<multiplicity>*</multiplicity>
          </association>
        </field>
        <field>
          <name>optional</name>
          <version>4.0.0+</version>
          <description>
            Indicates the dependency is optional for use of this library. While the
            version of the dependency will be taken into account for dependency calculation if the

Term        = production_name | token [ "…" token ] | Group | Option | Repetition .
Group       = "(" Expression ")" .
Option      = "[" Expression "]" .
Repetition  = "{" Expression "}" .
</pre>

<p>
Productions are expressions constructed from terms and the following
operators, in increasing precedence:
</p>
<pre class="grammar">
|   alternation
()  grouping
[]  option (0 or 1 times)
{}  repetition (0 to n times)
</pre>