Contains interfaces that extend `Signature` to provide additional information about each possible join point signature. This additional information can be accessed by casting a Signature object to the appropriate type, i.e.

      before(): call(* *(..)) {
          MethodSignature sig = (MethodSignature)thisJoinPoint.getSignature();
          ...
      }

This package also contains `SourceLocation` that provides information about the location in source code that corresponds to a particular join point.