root/trunk/spec/value.dbk

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<article>
  <articleinfo>
    <title>
      Value Key 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:value</userinput>
          </para>
        </listitem>
      </varlistentry>

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

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

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

        <listitem>
          <para>
            Scalar.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Canonical:
          </para>
        </term>

        <listitem>
          <para>
            N/A (single format).
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Regexp:
          </para>
        </term>

        <listitem>
          <para>
            <userinput>=</userinput>
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <para>
            Definition:
          </para>
        </term>
        <listitem>
          <para>
            Specify the default value of a mapping.
          </para>

          <para>
            The <quote><userinput>=</userinput></quote> key is used to denote
            the "default value" of a mapping. In some cases, it is useful to
            evolve a schema so that a scalar value is replaced with a mapping.
            A processor may present a "scalar value" method that provides the
            value directly if the node is a scalar or returns the value of
            this key if the node is a mapping. If applications only access the
            scalar value through this interface then the schema may freely
            grow over time replacing scalar values with richer data constructs
            without breaking older processing systems.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>

    <example>
      <title><userinput>!!value</userinput> Examples</title>
<programlisting>
---     # Old schema
link with:
  - library1.dll
  - library2.dll
---     # New schema
link with:
  - = : library1.dll
    version: 1.2
  - = : library2.dll
    version: 2.3
</programlisting>
    </example>
  </section>
</article>