Implementors can define MATCHER_RELATIVE_NAMESPACE constant. If so, getMatcher() will return instances of objects relative to this namespace if $matcherIdentifier argument doesn't begin with a '\' (FQ class name).
Inheritance: implements eZ\Publish\Core\MVC\Symfony\Matcher\MatcherFactoryInterface
 protected function getMatcher($matcherIdentifier)
 {
     $matcher = parent::getMatcher($matcherIdentifier);
     if (!$matcher instanceof BlockMatcherInterface) {
         throw new InvalidArgumentException('Matcher for Blocks must implement eZ\\Publish\\Core\\MVC\\Symfony\\Matcher\\Block\\MatcherInterface.');
     }
     return $matcher;
 }
 protected function getMatcher($matcherIdentifier)
 {
     @trigger_error("ContentBasedMatcherFactory is deprecated, and will be removed in ezpublish-kernel 6.1.\n" . 'Use the ServiceAwareMatcherFactory with the relative namespace as a constructor argument.', E_USER_DEPRECATED);
     $matcher = parent::getMatcher($matcherIdentifier);
     if (!$matcher instanceof ContentBasedMatcherInterface) {
         throw new InvalidArgumentException('Content based Matcher must implement eZ\\Publish\\Core\\MVC\\Symfony\\Matcher\\ContentBased\\MatcherInterface.');
     }
     return $matcher;
 }