A Rude Contract Language for Web Services

Several schema languages have been recently proposed for describing XML documents. The key notion of such languages is the subschema relation which is used for type checking. We present a schema language for modelling XML documents containing channel schemas with (input and output) capabilities and we describe two subschema algorithms. The first one uses a simulation relation; the second one examines the structure of the schemas. We demonstrate the equivalence of the algorithms and we discuss their computational complexity.