@Override
    protected boolean isOptional()
    {
      return false;
    }
<ul>
<li> check structure of Arguments:
<ol>
<li> First arg should be a String
<li> then there should be an even number of Arguments:
String, expression; expression should be Convertible to Boolean.
<li> finally there should be a String.
</ol>
<li> convert pattern into a NNode chain.
<li> convert symbol args into a Symbol Map.
<li> parse selectList into SelectList struct. The inputOI used to translate
these expressions should be based on the
columns in the Input, the 'path.attr'
</ul>
ql/src/java/org/apache/hadoop/hive/ql/udf/ptf/MatchPath.java