Enterprise information systems are currently developed as Web-based applications in the service-oriented architecture style, which is implied by the stack of Web services standards. One of the most critical aspects in enterprise information systems is to maintain their continuous operation as long as possible. Conventional service invocation mechanism identifies Web services with similar signatures found by a service discovery as distinctively different ones, resulting in the suspension of a service requester and the modification of its invocation procedures. In this paper, we propose a reasonable solution to realize runtime invocation of Web services, regarding structural similarities in service signatures as subsumption relations of XML scheme. Given Web services with subsumed signatures, this solution enables a service requester to invoke the Web services by translating the scheme types of the invocation parameters.