module ietf-module-tags {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-module-tags";
  prefix tags;

  import ietf-yang-types {
    prefix yang;
  }

  organization
    "IETF NetMod Working Group (NetMod)";
  contact
    "WG Web:  <https://datatracker.ietf.org/wg/netmod/>
     WG List: <mailto:netmod@ietf.org>

     Author: Christian Hopps
             <mailto:chopps@chopps.org>

     Author: Lou Berger
             <mailto:lberger@labn.net>

     Author: Dean Bogdanovic
             <mailto:ivandean@gmail.com>";

  description
    "This module describes a mechanism associating tags with YANG
     modules.  Tags may be IANA assigned or privately defined.

     Copyright (c) 2021 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 8819
     (https://www.rfc-editor.org/info/rfc8819); 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.";

  revision 2021-01-04 {
    description
      "Initial revision.";
    reference
      "RFC 8819: YANG Module Tags";
  }

  typedef tag {
    type string {
      length "1..max";
      pattern '[\S ]+';
    }
    description
      "A tag is a type of 'string' value that does not include
       carriage return, newline, or tab characters.  It SHOULD begin
       with a registered prefix; however, tags without a registered
       prefix SHOULD NOT be treated as invalid.";
  }

  extension module-tag {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'.  This extension statement
       is used by module authors to indicate the tags that SHOULD be
       added automatically by the system.  As such, the origin of the
       value for the predefined tags should be set to 'system'
       [RFC8342].";
  }

  container module-tags {
    description
      "Contains the list of modules and their associated tags.";
    list module {
      key "name";
      description
        "A list of modules and their associated tags.";
      leaf name {
        type yang:yang-identifier;
        mandatory true;
        description
          "The YANG module name.";
      }
      leaf-list tag {
        type tag;
        description
          "Tags associated with the module.  See the IANA 'YANG
           Module Tag Prefixes' registry for reserved prefixes and
           the IANA 'IETF YANG Module Tags' registry for IETF tags.

           The 'operational' state [RFC8342] view of this list is
           constructed using the following steps:

           1) System tags (i.e., tags of 'system' origin) are added.
           2) User-configured tags (i.e., tags of 'intended' origin)
           are added.
           3) Any tag that is equal to a masked-tag is removed.";
      }
      leaf-list masked-tag {
        type tag;
        description
          "The list of tags that should not be associated with this
           module.  The user can remove (mask) tags from the
           operational state datastore [RFC8342] by adding them to
           this list.  It is not an error to add tags to this list
           that are not associated with the module, but they have no
           operational effect.";
      }
    }
  }
}