The API of the evaluation module contains discrete functions for schema, patterns, rules and assertions. This means that a complete schema is not required in order to perform evaluation of these components in isolation. One possible and likely application of this technique would be unit testing. The following is an example taken from the XQS test suite itself:

(:~ active pattern processed :)
declare %unit:test function _:process-pattern()
{
  let $result := eval:pattern(
    <sch:pattern id='e' name='f' role='g'>
      <sch:rule context='*' id='a' name='b' role='c' flag='d'/>
    </sch:pattern>,
    map{'instance':document{<foo/>}, 'globals':map{}}
  )
  return unit:assert-equals(
    $result,
    (<svrl:active-pattern id='e' name='f' role='g'/>,
    <svrl:fired-rule context='*' id='a' name='b' role='c' flag='d'/>)
  )
};

Here, the call to eval:pattern() (shown in bold) evaluates the pattern passed in against the context provided by the second, map argument. In this instance, the unit test is to check that patterns and rules are reported correctly in SVRL, but the user can extend this approach elsewhere via calls to eval:rule() and eval:assertion(); further examples of this appear in the XQS test suite.^[43]