[Docs] [txt|pdf|xml] [Tracker] [Email] [Nits]

Versions: 00

NETMOD Working Group                                           L. Lhotka
Internet-Draft                                                    CZ.NIC
Intended status: Standards Track                          March 09, 2017
Expires: September 10, 2017


                  Using Markup in YANG Text Arguments
                   draft-lhotka-netmod-yang-markup-00

Abstract

   This document defines a YANG extension that allows for specifying a
   media type for text in the arguments of these YANG statements:
   "contact", "description", "error-message", "organization" and
   "reference."

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 http://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 September 10, 2017.

Copyright Notice

   Copyright (c) 2017 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
   (http://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.




Lhotka                 Expires September 10, 2017               [Page 1]


Internet-Draft                 i-d-abbrev                     March 2017


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Declaring the Media Type of Text Arguments  . . . . . . . . .   3
   4.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Descriptions play an important role in YANG data models.  They may
   specify normative semantic constraints that cannot be expressed
   formally, instructions for implementors of the data model, and other
   vital information.  That is why descriptions often comprise several
   paragraphs of text and sometimes also other structures such all
   numbered or bulleted lists.

   So far, YANG modules have mostly used only plain text in the argument
   of the "description" statement, i.e., formatted text structures using
   just whitespace.  This is generally sufficient for human readers and
   also for including YANG modules in RFC documents, but less so for
   tools that are designed to process or use YANG modules in other ways,
   for example:

   o  converting YANG compact syntax to other formats (YIN, HTML)

   o  including YANG modules in standards and other documents whose
      source form in not plain text

   o  including description text in user interface elements.

   The above considerations also apply, albeit to a lesser extent, to
   other YANG statements with more structured arguments: "contact",
   "error-message", "organization" and "reference".

   In principle, it is possible to use any kind of markup such as
   markdown [RFC7764] but doing so would not be not very effective and
   tool-friendly unless the markup format is either standardized or
   declared in the module source.

   This document defines a YANG extension statement, "text-media-type",
   that can be placed as a substatement of the "module" or "submodule"
   statement to indicate the media type that is used throughout the



Lhotka                 Expires September 10, 2017               [Page 2]


Internet-Draft                 i-d-abbrev                     March 2017


   (sub)module for markup in the arguments of the five YANG statements
   mentioned above.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Declaring the Media Type of Text Arguments

   Section 4 below contains the "ietf-yang-text-media-type" module that
   defines a YANG language extension: "text-media-type".  Its purpose is
   to declare media type that is used for markup in the arguments of the
   following YANG statements:

   o  contact

   o  description

   o  error-message

   o  organization

   o  reference

   The common characteristic of these five statements is that their
   argument is represented as the <text> element in YIN format
   (Section 13 of [RFC7950]).

   The "text-media-type" extension is intended to be used at the top
   level of a YANG module or submodule, i.e., as a substatement of
   either "module" or "submodule" statement.  The declared media type
   applies to arguments of the above YANG statements throughout the
   module or submodule.

   The "text-media-type" extension MAY be ignored, and a module in which
   it appears MUST be valid YANG.

   The argument of the "text-media-type" extension is a string
   specifying the media type in the format defined in [RFC6838].  The
   media type SHOULD be registered by IANA in the "text" registry
   [IANA-MEDIA-TYPES].  Media type parameters MAY be used.

   It is RECOMMENDED to use only media types representing "lightweight"
   markup that is easy to read even in the unprocessed source form, such
   as "text/markdown".




Lhotka                 Expires September 10, 2017               [Page 3]


Internet-Draft                 i-d-abbrev                     March 2017


   YANG modules have to be use the UTF-8 character encoding, see
   Section 6 of [RFC7950].  This implies the following rules:

   o  Whenever the "charset" parameter is present, its value MUST be
      "UTF-8".

   o  If no default value is defined for the "charset" parameter of a
      given media type, or if a default value is defined but is
      different from "UTF-8", then the "charset" parameter MUST be
      present with the value of "UTF-8".

   Even if the "text-media-type" extension statement is present and
   markup used in text arguments, all YANG and YIN syntax rules still
   apply.

   The "ietf-yang-text-media-type" module not only defines but also uses
   the "text-media-type" extension statement, which illustrates its
   typical use.

4.  YANG Module

   RFC Editor: In this section, replace all occurrences of 'XXXX' with
   the actual RFC number and all occurrences of the revision date below
   with the date of RFC publication (and remove this note).

<CODE BEGINS> file "ietf-yang-text-media-type@2017-03-09.yang"

module ietf-yang-text-media-type {

  namespace "urn:ietf:params:xml:ns:yang:ietf-yang-text-media-type";

  prefix ymt;

  ymt:text-media-type "text/markdown; charset=UTF-8";

  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web:   <https://tools.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>

     WG Chair: Lou Berger
               <mailto:lberger@labn.net>

     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>




Lhotka                 Expires September 10, 2017               [Page 4]


Internet-Draft                 i-d-abbrev                     March 2017


     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>";

  description
    "This module defines the *text-media-type* extension that allows
     for specifying media-type for markup that is used in arguments
     of these YANG statements: contact, description, error-message,
     organization, and reference.

     Copyright (c) 2016 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).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119 (https://tools.ietf.org/html/rfc2119).

     This version of this YANG module is part of RFC XXXX
     (https://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  revision 2017-03-09 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: Using Markup in YANG Text Arguments";
  }

  extension text-media-type {
    argument type;
    description
      "This extension allows for specifying a media type that is used
       for markup in the arguments of the following YANG statements:

       - contact

       - description

       - error-message

       - organization



Lhotka                 Expires September 10, 2017               [Page 5]


Internet-Draft                 i-d-abbrev                     March 2017


       - reference

       The *text-media-type* extension statement MAY be used at the
       top level of a module or submodule, i.e., as a substatement of
       *module* or *submodule*, and no more than once. The declared
       media type applies throughout the module or submodule.

       The argument SHOULD be a media type registered by IANA in the
       *text* registry. Media type parameters MAY be present.

       This YANG extension is only indicative and optional to
       implement. Tools MAY ignore it completely or support just a
       subset of markup directives that are available for a given
       media type.";
    reference
      "- IANA: Media Types, 2016-12-21. Available [online]
         (http://www.iana.org/assignments/media-types/media-types.xhtml)

       - [RFC 6838](https://tools.ietf.org/html/rfc6838): Media Type
         Specifications and Registration Procedures";
  }
}

<CODE ENDS>

5.  IANA Considerations

   RFC Editor: In this section, replace all occurrences of 'XXXX' with
   the actual RFC number and all occurrences of the revision date below
   with the date of RFC publication (and remove this note).

   This document registers the following namespace URI in the "IETF XML
   registry" [RFC3688]:

   URI: urn:ietf:params:xml:ns:yang:ietf-yang-text-media-type
   Registrant Contact: The IESG.
   XML: N/A, the requested URI is an XML namespace.

   This document registers the following YANG module in the "YANG Module
   Names" registry [RFC6020]:

   Name:         ietf-yang-text-media-type
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-yang-text-media-type
   Prefix:       ymt
   Reference:    RFC XXXX






Lhotka                 Expires September 10, 2017               [Page 6]


Internet-Draft                 i-d-abbrev                     March 2017


6.  Security Considerations

   The "text-media-type" extension defined in this document provides
   information that is completely optional.  YANG modules and submodules
   in which it is present have to satisfy all rules of the YANG
   language.  The extension therefore doen't introduce any new threats.

7.  References

7.1.  Normative References

   [IANA-MEDIA-TYPES]
              Internet Assigned Numbers Authority, "Media Types", 12
              2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6020>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <http://www.rfc-editor.org/info/rfc6838>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <http://www.rfc-editor.org/info/rfc7950>.

7.2.  Informative References

   [RFC7764]  Leonard, S., "Guidance on Markdown: Design Philosophies,
              Stability Strategies, and Select Registrations", RFC 7764,
              DOI 10.17487/RFC7764, March 2016,
              <http://www.rfc-editor.org/info/rfc7764>.







Lhotka                 Expires September 10, 2017               [Page 7]


Internet-Draft                 i-d-abbrev                     March 2017


Author's Address

   Ladislav Lhotka
   CZ.NIC

   Email: lhotka@nic.cz













































Lhotka                 Expires September 10, 2017               [Page 8]


Html markup produced by rfcmarkup 1.122, available from https://tools.ietf.org/tools/rfcmarkup/