
9945-1:1990 <a href="#ref-posix">[POSIX.1]</a>:</p>

<dl>
<dt>Implementation-defined</dt>

<dd>A value or behavior is implementation-defined when it is left
to the implementation to define [and document] the corresponding
requirements for correct document construction.</dd>

<dt>May</dt>

<dd>With respect to implementations, the word "may" is to be
interpreted as an optional feature that is not required in this
specification but can be provided. With respect to <a href= 
"#docconf">Document Conformance</a>