root/trunk/spec/pairs.dbk

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<article>
  <articleinfo>
    <title>
      Pairs Language-Independent Type for
      <trademark>YAML</trademark>&nbsp;Version&nbsp;1.1
    </title>

    <subtitle>
      Working Draft 2005-01-18
    </subtitle>

    <authorgroup>
      <author>
        <firstname>Oren</firstname>
        <surname>Ben-Kiki</surname>
        <email>oren@ben-kiki.org</email>
      </author>

      <author>
        <firstname>Clark</firstname>
        <surname>Evans</surname>
        <email>cce+yaml@clarkevans.com</email>
      </author>

      <author>
        <firstname>Brian</firstname>
        <surname>Ingerson</surname>
        <email>ingy@ttul.org</email>
      </author>
    </authorgroup>

    <copyright>
      <year>2001-2005</year>
      <holder>Oren Ben-Kiki<fo>,&nbsp;</fo></holder>
      <holder>Clark Evans<fo>,&nbsp;</fo></holder>
      <holder>Brian Ingerson</holder>
    </copyright>

    <legalnotice>
      This document may be freely copied provided it is not modified.
    </legalnotice>

    <abstract>
      <title>Status</title>

      <para>
       This specification is a draft reflecting consensus reached by members of
       the <ulink
       url="http://lists.sourceforge.net/lists/listinfo/yaml-core">yaml-core
       mailing list</ulink>. Any questions regarding this draft should be
       raised on this list.
      </para>
    </abstract>
  </articleinfo>

  <section>
    <variablelist>
      <varlistentry>
        <term>
          <para>
            URI:
          </para>
        </term>

        <listitem>
          <para>
            <userinput>tag:yaml.org,2002:pairs</userinput>
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Shorthand:
          </para>
        </term>

        <listitem>
          <para>
            <userinput>!!pairs</userinput>
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Kind:
          </para>
        </term>

        <listitem>
          <para>
            Sequence.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Definition:
          </para>
        </term>

        <listitem>
          <para>
            Ordered sequence of key:value pairs allowing duplicates.
          </para>

          <para>
            A common type used for modeling is the ordered list of named
            values, allowing duplicates. For example, this is one of the basic
            constructs used to model XML data. YAML provides a shorthand
            notation for representing this data type as a sequence of one-key
            mappings.
          </para>

          <para>
            Most programming languages do not have a built-in native data type
            for supporting pairs. Such data types are usually provided by
            libraries. If no such data type is available, an application may
            resort to loading <userinput>!!pairs</userinput> into a native
            array of hash tables containing one key each.
          </para>

          <para>
            The <userinput>!!pairs</userinput> tag may be given explicitly.
            Alternatively, the application may choose to implicitly type a
            sequence of single-key mappings to pairs. In this case, an explicit
            <userinput>!!seq</userinput> transfer must be given to sequences of
            single-key mappings that do not represent pairs.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>

    <example>
      <title><userinput>!!pairs</userinput> Examples</title>
<programlisting>
# Explicitly typed pairs.
Block tasks: !!pairs
  - meeting: with team.
  - meeting: with boss.
  - break: lunch.
  - meeting: with client.
Flow tasks: !!pairs [ meeting: with team, meeting: with boss ]
</programlisting>
    </example>
  </section>
</article>