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+Internet Engineering Task Force (IETF)                        A. Bierman
+Request for Comments: 8525                                     YumaWorks
+Obsoletes: 7895                                             M. Bjorklund
+Category: Standards Track                                 Tail-f Systems
+ISSN: 2070-1721                                         J. Schoenwaelder
+                                                       Jacobs University
+                                                               K. Watsen
+                                                         Watsen Networks
+                                                               R. Wilton
+                                                           Cisco Systems
+                                                              March 2019
+
+
+                              YANG Library
+
+Abstract
+
+   This document describes a YANG library that provides information
+   about the YANG modules, datastores, and datastore schemas used by a
+   network management server.  Simple caching mechanisms are provided to
+   allow clients to minimize retrieval of this information.  This
+   version of the YANG library supports the Network Management Datastore
+   Architecture (NMDA) by listing all datastores supported by a network
+   management server and the schema that is used by each of these
+   datastores.
+
+   This document obsoletes RFC 7895.
+
+Status of This Memo
+
+   This is an Internet Standards Track document.
+
+   This document is a product of the Internet Engineering Task Force
+   (IETF).  It represents the consensus of the IETF community.  It has
+   received public review and has been approved for publication by the
+   Internet Engineering Steering Group (IESG).  Further information on
+   Internet Standards is available in Section 2 of RFC 7841.
+
+   Information about the current status of this document, any errata,
+   and how to provide feedback on it may be obtained at
+   https://www.rfc-editor.org/info/rfc8525.
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 1]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+Copyright Notice
+
+   Copyright (c) 2019 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 and restrictions with respect
+   to this document.  Code Components extracted from this document must
+   include Simplified BSD License text as described in Section 4.e of
+   the Trust Legal Provisions and are provided without warranty as
+   described in the Simplified BSD License.
+
+Table of Contents
+
+   1. Introduction ....................................................3
+      1.1. Terminology ................................................4
+   2. Objectives ......................................................5
+   3. YANG Library Data Model .........................................6
+   4. YANG Library YANG Module ........................................8
+   5. IANA Considerations ............................................20
+   6. Security Considerations ........................................21
+   7. References .....................................................22
+      7.1. Normative References ......................................22
+      7.2. Informative References ....................................23
+   Appendix A.  Summary of Changes from RFC 7895 .....................25
+   Appendix B.  Example YANG Library Instance for a Basic Server .....25
+   Appendix C.  Example YANG Library Instance for an Advanced Server .27
+   Authors' Addresses ................................................32
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 2]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+1.  Introduction
+
+   There is a need for a standard mechanism to expose which YANG modules
+   [RFC7950], datastores [RFC8342], and datastore schemas [RFC8342] are
+   in use by a network management server.
+
+   This document defines the YANG module "ietf-yang-library" that
+   provides this information.  This version of the YANG library is
+   compatible with the Network Management Datastore Architecture (NMDA)
+   [RFC8342].  The previous version of the YANG library, defined in
+   [RFC7895], is not compatible with the NMDA since it assumes that all
+   datastores have exactly the same schema.  This is not necessarily
+   true in the NMDA since dynamic configuration datastores may have
+   their own datastore schema.  Furthermore, the operational state
+   datastore may support non-configurable YANG modules in addition to
+   the YANG modules supported by conventional configuration datastores.
+
+   The old YANG library definitions have been retained (for backwards-
+   compatibility reasons), but the definitions have been marked as
+   deprecated.  For backwards compatibility, an NMDA-supporting server
+   SHOULD populate the deprecated "/modules-state" tree in a backwards-
+   compatible manner.  The new "/yang-library" tree will be ignored by
+   legacy clients but will provide all the data needed for NMDA-aware
+   clients (which will ignore the "/modules-state" tree).  The
+   recommended approach to populate "/modules-state" is to report the
+   YANG modules with "config true" data nodes that are configurable via
+   conventional configuration datastores and the YANG modules with
+   "config false" data nodes that are returned via a Network
+   Configuration Protocol (NETCONF) <get> operation or equivalent.
+
+   The YANG library information can be different on every server, and it
+   can change at runtime or across a server reboot.  If a server
+   implements multiple network management protocols to access the
+   server's datastores, then each such protocol may have its own
+   conceptual instantiation of the YANG library.
+
+   If a large number of YANG modules are utilized by a server, then the
+   YANG library contents can be relatively large.  Since the YANG
+   library contents change very infrequently, it is important that
+   clients be able to cache the YANG library contents and easily
+   identify whether their cache is out of date.
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 3]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+1.1.  Terminology
+
+   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.
+
+   The following terms are defined in [RFC7950]:
+
+   o  module
+
+   o  submodule
+
+   o  data node
+
+   This document uses the phrase "implement a module" as defined in
+   Section 5.6.5 of [RFC7950].
+
+   The following terms are defined in [RFC8342]:
+
+   o  datastore
+
+   o  datastore schema
+
+   o  configuration
+
+   o  conventional configuration datastore
+
+   o  operational state
+
+   o  operational state datastore
+
+   o  dynamic configuration datastore
+
+   o  client
+
+   o  server
+
+   The following terms are used within this document:
+
+   o  YANG library: A collection of YANG modules, submodules,
+      datastores, and datastore schemas used by a server.
+
+   o  YANG library content identifier: A server-generated identifier of
+      the contents of the YANG library.
+
+   Tree diagrams in this document use the notation defined in [RFC8340].
+
+
+
+Bierman, et al.              Standards Track                    [Page 4]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+2.  Objectives
+
+   The following information is needed by a client application (for each
+   YANG module in the library) to fully utilize the YANG data modeling
+   language:
+
+   o  name: The name of the YANG module.
+
+   o  revision: If defined in the YANG module or submodule, the revision
+      is derived from the most recent revision statement within the
+      module or submodule.
+
+   o  submodule list: The name and (if defined) revision of each
+      submodule used by the module must be identified.
+
+   o  feature list: The name of each YANG feature supported by the
+      server must be identified.
+
+   o  deviation list: The name of each YANG module with deviation
+      statements affecting a given YANG module must be identified.
+
+   In addition, the following information is needed by a client
+   application for each datastore supported by a server:
+
+   o  identity: The YANG identity for the datastore.
+
+   o  schema: The schema (i.e., the set of modules) implemented by the
+      datastore.
+
+   In order to select one out of several possible designs for the YANG
+   library data model, the following criteria were used:
+
+   1.  The information must be efficient for a client to consume.  Since
+       the size of the YANG library can be quite large, it should be
+       possible for clients to cache the YANG library information.
+
+   2.  A dynamic configuration datastore must be able to implement a
+       module or feature that is not implemented in the conventional
+       configuration datastores.
+
+   3.  It must be possible to not implement a module or feature in
+       <operational>, even if it is implemented in some other datastore.
+       This is required for transition purposes; a server that wants to
+       implement <operational> should not have to implement all modules
+       at once.
+
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 5]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   4.  A given module can only be implemented in one revision in all
+       datastores.  If a module is implemented in more than one
+       datastore, the same revision is implemented in all these
+       datastores.
+
+   5.  Multiple revisions can be used for import, if import-by revision
+       is used.
+
+   6.  It must be possible to use the YANG library by schema mount
+       [RFC8528].
+
+3.  YANG Library Data Model
+
+   The "ietf-yang-library" YANG module provides information about the
+   modules, submodules, datastores, and datastore schemas supported by a
+   server.  All data nodes in the "ietf-yang-library" module are "config
+   false" and thus only accessible in the operational state datastore.
+
+   +-----------+
+   | datastore |
+   +-----------+
+        |
+        | has a
+        V
+   +-----------+            +--------+                +------------+
+   | datastore |  union of  | module |  consists of   | modules +  |
+   |  schema   |----------->|  set   |--------------->| submodules |
+   +-----------+            +--------+                +------------+
+
+                                 Figure 1
+
+   The conceptual model of the YANG library is depicted in Figure 1.
+   Following the NMDA, every datastore has an associated datastore
+   schema.  A datastore schema is a union of module sets, and every
+   module set is a collection of modules and submodules, including the
+   modules and submodules used for imports.  Note that multiple
+   datastores may refer to the same datastore schema.  Furthermore, it
+   is possible for individual datastore schemas to share module sets.  A
+   common use case is the operational state datastore schema, which is a
+   superset of the schema used by conventional configuration datastores.
+
+   Below is the YANG tree diagram for the "ietf-yang-library" module,
+   excluding the deprecated "/modules-state" tree:
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 6]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   module: ietf-yang-library
+     +--ro yang-library
+        +--ro module-set* [name]
+        |  +--ro name                  string
+        |  +--ro module* [name]
+        |  |  +--ro name         yang:yang-identifier
+        |  |  +--ro revision?    revision-identifier
+        |  |  +--ro namespace    inet:uri
+        |  |  +--ro location*    inet:uri
+        |  |  +--ro submodule* [name]
+        |  |  |  +--ro name        yang:yang-identifier
+        |  |  |  +--ro revision?   revision-identifier
+        |  |  |  +--ro location*   inet:uri
+        |  |  +--ro feature*     yang:yang-identifier
+        |  |  +--ro deviation*   -> ../../module/name
+        |  +--ro import-only-module* [name revision]
+        |     +--ro name         yang:yang-identifier
+        |     +--ro revision     union
+        |     +--ro namespace    inet:uri
+        |     +--ro location*    inet:uri
+        |     +--ro submodule* [name]
+        |        +--ro name        yang:yang-identifier
+        |        +--ro revision?   revision-identifier
+        |        +--ro location*   inet:uri
+        +--ro schema* [name]
+        |  +--ro name          string
+        |  +--ro module-set*   -> ../../module-set/name
+        +--ro datastore* [name]
+        |  +--ro name      ds:datastore-ref
+        |  +--ro schema    -> ../../schema/name
+        +--ro content-id    string
+
+     notifications:
+       +---n yang-library-update
+          +--ro content-id    -> /yang-library/content-id
+
+   The "/yang-library" container holds the entire YANG library.  The
+   container has the following child nodes:
+
+   o  The "/yang-library/module-set" contains entries representing
+      module sets.  The list "/yang-library/module-set/module"
+      enumerates the modules that belong to the module set.  A module is
+      listed together with its submodules (if any), a set of features,
+      and any deviation modules.  The list "/yang-library/module-set/
+      import-only-module" lists all modules (and their submodules) used
+      only for imports.  The assignment of a module to a module set is
+
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 7]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+      at the server's discretion.  This revision of the YANG library
+      attaches no semantics as to which module set a module is listed
+      in.
+
+   o  The "/yang-library/schema" list contains an entry for each
+      datastore schema supported by the server.  All conventional
+      configuration datastores use the same "schema" list entry.  A
+      dynamic configuration datastore may use a different datastore
+      schema from the conventional configuration datastores and hence
+      may require a separate "schema" entry.  A "schema" entry has a
+      leaf-list of references to entries in the "module-set" list.  The
+      schema consists of the union of all modules in all referenced
+      module sets.
+
+   o  The "/yang-library/datastore" list contains one entry for each
+      datastore supported by the server, and it identifies the datastore
+      schema associated with a datastore via a reference to an entry in
+      the "schema" list.  Each supported conventional configuration
+      datastore has a separate entry, pointing to the same "schema" list
+      element.
+
+   o  The "/yang-library/content-id" leaf contains the YANG library
+      content identifier, which is an implementation-specific identifier
+      representing the current information in the YANG library on a
+      specific server.  The value of this leaf MUST change whenever the
+      information in the YANG library changes.  There is no requirement
+      that the same information always result in the same "content-id"
+      value.  This leaf allows a client to fetch all schema information
+      once, cache it, and only refetch it if the value of this leaf has
+      been changed.  If the value of this leaf changes, the server also
+      generates a "yang-library-update" notification.
+
+   Note that for a NETCONF server implementing the NETCONF extensions to
+   support the NMDA [RFC8526], a change of the YANG library content
+   identifier results in a new value for the :yang-library:1.1
+   capability defined in [RFC8526].  Thus, if such a server implements
+   NETCONF notifications [RFC5277] and the "netconf-capability-change"
+   notification [RFC6470], a "netconf-capability-change" notification is
+   generated whenever the YANG library content identifier changes.
+
+4.  YANG Library YANG Module
+
+   The "ietf-yang-library" YANG module imports definitions from the
+   "ietf-yang-types" and "ietf-inet-types" modules defined in [RFC6991]
+   and from the "ietf-datastores" module defined in [RFC8342].  While
+   the YANG module is defined using YANG version 1.1, the YANG library
+   supports YANG modules written in any version of YANG.
+
+
+
+
+Bierman, et al.              Standards Track                    [Page 8]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   <CODE BEGINS> file "ietf-yang-library@2019-01-04.yang"
+
+   module ietf-yang-library {
+     yang-version 1.1;
+     namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library";
+     prefix yanglib;
+
+     import ietf-yang-types {
+       prefix yang;
+       reference
+         "RFC 6991: Common YANG Data Types";
+     }
+     import ietf-inet-types {
+       prefix inet;
+       reference
+         "RFC 6991: Common YANG Data Types";
+     }
+     import ietf-datastores {
+       prefix ds;
+       reference
+         "RFC 8342: Network Management Datastore Architecture
+                    (NMDA)";
+     }
+
+     organization
+       "IETF NETCONF (Network Configuration) Working Group";
+     contact
+       "WG Web:   <https://datatracker.ietf.org/wg/netconf/>
+        WG List:  <mailto:netconf@ietf.org>
+
+        Author:   Andy Bierman
+                  <mailto:andy@yumaworks.com>
+
+        Author:   Martin Bjorklund
+                  <mailto:mbj@tail-f.com>
+
+        Author:   Juergen Schoenwaelder
+                  <mailto:j.schoenwaelder@jacobs-university.de>
+
+        Author:   Kent Watsen
+                  <mailto:kent+ietf@watsen.net>
+
+        Author:   Robert Wilton
+                  <mailto:rwilton@cisco.com>";
+     description
+       "This module provides information about the YANG modules,
+        datastores, and datastore schemas used by a network
+        management server.
+
+
+
+Bierman, et al.              Standards Track                    [Page 9]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+        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.
+
+        Copyright (c) 2019 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 Simplified 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 8525; see
+        the RFC itself for full legal notices.";
+
+     revision 2019-01-04 {
+       description
+         "Added support for multiple datastores according to the
+          Network Management Datastore Architecture (NMDA).";
+       reference
+         "RFC 8525: YANG Library";
+     }
+     revision 2016-04-09 {
+       description
+         "Initial revision.";
+       reference
+         "RFC 7895: YANG Module Library";
+     }
+
+     /*
+      * Typedefs
+      */
+
+     typedef revision-identifier {
+       type string {
+         pattern '\d{4}-\d{2}-\d{2}';
+       }
+       description
+         "Represents a specific date in YYYY-MM-DD format.";
+     }
+
+     /*
+      * Groupings
+      */
+
+
+
+Bierman, et al.              Standards Track                   [Page 10]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+     grouping module-identification-leafs {
+       description
+         "Parameters for identifying YANG modules and submodules.";
+       leaf name {
+         type yang:yang-identifier;
+         mandatory true;
+         description
+           "The YANG module or submodule name.";
+       }
+       leaf revision {
+         type revision-identifier;
+         description
+           "The YANG module or submodule revision date.  If no revision
+            statement is present in the YANG module or submodule, this
+            leaf is not instantiated.";
+       }
+     }
+
+     grouping location-leaf-list {
+       description
+         "Common leaf-list parameter for the locations of modules and
+          submodules.";
+       leaf-list location {
+         type inet:uri;
+         description
+           "Contains a URL that represents the YANG schema
+            resource for this module or submodule.
+
+            This leaf will only be present if there is a URL
+            available for retrieval of the schema for this entry.";
+       }
+     }
+
+     grouping module-implementation-parameters {
+       description
+         "Parameters for describing the implementation of a module.";
+       leaf-list feature {
+         type yang:yang-identifier;
+         description
+           "List of all YANG feature names from this module that are
+            supported by the server, regardless whether they are defined
+            in the module or any included submodule.";
+       }
+       leaf-list deviation {
+         type leafref {
+           path "../../module/name";
+         }
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 11]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+         description
+           "List of all YANG deviation modules used by this server to
+            modify the conformance of the module associated with this
+            entry.  Note that the same module can be used for deviations
+            for multiple modules, so the same entry MAY appear within
+            multiple 'module' entries.
+
+            This reference MUST NOT (directly or indirectly)
+            refer to the module being deviated.
+
+            Robust clients may want to make sure that they handle a
+            situation where a module deviates itself (directly or
+            indirectly) gracefully.";
+       }
+     }
+
+     grouping module-set-parameters {
+       description
+         "A set of parameters that describe a module set.";
+       leaf name {
+         type string;
+         description
+           "An arbitrary name of the module set.";
+       }
+       list module {
+         key "name";
+         description
+           "An entry in this list represents a module implemented by the
+            server, as per Section 5.6.5 of RFC 7950, with a particular
+            set of supported features and deviations.";
+         reference
+           "RFC 7950: The YANG 1.1 Data Modeling Language";
+         uses module-identification-leafs;
+         leaf namespace {
+           type inet:uri;
+           mandatory true;
+           description
+             "The XML namespace identifier for this module.";
+         }
+         uses location-leaf-list;
+         list submodule {
+           key "name";
+           description
+             "Each entry represents one submodule within the
+              parent module.";
+           uses module-identification-leafs;
+           uses location-leaf-list;
+         }
+
+
+
+Bierman, et al.              Standards Track                   [Page 12]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+         uses module-implementation-parameters;
+       }
+       list import-only-module {
+         key "name revision";
+         description
+           "An entry in this list indicates that the server imports
+            reusable definitions from the specified revision of the
+            module but does not implement any protocol-accessible
+            objects from this revision.
+
+            Multiple entries for the same module name MAY exist.  This
+            can occur if multiple modules import the same module but
+            specify different revision dates in the import statements.";
+         leaf name {
+           type yang:yang-identifier;
+           description
+             "The YANG module name.";
+         }
+         leaf revision {
+           type union {
+             type revision-identifier;
+             type string {
+               length "0";
+             }
+           }
+           description
+             "The YANG module revision date.
+              A zero-length string is used if no revision statement
+              is present in the YANG module.";
+         }
+         leaf namespace {
+           type inet:uri;
+           mandatory true;
+           description
+             "The XML namespace identifier for this module.";
+         }
+         uses location-leaf-list;
+         list submodule {
+           key "name";
+           description
+             "Each entry represents one submodule within the
+              parent module.";
+           uses module-identification-leafs;
+           uses location-leaf-list;
+         }
+       }
+     }
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 13]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+     grouping yang-library-parameters {
+       description
+         "The YANG library data structure is represented as a grouping
+          so it can be reused in configuration or another monitoring
+          data structure.";
+       list module-set {
+         key "name";
+         description
+           "A set of modules that may be used by one or more schemas.
+
+            A module set does not have to be referentially complete,
+            i.e., it may define modules that contain import statements
+            for other modules not included in the module set.";
+         uses module-set-parameters;
+       }
+       list schema {
+         key "name";
+         description
+           "A datastore schema that may be used by one or more
+            datastores.
+
+            The schema must be valid and referentially complete, i.e.,
+            it must contain modules to satisfy all used import
+            statements for all modules specified in the schema.";
+         leaf name {
+           type string;
+           description
+             "An arbitrary name of the schema.";
+         }
+         leaf-list module-set {
+           type leafref {
+             path "../../module-set/name";
+           }
+           description
+             "A set of module-sets that are included in this schema.
+              If a non-import-only module appears in multiple module
+              sets, then the module revision and the associated features
+              and deviations must be identical.";
+         }
+       }
+       list datastore {
+         key "name";
+         description
+           "A datastore supported by this server.
+
+            Each datastore indicates which schema it supports.
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 14]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+            The server MUST instantiate one entry in this list per
+            specific datastore it supports.
+            Each datastore entry with the same datastore schema SHOULD
+            reference the same schema.";
+         leaf name {
+           type ds:datastore-ref;
+           description
+             "The identity of the datastore.";
+         }
+         leaf schema {
+           type leafref {
+             path "../../schema/name";
+           }
+           mandatory true;
+           description
+             "A reference to the schema supported by this datastore.
+              All non-import-only modules of the schema are implemented
+              with their associated features and deviations.";
+         }
+       }
+     }
+
+     /*
+      * Top-level container
+      */
+
+     container yang-library {
+       config false;
+       description
+         "Container holding the entire YANG library of this server.";
+       uses yang-library-parameters;
+       leaf content-id {
+         type string;
+         mandatory true;
+         description
+           "A server-generated identifier of the contents of the
+            '/yang-library' tree.  The server MUST change the value of
+            this leaf if the information represented by the
+            '/yang-library' tree, except '/yang-library/content-id', has
+            changed.";
+       }
+     }
+
+     /*
+      * Notifications
+      */
+
+     notification yang-library-update {
+
+
+
+Bierman, et al.              Standards Track                   [Page 15]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       description
+         "Generated when any YANG library information on the
+          server has changed.";
+       leaf content-id {
+         type leafref {
+           path "/yanglib:yang-library/yanglib:content-id";
+         }
+         mandatory true;
+         description
+           "Contains the YANG library content identifier for the updated
+            YANG library at the time the notification is generated.";
+       }
+     }
+
+     /*
+      * Legacy groupings
+      */
+
+     grouping module-list {
+       status deprecated;
+       description
+         "The module data structure is represented as a grouping
+          so it can be reused in configuration or another monitoring
+          data structure.";
+
+       grouping common-leafs {
+         status deprecated;
+         description
+           "Common parameters for YANG modules and submodules.";
+         leaf name {
+           type yang:yang-identifier;
+           status deprecated;
+           description
+             "The YANG module or submodule name.";
+         }
+         leaf revision {
+           type union {
+             type revision-identifier;
+             type string {
+               length "0";
+             }
+           }
+           status deprecated;
+           description
+             "The YANG module or submodule revision date.
+              A zero-length string is used if no revision statement
+              is present in the YANG module or submodule.";
+         }
+
+
+
+Bierman, et al.              Standards Track                   [Page 16]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       }
+
+       grouping schema-leaf {
+         status deprecated;
+         description
+           "Common schema leaf parameter for modules and submodules.";
+         leaf schema {
+           type inet:uri;
+           description
+             "Contains a URL that represents the YANG schema
+              resource for this module or submodule.
+
+              This leaf will only be present if there is a URL
+              available for retrieval of the schema for this entry.";
+         }
+       }
+       list module {
+         key "name revision";
+         status deprecated;
+         description
+           "Each entry represents one revision of one module
+            currently supported by the server.";
+         uses common-leafs {
+           status deprecated;
+         }
+         uses schema-leaf {
+           status deprecated;
+         }
+         leaf namespace {
+           type inet:uri;
+           mandatory true;
+           status deprecated;
+           description
+             "The XML namespace identifier for this module.";
+         }
+         leaf-list feature {
+           type yang:yang-identifier;
+           status deprecated;
+           description
+             "List of YANG feature names from this module that are
+              supported by the server, regardless of whether they are
+              defined in the module or any included submodule.";
+         }
+         list deviation {
+           key "name revision";
+           status deprecated;
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 17]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+           description
+             "List of YANG deviation module names and revisions
+              used by this server to modify the conformance of
+              the module associated with this entry.  Note that
+              the same module can be used for deviations for
+              multiple modules, so the same entry MAY appear
+              within multiple 'module' entries.
+
+              The deviation module MUST be present in the 'module'
+              list, with the same name and revision values.
+              The 'conformance-type' value will be 'implement' for
+              the deviation module.";
+           uses common-leafs {
+             status deprecated;
+           }
+         }
+         leaf conformance-type {
+           type enumeration {
+             enum implement {
+               description
+                 "Indicates that the server implements one or more
+                  protocol-accessible objects defined in the YANG module
+                  identified in this entry.  This includes deviation
+                  statements defined in the module.
+
+                  For YANG version 1.1 modules, there is at most one
+                  'module' entry with conformance type 'implement' for a
+                  particular module name, since YANG 1.1 requires that
+                  at most one revision of a module is implemented.
+
+                  For YANG version 1 modules, there SHOULD NOT be more
+                  than one 'module' entry for a particular module
+                  name.";
+             }
+             enum import {
+               description
+                 "Indicates that the server imports reusable definitions
+                  from the specified revision of the module but does
+                  not implement any protocol-accessible objects from
+                  this revision.
+
+                  Multiple 'module' entries for the same module name MAY
+                  exist.  This can occur if multiple modules import the
+                  same module but specify different revision dates in
+                  the import statements.";
+             }
+           }
+           mandatory true;
+
+
+
+Bierman, et al.              Standards Track                   [Page 18]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+           status deprecated;
+           description
+             "Indicates the type of conformance the server is claiming
+              for the YANG module identified by this entry.";
+         }
+         list submodule {
+           key "name revision";
+           status deprecated;
+           description
+             "Each entry represents one submodule within the
+              parent module.";
+           uses common-leafs {
+             status deprecated;
+           }
+           uses schema-leaf {
+             status deprecated;
+           }
+         }
+       }
+     }
+
+     /*
+      * Legacy operational state data nodes
+      */
+
+     container modules-state {
+       config false;
+       status deprecated;
+       description
+         "Contains YANG module monitoring information.";
+       leaf module-set-id {
+         type string;
+         mandatory true;
+         status deprecated;
+         description
+           "Contains a server-specific identifier representing
+            the current set of modules and submodules.  The
+            server MUST change the value of this leaf if the
+            information represented by the 'module' list instances
+            has changed.";
+       }
+       uses module-list {
+         status deprecated;
+       }
+     }
+
+     /*
+      * Legacy notifications
+
+
+
+Bierman, et al.              Standards Track                   [Page 19]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+      */
+
+     notification yang-library-change {
+       status deprecated;
+       description
+         "Generated when the set of modules and submodules supported
+          by the server has changed.";
+       leaf module-set-id {
+         type leafref {
+           path "/yanglib:modules-state/yanglib:module-set-id";
+         }
+         mandatory true;
+         status deprecated;
+         description
+           "Contains the module-set-id value representing the
+            set of modules and submodules supported at the server
+            at the time the notification is generated.";
+       }
+     }
+   }
+
+
+   <CODE ENDS>
+
+5.  IANA Considerations
+
+   RFC 7895 previously registered one URI in the "IETF XML Registry"
+   [RFC3688].  This document takes over this registration entry made by
+   RFC 7895 and changes the Registrant Contact to the IESG according to
+   Section 4 of [RFC3688].
+
+     URI: urn:ietf:params:xml:ns:yang:ietf-yang-library
+
+     Registrant Contact: The IESG.
+
+     XML: N/A, the requested URI is an XML namespace.
+
+   This document registers a YANG module in the "YANG Module Names"
+   registry [RFC6020]:
+
+     name:         ietf-yang-library
+     namespace:    urn:ietf:params:xml:ns:yang:ietf-yang-library
+     prefix:       yanglib
+     reference:    RFC 8525
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 20]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+6.  Security Considerations
+
+   The YANG module specified in this document defines a schema for data
+   that is designed to 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.
+
+   Some of the readable data nodes in this YANG module may be considered
+   sensitive or vulnerable in some network environments.  It is thus
+   important to control read access (e.g., via get, get-config, or
+   notification) to these data nodes.  These are the subtrees and data
+   nodes and their sensitivity/vulnerability:
+
+   The "/yang-library" subtree of the YANG library may help an attacker
+   identify the server capabilities and server implementations with
+   known bugs since the set of YANG modules supported by a server may
+   reveal the kind of device and the manufacturer of the device.
+   Although some of this information may be available to all NETCONF
+   users via the NETCONF <hello> message (or similar messages in other
+   management protocols), this YANG module potentially exposes
+   additional details that could be of some assistance to an attacker.
+   Server vulnerabilities may be specific to particular modules, module
+   revisions, module features, or even module deviations.  For example,
+   if a particular operation on a particular data node is known to cause
+   a server to crash or significantly degrade device performance, then
+   the "module" list information will help an attacker identify server
+   implementations with such a defect, in order to launch a denial-of-
+   service attack on the device.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 21]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+7.  References
+
+7.1.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119,
+              DOI 10.17487/RFC2119, March 1997,
+              <https://www.rfc-editor.org/info/rfc2119>.
+
+   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
+              DOI 10.17487/RFC3688, January 2004,
+              <https://www.rfc-editor.org/info/rfc3688>.
+
+   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
+              the Network Configuration Protocol (NETCONF)", RFC 6020,
+              DOI 10.17487/RFC6020, October 2010,
+              <https://www.rfc-editor.org/info/rfc6020>.
+
+   [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,
+              <https://www.rfc-editor.org/info/rfc6241>.
+
+   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
+              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
+              <https://www.rfc-editor.org/info/rfc6242>.
+
+   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
+              RFC 6991, DOI 10.17487/RFC6991, July 2013,
+              <https://www.rfc-editor.org/info/rfc6991>.
+
+   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
+              RFC 7950, DOI 10.17487/RFC7950, August 2016,
+              <https://www.rfc-editor.org/info/rfc7950>.
+
+   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
+              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
+              <https://www.rfc-editor.org/info/rfc8040>.
+
+   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
+              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
+              May 2017, <https://www.rfc-editor.org/info/rfc8174>.
+
+   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
+              Access Control Model", STD 91, RFC 8341,
+              DOI 10.17487/RFC8341, March 2018,
+              <https://www.rfc-editor.org/info/rfc8341>.
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 22]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
+              and R. Wilton, "Network Management Datastore Architecture
+              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
+              <https://www.rfc-editor.org/info/rfc8342>.
+
+   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
+              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
+              <https://www.rfc-editor.org/info/rfc8446>.
+
+7.2.  Informative References
+
+   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
+              Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
+              <https://www.rfc-editor.org/info/rfc5277>.
+
+   [RFC6470]  Bierman, A., "Network Configuration Protocol (NETCONF)
+              Base Notifications", RFC 6470, DOI 10.17487/RFC6470,
+              February 2012, <https://www.rfc-editor.org/info/rfc6470>.
+
+   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
+              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
+              <https://www.rfc-editor.org/info/rfc7895>.
+
+   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
+              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
+              <https://www.rfc-editor.org/info/rfc8340>.
+
+   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
+              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
+              <https://www.rfc-editor.org/info/rfc8343>.
+
+   [RFC8344]  Bjorklund, M., "A YANG Data Model for IP Management",
+              RFC 8344, DOI 10.17487/RFC8344, March 2018,
+              <https://www.rfc-editor.org/info/rfc8344>.
+
+   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
+              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
+              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
+              2018, <https://www.rfc-editor.org/info/rfc8345>.
+
+   [RFC8348]  Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
+              YANG Data Model for Hardware Management", RFC 8348,
+              DOI 10.17487/RFC8348, March 2018,
+              <https://www.rfc-editor.org/info/rfc8348>.
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 23]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
+              Routing Management (NMDA Version)", RFC 8349,
+              DOI 10.17487/RFC8349, March 2018,
+              <https://www.rfc-editor.org/info/rfc8349>.
+
+   [RFC8526]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
+              and R. Wilton, "NETCONF Extensions to Support the Network
+              Management Datastore Architecture", RFC 8526,
+              DOI 10.17487/RFC8526, March 2019,
+              <https://www.rfc-editor.org/info/rfc8526>.
+
+   [RFC8528]  Bjorklund, M. and L. Lhotka, "YANG Schema Mount",
+              RFC 8528, DOI 10.17487/RFC8528, March 2019,
+              <https://www.rfc-editor.org/info/rfc8528>.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 24]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+Appendix A.  Summary of Changes from RFC 7895
+
+   This document changes [RFC7895] in the following ways:
+
+   o  Renamed document title from "YANG Module Library" to "YANG
+      Library".
+
+   o  Added a new top-level "/yang-library" container to hold the entire
+      YANG library providing information about module sets, schemas, and
+      datastores.
+
+   o  Refactored the "/modules-state" container into a new
+      "/yang-library/module-set" list.
+
+   o  Added a new "/yang-library/schema" list and a new "/yang-library/
+      datastore" list.
+
+   o  Added a set of new groupings as replacements for the deprecated
+      groupings.
+
+   o  Added a "yang-library-update" notification as a replacement for
+      the deprecated "yang-library-change" notification.
+
+   o  Deprecated the "/modules-state" tree.
+
+   o  Deprecated the "/module-list" grouping.
+
+   o  Deprecated the "/yang-library-change" notification.
+
+Appendix B.  Example YANG Library Instance for a Basic Server
+
+   The following example shows the YANG library of a basic server
+   implementing the "ietf-interfaces" [RFC8343] and "ietf-ip" [RFC8344]
+   modules in the <running>, <startup>, and <operational> datastores and
+   the "ietf-hardware" [RFC8348] module in the <operational> datastore.
+
+   Newline characters in leaf values are added for formatting reasons.
+
+   <yang-library
+       xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
+       xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
+
+     <module-set>
+       <name>config-modules</name>
+       <module>
+         <name>ietf-interfaces</name>
+         <revision>2018-02-20</revision>
+         <namespace>
+
+
+
+Bierman, et al.              Standards Track                   [Page 25]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+           urn:ietf:params:xml:ns:yang:ietf-interfaces
+         </namespace>
+       </module>
+       <module>
+         <name>ietf-ip</name>
+         <revision>2018-02-22</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-ip
+         </namespace>
+       </module>
+       <import-only-module>
+         <name>ietf-yang-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-yang-types
+         </namespace>
+       </import-only-module>
+       <import-only-module>
+         <name>ietf-inet-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-inet-types
+         </namespace>
+       </import-only-module>
+     </module-set>
+
+     <module-set>
+       <name>state-modules</name>
+       <module>
+         <name>ietf-hardware</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-hardware
+         </namespace>
+       </module>
+       <import-only-module>
+         <name>ietf-inet-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-inet-types
+         </namespace>
+       </import-only-module>
+       <import-only-module>
+         <name>ietf-yang-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-yang-types
+         </namespace>
+
+
+
+Bierman, et al.              Standards Track                   [Page 26]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       </import-only-module>
+       <import-only-module>
+         <name>iana-hardware</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:iana-hardware
+         </namespace>
+       </import-only-module>
+     </module-set>
+
+     <schema>
+       <name>config-schema</name>
+       <module-set>config-modules</module-set>
+     </schema>
+     <schema>
+       <name>state-schema</name>
+       <module-set>config-modules</module-set>
+       <module-set>state-modules</module-set>
+     </schema>
+
+     <datastore>
+       <name>ds:startup</name>
+       <schema>config-schema</schema>
+     </datastore>
+     <datastore>
+       <name>ds:running</name>
+       <schema>config-schema</schema>
+     </datastore>
+     <datastore>
+       <name>ds:operational</name>
+       <schema>state-schema</schema>
+     </datastore>
+
+     <content-id>75a43df9bd56b92aacc156a2958fbe12312fb285</content-id>
+   </yang-library>
+
+Appendix C.  Example YANG Library Instance for an Advanced Server
+
+   The following example extends the example in Appendix B by using
+   modules from [RFC8345] and [RFC8349] to illustrate a slightly more
+   advanced server that:
+
+   o  Has a module with features only enabled in <operational>; the
+      "ietf-routing" module is supported in <running>, <startup>, and
+      <operational>, but the "multiple-ribs" and "router-id" features
+      are only enabled in <operational>.  Hence, the "router-id" leaf
+      may be read but not configured.
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 27]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+   o  Supports a dynamic configuration datastore "example-ds-ephemeral",
+      with only the "ietf-network" and "ietf-network-topology" modules
+      configurable via a notional dynamic configuration protocol.
+
+   o  Shows an example of datastore-specific deviations.  The
+      "example-vendor-hardware-deviations" module is included in the
+      schema for <operational> to remove data nodes that cannot be
+      supported by the server.
+
+   o  Shows how module-sets can be used to organize related modules
+      together.
+
+   Newline characters in leaf values are added for formatting reasons.
+
+   <yang-library
+       xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
+       xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"
+       xmlns:ex-ds-eph="urn:example:ds-ephemeral">
+
+     <module-set>
+       <name>config-state-modules</name>
+       <module>
+         <name>ietf-interfaces</name>
+         <revision>2018-02-20</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-interfaces
+         </namespace>
+       </module>
+       <module>
+         <name>ietf-ip</name>
+         <revision>2018-02-22</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-ip
+         </namespace>
+       </module>
+       <module>
+         <name>ietf-routing</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-routing
+         </namespace>
+       </module>
+       <import-only-module>
+         <name>ietf-yang-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-yang-types
+         </namespace>
+
+
+
+Bierman, et al.              Standards Track                   [Page 28]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       </import-only-module>
+       <import-only-module>
+         <name>ietf-inet-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-inet-types
+         </namespace>
+       </import-only-module>
+     </module-set>
+
+     <module-set>
+       <name>config-only-modules</name>
+       <module>
+         <name>ietf-routing</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-routing
+         </namespace>
+       </module>
+     </module-set>
+
+     <module-set>
+       <name>dynamic-config-state-modules</name>
+       <module>
+         <name>ietf-network</name>
+         <revision>2018-02-26</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-network
+         </namespace>
+       </module>
+       <module>
+         <name>ietf-network-topology</name>
+         <revision>2018-02-26</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-network-topology
+         </namespace>
+       </module>
+       <import-only-module>
+         <name>ietf-inet-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-inet-types
+         </namespace>
+       </import-only-module>
+     </module-set>
+
+     <module-set>
+       <name>state-only-modules</name>
+
+
+
+Bierman, et al.              Standards Track                   [Page 29]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       <module>
+         <name>ietf-hardware</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-hardware
+         </namespace>
+         <deviation>example-vendor-hardware-deviations</deviation>
+       </module>
+       <module>
+         <name>ietf-routing</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-routing
+         </namespace>
+         <feature>multiple-ribs</feature>
+         <feature>router-id</feature>
+       </module>
+       <module>
+         <name>example-vendor-hardware-deviations</name>
+         <revision>2018-01-31</revision>
+         <namespace>
+           urn:example:example-vendor-hardware-deviations
+         </namespace>
+       </module>
+       <import-only-module>
+         <name>ietf-inet-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-inet-types
+         </namespace>
+       </import-only-module>
+       <import-only-module>
+         <name>ietf-yang-types</name>
+         <revision>2013-07-15</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:ietf-yang-types
+         </namespace>
+       </import-only-module>
+       <import-only-module>
+         <name>iana-hardware</name>
+         <revision>2018-03-13</revision>
+         <namespace>
+           urn:ietf:params:xml:ns:yang:iana-hardware
+         </namespace>
+       </import-only-module>
+     </module-set>
+
+     <schema>
+
+
+
+Bierman, et al.              Standards Track                   [Page 30]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+       <name>config-schema</name>
+       <module-set>config-state-modules</module-set>
+       <module-set>config-only-modules</module-set>
+     </schema>
+     <schema>
+       <name>dynamic-config-schema</name>
+       <module-set>dynamic-config-state-modules</module-set>
+     </schema>
+     <schema>
+       <name>state-schema</name>
+       <module-set>config-state-modules</module-set>
+       <module-set>dynamic-config-state-modules</module-set>
+       <module-set>state-only-modules</module-set>
+     </schema>
+
+     <datastore>
+       <name>ds:startup</name>
+       <schema>config-schema</schema>
+     </datastore>
+     <datastore>
+       <name>ds:running</name>
+       <schema>config-schema</schema>
+     </datastore>
+     <datastore>
+       <name>ex-ds-eph:ds-ephemeral</name>
+       <schema>dynamic-config-schema</schema>
+     </datastore>
+     <datastore>
+       <name>ds:operational</name>
+       <schema>state-schema</schema>
+     </datastore>
+
+     <content-id>14782ab9bd56b92aacc156a2958fbe12312fb285</content-id>
+   </yang-library>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 31]
+
+RFC 8525                      YANG Library                    March 2019
+
+
+Authors' Addresses
+
+   Andy Bierman
+   YumaWorks
+
+   Email: andy@yumaworks.com
+
+
+   Martin Bjorklund
+   Tail-f Systems
+
+   Email: mbj@tail-f.com
+
+
+   Juergen Schoenwaelder
+   Jacobs University
+
+   Email: j.schoenwaelder@jacobs-university.de
+
+
+   Kent Watsen
+   Watsen Networks
+
+   Email: kent+ietf@watsen.net
+
+
+   Robert Wilton
+   Cisco Systems
+
+   Email: rwilton@cisco.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bierman, et al.              Standards Track                   [Page 32]
+