifier; description "Argument substatement value."; } uses status-stmt; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses ext-instance-stmts; } container feature { when "../../../locally-resolved"; presence "Exists only when there is a difference in this feature."; description "Feature substatements."; leaf name { type yang:yang-identifier; mandatory true; description "Feature name."; } uses if-feature-stmts; uses status-stmt; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses ext-instance-stmts; } container identity { description "Identity substatements."; leaf name { type yang:yang-identifier; Vaško, et al. Expires 25 April 2027 [Page 40] Internet-Draft YANG Schema Comparison October 2026 mandatory true; description "Identity statement name."; } uses if-feature-stmts { when "../../../locally-resolved"; } leaf-list base { when "../../../../locally-resolved"; type yang:yang-identifier; description "List of bases of an identity."; } uses ext-instance-stmts; } container ext-instance { presence "Exists only when there is a difference in this extension-instance."; description "Extension-instance substatements."; uses ext-instance-stmt; } } grouping local-substmts { description "All locally-resolved-module-only statements that can be direct substatements of a module or nested in a node."; uses if-feature-stmts; uses when-stmts; leaf description { type string; description "Description substatement value."; } leaf reference { type string; description "Reference substatement value."; } uses status-stmt; uses refine-node-substmts; container type { description "Type substatement."; uses type-local-substmts; list union-type { Vaško, et al. Expires 25 April 2027 [Page 41] Internet-Draft YANG Schema Comparison October 2026 description "List of a union type substatements."; uses type-local-substmts; } } leaf units { type string; description "Units substatement value."; } leaf presence { type string; description "Presence substatement value."; } uses ext-instance-stmts; } grouping conformance-type { description "Conformance type of a change."; leaf conformance { type enumeration { enum editorial { description "Editorial change."; } enum backwards-compatible { description "Backwards-compatible change."; } enum non-backwards-compatible { description "Non-backwards-compatible change."; } } mandatory true; description "Conformance information of a change in the compared YANG modules."; } } grouping change-info { description "Details of a single change."; list changed { key "stmt"; Vaško, et al. Expires 25 April 2027 [Page 42] Internet-Draft YANG Schema Comparison October 2026 min-elements 1; description "List of changes."; leaf stmt { type stmt-type; description "Changed statement."; } leaf parent-stmt { type stmt-type; description "Parent statement of the changed statement."; } leaf change { type enumeration { enum modified { description "Statement existed and was modified."; } enum added { description "Statement was added."; } enum removed { description "Statement was removed."; } enum moved { description "Statement was moved and the position affects the meaning."; } } mandatory true; description "Type of change of the statement."; } uses conformance-type; } } grouping module-params { description "Identification details of a processed YANG module."; leaf module { type yang:yang-identifier; description "Compared module name."; Vaško, et al. Expires 25 April 2027 [Page 43] Internet-Draft YANG Schema Comparison October 2026 } leaf revision { type revision-or-empty; description "Compared module revision."; } leaf version { type ysv:version; description "Compared module semantic version, if defined."; } list submodule { key "name revision"; leaf name { type yang:yang-identifier; description "Submodule name."; } leaf revision { type revision-or-empty; description "Submodule revision."; } description "Submodule of the main module."; } leaf-list enabled-feature { type yang:yang-identifier; description "All the enabled features of the module."; } } grouping local-info { description "Information about all the changed locally-resolved-module-only statements."; list local-comparison { description "Information about locally-resolved-module-only statement changes."; leaf parent-path { type schema-stmt-path; description "Path to the parent statement. Not set if a direct substatement of module or submodule."; } leaf identifier { type string; mandatory true; Vaško, et al. Expires 25 April 2027 [Page 44] Internet-Draft YANG Schema Comparison October 2026 description "Identifier of the statement, may include a prefix."; } leaf stmt-type { type enumeration { enum choice { description "YANG statement 'choice' node."; } enum case { description "YANG statement 'case' node."; } enum input { description "YANG statement 'input' node."; } enum output { description "YANG statement 'output' node."; } enum uses { description "YANG statement 'uses' node."; } enum grouping { description "YANG statement 'grouping' node."; } enum augment { description "YANG statement 'augment' node."; } enum refine { description "YANG statement 'refine' node."; } enum typedef { description "YANG statement 'typedef'."; } } mandatory true; description "Type of the changed data-definition statement."; } uses change-info; container old { Vaško, et al. Expires 25 April 2027 [Page 45] Internet-Draft YANG Schema Comparison October 2026 description "Changed local statements in the older revision of the YANG module."; uses local-substmts; } container new { description "Changed local statements in the newer revision of the YANG module."; uses local-substmts; } } } grouping node-info { description "Information about all the changed nodes."; list node-comparison { key "node"; ordered-by user; description "Information about data-definition (node) statement substatement changes. Keeps the traversed order of the nodes by the algorithm. It SHOULD follow the depth-first search order."; leaf node { type schema-node-path; description "Path to the changed data-definition statement."; } leaf node-type { type enumeration { enum container { description "YANG statement 'container' node."; } enum leaf { description "YANG statement 'leaf' node."; } enum leaf-list { description "YANG statement 'leaf-list' node."; } enum list { description "YANG statement 'list' node."; } enum anydata { Vaško, et al. Expires 25 April 2027 [Page 46] Internet-Draft YANG Schema Comparison October 2026 description "YANG statement 'anydata' node."; } enum anyxml { description "YANG statement 'anyxml' node."; } enum rpc { description "YANG statement 'rpc' node."; } enum action { description "YANG statement 'action' node."; } enum notification { description "YANG statement 'notification' node."; } } mandatory true; description "Type of the changed data-definition statement."; } uses change-info; container old { description "All the node substatements in the older revision of the YANG module."; uses node-substmts; } container new { description "All the node substatements in the newer revision of the YANG module."; uses node-substmts; } } } sx:structure schema-comparison { description "Schema comparison details."; list comparison { must "locally-resolved or fully-resolved" { description "As the comparison input, locally resolved module, fully resolved module, or both must be used."; Vaško, et al. Expires 25 April 2027 [Page 47] Internet-Draft YANG Schema Comparison October 2026 } description "Instance of a schema comparison of 2 YANG modules in different revisions with all their imports."; leaf locally-resolved { type empty; description "Locally resolved module has been used for the comparison."; reference "RFC XXXX Section 3.1."; } leaf fully-resolved { type empty; description "Fully resolved schema has been used for the comparison."; reference "RFC XXXX Section 3.2."; } container source { description "Source module information."; uses module-params; } list source-import { when "../fully-resolved"; key "module revision"; description "List of source module imported modules information."; uses module-params; } container target { description "Target module information."; uses module-params; } list target-import { when "../fully-resolved"; key "module revision"; description "List of target module imported modules information."; uses module-params; } uses conformance-type; list module-comparison { description "Information about direct module statement substatement changes."; uses change-info; Vaško, et al. Expires 25 April 2027 [Page 48] Internet-Draft YANG Schema Comparison October 2026 container old { description "Changed statements in the older revision of the YANG module."; uses module-substmts; } container new { description "Changed statements in the newer revision of the YANG module."; uses module-substmts; } } uses local-info { when "locally-resolved"; } uses node-info; } } } A.1. Tree diagram The “ietf-yang-schema-comparison-output” YANG module has the following structure: module: ietf-yang-schema-comparison-output structure schema-comparison: +-- comparison* +-- locally-resolved? empty +-- fully-resolved? empty +-- source | +-- module? yang:yang-identifier | +-- revision? revision-or-empty | +-- version? ysv:version | +-- submodule* [name revision] | | +-- name yang:yang-identifier | | +-- revision revision-or-empty | +-- enabled-feature* yang:yang-identifier +-- source-import* [module revision] | +-- module yang:yang-identifier | +-- revision revision-or-empty | +-- version? ysv:version | +-- submodule* [name revision] | | +-- name yang:yang-identifier | | +-- revision revision-or-empty Vaško, et al. Expires 25 April 2027 [Page 49] Internet-Draft YANG Schema Comparison October 2026 | +-- enabled-feature* yang:yang-identifier +-- target | +-- module? yang:yang-identifier | +-- revision? revision-or-empty | +-- version? ysv:version | +-- submodule* [name revision] | | +-- name yang:yang-identifier | | +-- revision revision-or-empty | +-- enabled-feature* yang:yang-identifier +-- target-import* [module revision] | +-- module yang:yang-identifier | +-- revision revision-or-empty | +-- version? ysv:version | +-- submodule* [name revision] | | +-- name yang:yang-identifier | | +-- revision revision-or-empty | +-- enabled-feature* yang:yang-identifier +-- conformance enumeration +-- suggested-target-version ysv:version +-- module-comparison* | +-- changed* [stmt] | | +-- stmt stmt-type | | +-- parent-stmt? stmt-type | | +-- change enumeration | | +-- conformance enumeration | +-- old | | +-- yang-version? string | | +-- prefix? string | | +-- import! | | | +-- module yang:yang-identifier | | | +-- prefix yang:yang-identifier | | | +-- revision-date? yanglib:revision-identifier | | | +-- description? string | | | +-- reference? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- include! | | | +-- submodule yang:yang-identifier | | | +-- revision-date? yanglib:revision-identifier | | | +-- description? string | | | +-- reference? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string Vaško, et al. Expires 25 April 2027 [Page 50] Internet-Draft YANG Schema Comparison October 2026 | | | +-- substatements? anydata | | +-- organization? string | | +-- contact? string | | +-- description? string | | +-- reference? string | | +-- extension! | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- status enumeration | | | +-- description? string | | | +-- reference? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- feature! | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- status enumeration | | | +-- description? string | | | +-- reference? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- identity | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- base* string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- deviation! | | | +-- target string | | | +-- deviate* | | | | +-- argument enumeration | | | | +-- must* | | | | | +-- condition? string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier Vaško, et al. Expires 25 April 2027 [Page 51] Internet-Draft YANG Schema Comparison October 2026 | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- default* string | | | | +-- config? boolean | | | | +-- mandatory? boolean | | | | +-- min-elements? uint32 | | | | +-- max-elements? uint32 | | | | +-- type | | | | | +-- name? string | | | | | +-- range | | | | | | +-- restriction? string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- length | | | | | | +-- restriction? string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- fraction-digits? uint8 | | | | | +-- pattern* | | | | | | +-- expression? string | | | | | | +-- inverted? boolean | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- enum* [name] | | | | | | +-- name yang:yang-identifier | | | | | | +-- if-feature* string Vaško, et al. Expires 25 April 2027 [Page 52] Internet-Draft YANG Schema Comparison October 2026 | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- value? int32 | | | | | | +-- status enumeration | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- bit* [name] | | | | | | +-- name yang:yang-identifier | | | | | | +-- if-feature* string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- position? uint32 | | | | | | +-- status enumeration | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- path? string | | | | | +-- require-instance? boolean | | | | | +-- base* string | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- union-type* | | | | | +-- name? string | | | | | +-- range | | | | | | +-- restriction? string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- length | | | | | | +-- restriction? string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string Vaško, et al. Expires 25 April 2027 [Page 53] Internet-Draft YANG Schema Comparison October 2026 | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- fraction-digits? uint8 | | | | | +-- pattern* | | | | | | +-- expression? string | | | | | | +-- inverted? boolean | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- error-message? string | | | | | | +-- error-app-tag? string | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- enum* [name] | | | | | | +-- name yang:yang-identifier | | | | | | +-- if-feature* string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- value? int32 | | | | | | +-- status enumeration | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- bit* [name] | | | | | | +-- name yang:yang-identifier | | | | | | +-- if-feature* string | | | | | | +-- description? string | | | | | | +-- reference? string | | | | | | +-- position? uint32 | | | | | | +-- status enumeration | | | | | | +-- ext-instance* | | | | | | +-- module yang:yang-identifier | | | | | | +-- name yang:yang-identifier | | | | | | +-- argument? string | | | | | | +-- substatements? anydata | | | | | +-- path? string | | | | | +-- require-instance? boolean | | | | | +-- base* string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier Vaško, et al. Expires 25 April 2027 [Page 54] Internet-Draft YANG Schema Comparison October 2026 | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- units? string | | | | +-- unique* | | | | +-- node* yang:yang-identifier | | | +-- description? string | | | +-- reference? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- ext-instance! | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- new | +-- yang-version? string | +-- prefix? string | +-- import! | | +-- module yang:yang-identifier | | +-- prefix yang:yang-identifier | | +-- revision-date? yanglib:revision-identifier | | +-- description? string | | +-- reference? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- include! | | +-- submodule yang:yang-identifier | | +-- revision-date? yanglib:revision-identifier | | +-- description? string | | +-- reference? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- organization? string | +-- contact? string | +-- description? string | +-- reference? string | +-- extension! | | +-- name yang:yang-identifier | | +-- argument? string Vaško, et al. Expires 25 April 2027 [Page 55] Internet-Draft YANG Schema Comparison October 2026 | | +-- status enumeration | | +-- description? string | | +-- reference? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- feature! | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- status enumeration | | +-- description? string | | +-- reference? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- identity | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- base* string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- deviation! | | +-- target string | | +-- deviate* | | | +-- argument enumeration | | | +-- must* | | | | +-- condition? string | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- default* string | | | +-- config? boolean | | | +-- mandatory? boolean | | | +-- min-elements? uint32 | | | +-- max-elements? uint32 Vaško, et al. Expires 25 April 2027 [Page 56] Internet-Draft YANG Schema Comparison October 2026 | | | +-- type | | | | +-- name? string | | | | +-- range | | | | | +-- restriction? string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- length | | | | | +-- restriction? string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- fraction-digits? uint8 | | | | +-- pattern* | | | | | +-- expression? string | | | | | +-- inverted? boolean | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- enum* [name] | | | | | +-- name yang:yang-identifier | | | | | +-- if-feature* string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- value? int32 | | | | | +-- status enumeration | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string Vaško, et al. Expires 25 April 2027 [Page 57] Internet-Draft YANG Schema Comparison October 2026 | | | | | +-- substatements? anydata | | | | +-- bit* [name] | | | | | +-- name yang:yang-identifier | | | | | +-- if-feature* string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- position? uint32 | | | | | +-- status enumeration | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- path? string | | | | +-- require-instance? boolean | | | | +-- base* string | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- union-type* | | | | +-- name? string | | | | +-- range | | | | | +-- restriction? string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- length | | | | | +-- restriction? string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- fraction-digits? uint8 | | | | +-- pattern* | | | | | +-- expression? string Vaško, et al. Expires 25 April 2027 [Page 58] Internet-Draft YANG Schema Comparison October 2026 | | | | | +-- inverted? boolean | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- error-message? string | | | | | +-- error-app-tag? string | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- enum* [name] | | | | | +-- name yang:yang-identifier | | | | | +-- if-feature* string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- value? int32 | | | | | +-- status enumeration | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- bit* [name] | | | | | +-- name yang:yang-identifier | | | | | +-- if-feature* string | | | | | +-- description? string | | | | | +-- reference? string | | | | | +-- position? uint32 | | | | | +-- status enumeration | | | | | +-- ext-instance* | | | | | +-- module yang:yang-identifier | | | | | +-- name yang:yang-identifier | | | | | +-- argument? string | | | | | +-- substatements? anydata | | | | +-- path? string | | | | +-- require-instance? boolean | | | | +-- base* string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- units? string | | | +-- unique* | | | +-- node* yang:yang-identifier | | +-- description? string | | +-- reference? string | | +-- ext-instance* Vaško, et al. Expires 25 April 2027 [Page 59] Internet-Draft YANG Schema Comparison October 2026 | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- ext-instance! | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- local-comparison* | +-- parent-path? schema-stmt-path | +-- identifier string | +-- stmt-type enumeration | +-- changed* [stmt] | | +-- stmt stmt-type | | +-- parent-stmt? stmt-type | | +-- change enumeration | | +-- conformance enumeration | +-- old | | +-- if-feature* string | | +-- when* | | | +-- condition? string | | | +-- description? string | | | +-- reference? string | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- description? string | | +-- reference? string | | +-- status enumeration | | +-- must* | | | +-- condition? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- default* string | | +-- config? boolean | | +-- mandatory? boolean | | +-- min-elements? uint32 Vaško, et al. Expires 25 April 2027 [Page 60] Internet-Draft YANG Schema Comparison October 2026 | | +-- max-elements? uint32 | | +-- type | | | +-- name? string | | | +-- range | | | | +-- restriction? string | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- length | | | | +-- restriction? string | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- fraction-digits? uint8 | | | +-- pattern* | | | | +-- expression? string | | | | +-- inverted? boolean | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- enum* [name] | | | | +-- name yang:yang-identifier | | | | +-- if-feature* string | | | | +-- description? string | | | | +-- reference? string | | | | +-- value? int32 | | | | +-- status enumeration | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier Vaško, et al. Expires 25 April 2027 [Page 61] Internet-Draft YANG Schema Comparison October 2026 | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- bit* [name] | | | | +-- name yang:yang-identifier | | | | +-- if-feature* string | | | | +-- description? string | | | | +-- reference? string | | | | +-- position? uint32 | | | | +-- status enumeration | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- path? string | | | +-- require-instance? boolean | | | +-- base* string | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- union-type* | | | +-- name? string | | | +-- range | | | | +-- restriction? string | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- length | | | | +-- restriction? string | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- fraction-digits? uint8 | | | +-- pattern* Vaško, et al. Expires 25 April 2027 [Page 62] Internet-Draft YANG Schema Comparison October 2026 | | | | +-- expression? string | | | | +-- inverted? boolean | | | | +-- description? string | | | | +-- reference? string | | | | +-- error-message? string | | | | +-- error-app-tag? string | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- enum* [name] | | | | +-- name yang:yang-identifier | | | | +-- if-feature* string | | | | +-- description? string | | | | +-- reference? string | | | | +-- value? int32 | | | | +-- status enumeration | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- bit* [name] | | | | +-- name yang:yang-identifier | | | | +-- if-feature* string | | | | +-- description? string | | | | +-- reference? string | | | | +-- position? uint32 | | | | +-- status enumeration | | | | +-- ext-instance* | | | | +-- module yang:yang-identifier | | | | +-- name yang:yang-identifier | | | | +-- argument? string | | | | +-- substatements? anydata | | | +-- path? string | | | +-- require-instance? boolean | | | +-- base* string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- units? string | | +-- key? string | | +-- unique* string | | +-- presence? string | | +-- ext-instance* Vaško, et al. Expires 25 April 2027 [Page 63] Internet-Draft YANG Schema Comparison October 2026 | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- new | +-- if-feature* string | +-- when* | | +-- condition? string | | +-- description? string | | +-- reference? string | | +-- status enumeration | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- description? string | +-- reference? string | +-- status enumeration | +-- must* | | +-- condition? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- default* string | +-- config? boolean | +-- mandatory? boolean | +-- min-elements? uint32 | +-- max-elements? uint32 | +-- type | | +-- name? string | | +-- range | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata Vaško, et al. Expires 25 April 2027 [Page 64] Internet-Draft YANG Schema Comparison October 2026 | | +-- length | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- fraction-digits? uint8 | | +-- pattern* | | | +-- expression? string | | | +-- inverted? boolean | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- enum* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- value? int32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- bit* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- position? uint32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata Vaško, et al. Expires 25 April 2027 [Page 65] Internet-Draft YANG Schema Comparison October 2026 | | +-- path? string | | +-- require-instance? boolean | | +-- base* string | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- union-type* | | +-- name? string | | +-- range | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- length | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- fraction-digits? uint8 | | +-- pattern* | | | +-- expression? string | | | +-- inverted? boolean | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- enum* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string Vaško, et al. Expires 25 April 2027 [Page 66] Internet-Draft YANG Schema Comparison October 2026 | | | +-- description? string | | | +-- reference? string | | | +-- value? int32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- bit* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- position? uint32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- path? string | | +-- require-instance? boolean | | +-- base* string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- units? string | +-- key? string | +-- unique* string | +-- presence? string | +-- ext-instance* | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- node-comparison* [node] +-- node schema-node-path +-- node-type enumeration +-- changed* [stmt] | +-- stmt stmt-type | +-- parent-stmt? stmt-type | +-- change enumeration | +-- conformance enumeration +-- old | +-- if-feature* string Vaško, et al. Expires 25 April 2027 [Page 67] Internet-Draft YANG Schema Comparison October 2026 | +-- when* | | +-- condition? string | | +-- description? string | | +-- reference? string | | +-- status enumeration | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- description? string | +-- reference? string | +-- status enumeration | +-- must* | | +-- condition? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- default* string | +-- config? boolean | +-- mandatory? boolean | +-- min-elements? uint32 | +-- max-elements? uint32 | +-- key* yang:yang-identifier | +-- ordered-by? enumeration | +-- type | | +-- name? string | | +-- range | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- length | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string Vaško, et al. Expires 25 April 2027 [Page 68] Internet-Draft YANG Schema Comparison October 2026 | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- fraction-digits? uint8 | | +-- pattern* | | | +-- expression? string | | | +-- inverted? boolean | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- enum* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- value? int32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- bit* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- position? uint32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- path? string | | +-- require-instance? boolean | | +-- base* string | | +-- ext-instance* Vaško, et al. Expires 25 April 2027 [Page 69] Internet-Draft YANG Schema Comparison October 2026 | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- union-type* | | +-- name? string | | +-- range | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- length | | | +-- restriction? string | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- fraction-digits? uint8 | | +-- pattern* | | | +-- expression? string | | | +-- inverted? boolean | | | +-- description? string | | | +-- reference? string | | | +-- error-message? string | | | +-- error-app-tag? string | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- enum* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- value? int32 | | | +-- status enumeration Vaško, et al. Expires 25 April 2027 [Page 70] Internet-Draft YANG Schema Comparison October 2026 | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- bit* [name] | | | +-- name yang:yang-identifier | | | +-- if-feature* string | | | +-- description? string | | | +-- reference? string | | | +-- position? uint32 | | | +-- status enumeration | | | +-- ext-instance* | | | +-- module yang:yang-identifier | | | +-- name yang:yang-identifier | | | +-- argument? string | | | +-- substatements? anydata | | +-- path? string | | +-- require-instance? boolean | | +-- base* string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- units? string | +-- unique* | | +-- node* yang:yang-identifier | +-- presence? string | +-- ext-instance* | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- new +-- if-feature* string +-- when* | +-- condition? string | +-- description? string | +-- reference? string | +-- status enumeration | +-- ext-instance* | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- description? string +-- reference? string Vaško, et al. Expires 25 April 2027 [Page 71] Internet-Draft YANG Schema Comparison October 2026 +-- status enumeration +-- must* | +-- condition? string | +-- description? string | +-- reference? string | +-- error-message? string | +-- error-app-tag? string | +-- ext-instance* | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- default* string +-- config? boolean +-- mandatory? boolean +-- min-elements? uint32 +-- max-elements? uint32 +-- key* yang:yang-identifier +-- ordered-by? enumeration +-- type | +-- name? string | +-- range | | +-- restriction? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- length | | +-- restriction? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- fraction-digits? uint8 | +-- pattern* | | +-- expression? string | | +-- inverted? boolean | | +-- description? string Vaško, et al. Expires 25 April 2027 [Page 72] Internet-Draft YANG Schema Comparison October 2026 | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- enum* [name] | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- description? string | | +-- reference? string | | +-- value? int32 | | +-- status enumeration | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- bit* [name] | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- description? string | | +-- reference? string | | +-- position? uint32 | | +-- status enumeration | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- path? string | +-- require-instance? boolean | +-- base* string | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- union-type* | +-- name? string | +-- range | | +-- restriction? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string Vaško, et al. Expires 25 April 2027 [Page 73] Internet-Draft YANG Schema Comparison October 2026 | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- length | | +-- restriction? string | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- fraction-digits? uint8 | +-- pattern* | | +-- expression? string | | +-- inverted? boolean | | +-- description? string | | +-- reference? string | | +-- error-message? string | | +-- error-app-tag? string | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- enum* [name] | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- description? string | | +-- reference? string | | +-- value? int32 | | +-- status enumeration | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- bit* [name] | | +-- name yang:yang-identifier | | +-- if-feature* string | | +-- description? string | | +-- reference? string | | +-- position? uint32 | | +-- status enumeration Vaško, et al. Expires 25 April 2027 [Page 74] Internet-Draft YANG Schema Comparison October 2026 | | +-- ext-instance* | | +-- module yang:yang-identifier | | +-- name yang:yang-identifier | | +-- argument? string | | +-- substatements? anydata | +-- path? string | +-- require-instance? boolean | +-- base* string | +-- ext-instance* | +-- module yang:yang-identifier | +-- name yang:yang-identifier | +-- argument? string | +-- substatements? anydata +-- units? string +-- unique* | +-- node* yang:yang-identifier +-- presence? string +-- ext-instance* +-- module yang:yang-identifier +-- name yang:yang-identifier +-- argument? string +-- substatements? anydata Appendix B. Change Conformance Principles This appendix clarifies the general principles based on which statement changes are categorized. They are not meant to replace any specification but rather help with understanding it. B.1. Editorial change An editorial change does not affect valid YANG data of the semantics of the YANG module in any way. That is, it does not make the valid data value space smaller or larger and it must remain exactly the same as in the module revision without the change. Also, for a change to be editorial, it must not affect any YANG module importing the changed YANG module. In addition to obvious editorial changes such as fixing a typo in a "description", changing the local "prefix" of the module is also categorized as editorial because it does not affect importing modules. Or, replacing a "uses" statement directly with the nodes in the referenced "grouping" without any other changes. Vaško, et al. Expires 25 April 2027 [Page 75] Internet-Draft YANG Schema Comparison October 2026 B.2. Backwards-compatible change For a change to be backwards-compatible, it has to expand the value space of valid YANG data. That is, all the valid YANG data nodes and values before the change must remain valid but additional nodes or values can also become valid after the change. Also, backwards- compatible changes may influence importing modules but must not cause them to become invalid. In other words, they may expose new statements whose removal would then be considered a non-backwards- compatible change but generally must not change the already exposed statements. For some examples, the majority of possible backwards-compatible changes are specifically mentioned directly in Section 11 of [RFC7950]. B.3. Non-backwards-compatible change If a change is not editorial nor backwards-compatible, it is then categorized as non-backwards-compatible. Such changes shrink the value space of valid YANG data, causing some previously valid nodes or values to no longer be valid. Also, any change that may cause an importing module to become invalid according to the YANG specification must be non-backwards-compatible. Examples of less common or less obvious compatibility-breaking changes are changing the "yang-version" of a YANG module or expanding the size of a "type". The former change may break importing modules because of specific rules defined for the "import" statement and the target module's YANG version. Changing a "type" of a leaf from "uint32" to "uint64" may seem to fit the definition of a backwards- compatible change, but it may not be so for some data encodings that use a fixed binary data chunk (which would grow in size) or even a text format that may use a different encoding for the two types. Specifically, the JSON YANG data format [RFC7951] encodes a "uint32" value as a JSON number but a "uint64" as a JSON string. Appendix C. Comparison Examples This section provides several examples of the output from the comparison algorithm defined in this document to illustrate its behavior on actual YANG modules. The example YANG modules are missing “description” or “reference” statements for better readability. Changes are represented as JSON encoded [RFC7951] YANG instance data following the “ietf-yang-schema-comparison-output” module definition in Appendix A for the output. Vaško, et al. Expires 25 April 2027 [Page 76] Internet-Draft YANG Schema Comparison October 2026 C.1. New Leaves Module In this example, two new leaves are added to the module. In the generated output, there are changes in both locally resolved module and fully resolved schema. The changes are backward- compatible because the new nodes are added without affecting the order of the existing schema nodes. module mod1 { namespace "urn:mod1"; prefix m1; yang-version 1.1; revision 2025-01-01; container cont { leaf l1 { type string; } } } module mod1 { namespace "urn:mod1"; prefix m1; yang-version 1.1; revision 2025-06-01; revision 2025-01-01; container cont { leaf l1 { type string; } leaf l2 { type decimal64 { fraction-digits 4; } } } leaf l3 { type uint8; } } Vaško, et al. Expires 25 April 2027 [Page 77] Internet-Draft YANG Schema Comparison October 2026 { "ietf-yang-schema-comparison-output:schema-comparison": { "schema": [ { "source": { "module": "mod1", "revision": "2025-01-01" }, "target": { "module": "mod1", "revision": "2025-06-01" }, "conformance": "backwards-compatible", "node-comparison": [ { "node": "/mod1:cont/l2", "node-type": "leaf", "changed": [ { "stmt": "node", "change": "added", "conformance": "backwards-compatible" } ], "new": { "status": "current", "config": true, "mandatory": false, "type": { "base-type": "decimal64", "fraction-digits": 4 } } }, { "node": "/mod1:l3", "node-type": "leaf", "changed": [ { "stmt": "node", "change": "added", "conformance": "backwards-compatible" } ], "new": { "status": "current", "config": true, "mandatory": false, Vaško, et al. Expires 25 April 2027 [Page 78] Internet-Draft YANG Schema Comparison October 2026 "type": { "base-type": "uint8" } } } ] } ] } } C.2. Relaxed Length Module An example module comparison in which a typedef length restriction is relaxed and a new leaf is added. The generated diff includes both locally resolved and fully resolved changes. In the local comparison, the specific range change is reported as backward-compatible because the restriction was relaxed. In the fully resolved node comparison, the exact same change is reported because the leaf uses the same typedef, whose change also affects the leaf. The newly added leaf is also reported and marked as backward-compatible. module mod1 { namespace "urn:mod2"; prefix m2; yang-version 1.1; revision 2025-01-01; typedef my-string { type string { length "1..10"; } } container cont { leaf l { type my-string; } } } Vaško, et al. Expires 25 April 2027 [Page 79] Internet-Draft YANG Schema Comparison October 2026 module mod1 { namespace "urn:mod2"; prefix m2; yang-version 1.1; revision 2025-06-01; revision 2025-01-01; typedef my-string { type string { length "1..20"; } } container cont { leaf l { type my-string; } leaf l2 { type int32; } } } { "ietf-yang-schema-comparison-output:schema-comparison": { "schema": [ { "source": { "module": "mod2", "revision": "2025-01-01" }, "target": { "module": "mod2", "revision": "2025-06-01" }, "conformance": "backwards-compatible", "parsed-comparison": [ { "parent-path": "/", "identifier": "my-string", "stmt-type": "typedef", "changed": [ { "stmt": "length", "parent-stmt": "typedef", "change": "modified", Vaško, et al. Expires 25 April 2027 [Page 80] Internet-Draft YANG Schema Comparison October 2026 "conformance": "backwards-compatible" } ], "old": { "type": { "name": "string", "length": { "restriction": "1..10" } } }, "new": { "type": { "name": "string", "length": { "restriction": "1..20" } } } } ], "node-comparison": [ { "node": "/mod2:cont/l", "node-type": "leaf", "changed": [ { "stmt": "length", "change": "modified", "conformance": "backwards-compatible" } ], "old": { "status": "current", "config": true, "mandatory": false, "type": { "base-type": "string", "length": { "interval": [ { "min": "1", "max": "10" } ] } } }, Vaško, et al. Expires 25 April 2027 [Page 81] Internet-Draft YANG Schema Comparison October 2026 "new": { "status": "current", "config": true, "mandatory": false, "type": { "base-type": "string", "length": { "interval": [ { "min": "1", "max": "20" } ] } } } }, { "node": "/mod2:cont/l2", "node-type": "leaf", "changed": [ { "stmt": "node", "change": "added", "conformance": "backwards-compatible" } ], "new": { "status": "current", "config": true, "mandatory": false, "type": { "base-type": "int32" } } } ] } ] } } Authors' Addresses Michal Vaško (editor) CESNET Email: mvasko@cesnet.cz Vaško, et al. Expires 25 April 2027 [Page 82] Internet-Draft YANG Schema Comparison October 2026 Per Andersson Ionio Systems Email: per.ietf@ionio.se Robert Wilton Cisco Systems, Inc. Email: rwilton@cisco.com Vaško, et al. Expires 25 April 2027 [Page 83]