schema mount NEW initial schema mount code
diff --git a/models/ietf-yang-schema-mount@2019-01-14.yang b/models/ietf-yang-schema-mount@2019-01-14.yang
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+module ietf-yang-schema-mount {
+  yang-version 1.1;
+  namespace "urn:ietf:params:xml:ns:yang:ietf-yang-schema-mount";
+  prefix yangmnt;
+
+  import ietf-inet-types {
+    prefix inet;
+    reference
+      "RFC 6991: Common YANG Data Types";
+  }
+
+  import ietf-yang-types {
+    prefix yang;
+    reference
+      "RFC 6991: Common YANG Data Types";
+  }
+
+  organization
+    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";
+
+  contact
+    "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
+     WG List:  <mailto:netmod@ietf.org>
+
+     Editor:   Martin Bjorklund
+               <mailto:mbj@tail-f.com>
+
+     Editor:   Ladislav Lhotka
+               <mailto:lhotka@nic.cz>";
+
+  description
+    "This module defines a YANG extension statement that can be used
+     to incorporate data models defined in other YANG modules in a
+     module.  It also defines operational state data that specify the
+     overall structure of the data model.
+
+     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 8528;
+     see the RFC itself for full legal notices.";
+
+  revision 2019-01-14 {
+    description
+      "Initial revision.";
+    reference
+      "RFC 8528: YANG Schema Mount";
+  }
+
+  /*
+   * Extensions
+   */
+
+  extension mount-point {
+    argument label;
+    description
+      "The argument 'label' is a YANG identifier, i.e., it is of the
+       type 'yang:yang-identifier'.
+
+       The 'mount-point' statement MUST NOT be used in a YANG
+       version 1 module, neither explicitly nor via a 'uses'
+       statement.
+       The 'mount-point' statement MAY be present as a substatement
+       of 'container' and 'list' and MUST NOT be present elsewhere.
+       There MUST NOT be more than one 'mount-point' statement in a
+       given 'container' or 'list' statement.
+
+       If a mount point is defined within a grouping, its label is
+       bound to the module where the grouping is used.
+
+       A mount point defines a place in the node hierarchy where
+       other data models may be attached.  A server that implements a
+       module with a mount point populates the
+       '/schema-mounts/mount-point' list with detailed information on
+       which data models are mounted at each mount point.
+
+       Note that the 'mount-point' statement does not define a new
+       data node.";
+  }
+
+  /*
+   * State data nodes
+   */
+
+  container schema-mounts {
+    config false;
+    description
+      "Contains information about the structure of the overall
+       mounted data model implemented in the server.";
+    list namespace {
+      key "prefix";
+      description
+        "This list provides a mapping of namespace prefixes that are
+         used in XPath expressions of 'parent-reference' leafs to the
+         corresponding namespace URI references.";
+      leaf prefix {
+        type yang:yang-identifier;
+        description
+          "Namespace prefix.";
+      }
+      leaf uri {
+        type inet:uri;
+        description
+          "Namespace URI reference.";
+      }
+    }
+    list mount-point {
+      key "module label";
+
+      description
+        "Each entry of this list specifies a schema for a particular
+         mount point.
+
+         Each mount point MUST be defined using the 'mount-point'
+         extension in one of the modules listed in the server's
+         YANG library instance with conformance type 'implement'.";
+      leaf module {
+        type yang:yang-identifier;
+        description
+          "Name of a module containing the mount point.";
+      }
+      leaf label {
+        type yang:yang-identifier;
+        description
+          "Label of the mount point defined using the 'mount-point'
+           extension.";
+      }
+      leaf config {
+        type boolean;
+        default "true";
+        description
+          "If this leaf is set to 'false', then all data nodes in the
+           mounted schema are read-only ('config false'), regardless
+           of their 'config' property.";
+      }
+      choice schema-ref {
+        mandatory true;
+        description
+          "Alternatives for specifying the schema.";
+        container inline {
+          presence
+            "A complete self-contained schema is mounted at the
+             mount point.";
+          description
+            "This node indicates that the server has mounted at least
+             the module 'ietf-yang-library' at the mount point, and
+             its instantiation provides the information about the
+             mounted schema.
+
+             Different instances of the mount point may have
+             different schemas mounted.";
+        }
+        container shared-schema {
+          presence
+            "The mounted schema together with the 'parent-reference'
+             make up the schema for this mount point.";
+
+          description
+            "This node indicates that the server has mounted at least
+             the module 'ietf-yang-library' at the mount point, and
+             its instantiation provides the information about the
+             mounted schema.  When XPath expressions in the mounted
+             schema are evaluated, the 'parent-reference' leaf-list
+             is taken into account.
+
+             Different instances of the mount point MUST have the
+             same schema mounted.";
+          leaf-list parent-reference {
+            type yang:xpath1.0;
+            description
+              "Entries of this leaf-list are XPath 1.0 expressions
+               that are evaluated in the following context:
+
+               - The context node is the node in the parent data tree
+                 where the mount-point is defined.
+
+               - The accessible tree is the parent data tree
+                 *without* any nodes defined in modules that are
+                 mounted inside the parent schema.
+
+               - The context position and context size are both equal
+                 to 1.
+
+               - The set of variable bindings is empty.
+
+               - The function library is the core function library
+                 defined in the W3C XPath 1.0 document
+                 (http://www.w3.org/TR/1999/REC-xpath-19991116) and
+                 the functions defined in Section 10 of RFC 7950.
+
+               - The set of namespace declarations is defined by the
+                 'namespace' list under 'schema-mounts'.
+
+               Each XPath expression MUST evaluate to a node-set
+               (possibly empty).  For the purposes of evaluating
+               XPath expressions whose context nodes are defined in
+               the mounted schema, the union of all these node-sets
+               together with ancestor nodes are added to the
+               accessible data tree.
+
+               Note that in the case 'ietf-yang-schema-mount' is
+               itself mounted, a 'parent-reference' in the mounted
+               module may refer to nodes that were brought into the
+               accessible tree through a 'parent-reference' in the
+               parent schema.";
+          }
+        }
+      }
+    }
+  }
+}