Checks, if the resolver will accept a name.
Variable name to look up.
True, if Resolver will provide a value for the name, otherwise false.
Retrieves value for a name.
Variable name to look up
Value bound to that name. If the implementation cannot provide a value, it should return null.
Associates a value with a name.
Variable name to (re-)define
Value to associate with the name. An implementation is not required to allow value setting. If it doesn't, it should silently ignore the request.