Interoperability among independently evolving web services

Abstract. The increasing popularity of XML Web services motivates us to examine if it is feasible to substitute one vendor service for another when using a Web-based application, assuming that these services are “derived from ” a common base. If such substitution were possible, end users could use the same application with a variety of back-end vendor services, and the vendors themselves could compete on price, quality, availability, etc. Interoperability with substituted services is non-trivial, however, and four types of incompatibilities may arise during such interoperation – structural, value, encoding and semantic. We address these incompatibilities three-fold: (1) static and dynamic analysis tools to infer whether an application is compatible with a substituted service, (2) semiautomatically generated middleware components called cross-stubs that actually resolve incompatibilities and enable interoperation with substituted services, and (3) a lightweight mechanism called multi-option types to enable applications to be written from the ground up in an interoperation-friendly manner. Using real applications and services as examples, we both demonstrate and evaluate our tools and techniques for enabling interoperation with substituted services.