XML Encoding of Data Modeled with YANG

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 18 November 2024.¶

Copyright Notice

Copyright (c) 2024 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 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.¶

This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.¶

Table of Contents

4. Names and Namespaces

An XML element name is always identical to the identifier of the corresponding YANG data node.¶

All XML elements encoding YANG data are namespace qualified. The XML default namespace is never used in YANG encoded data.¶

The namespace of an XML element is either inherited from its ancestor or set using the "xmlns" attribute in the element.¶

The "xmlns" attribute may either set the XML default namespace or define and use a prefix for the namespace. For instance, the following two XML documents are the same.¶

Document 1:¶

<foo xmlns="https://example.com/foo"/>

Document 2:¶

<my-prefix:foo xmlns:my-prefix="https://example.com/foo"/>

The "namespace" statement of a module determines the namespace of all data node names defined in that module. If a data node is defined in a submodule, then the namespace of the main module is used.¶

A namespace MUST be set for all top-level XML elements and then also whenever the namespaces of the data node and its parent node are different.¶

For example, consider the following YANG module:¶

module example-foomod {

  namespace "https://example.com/foomod";

  prefix "foomod";

  container top {
    leaf foo {
      type uint8;
    }
  }
}

If the data model consists only of this module, then the following is valid XML-encoded configuration data:¶

<top xmlns="https://example.com/foomod">
  <foo>54</foo>
</top>

Note that the top-level element sets the default namespace which "foo" leaf inherits its parent container "top".¶

Now, assume that the container "top" is augmented from another module, "example-barmod":¶

module example-barmod {

  namespace "https://example.com/barmod";

  prefix "barmod";

  import example-foomod {
    prefix "foomod";
  }

  augment "/foomod:top" {
    leaf bar {
      type boolean;
    }
  }
}

Valid XML-encoded configuration data containing both leafs may then look like this:¶

<top xmlns="https://example.com/foomod">
  <foo>54</foo>
  <bar xmlns="https://example.com/barmod">true</bar>
</top>

The "bar" leaf's element sets a new default namespace because its parent is defined in a different module.¶

Prefixed namespace identifiers are sometimes needed when encoding values of the "identityref" and "instance-identifier" types. See Section 6.8 and Section 6.11 for details.¶

7. IANA Considerations

This document registers one capability identifier URN from the "Network Configuration Protocol (NETCONF) Capability URNs" registry:¶

Author's Address