%R 10.1007/11767954_10 %B COORDINATION %X We tackle the problem of providing rigorous formal foundations to current software engineering technologies for web services. We focus on two of the most used XML-based languages for web services: WSDL and WS-BPEL. To this aim, first we select an expressive subset of WS-BPEL, with special concern for modeling the interactions among web service instances in a network context, and define its operational semantics. We call ws-calculus the resulting formalism. Then, we put forward a rigorous typing discipline that formalizes the relationship existing between ws-calculus terms and the associated WSDL documents and supports verification of their compliance. We prove that the type system and the operational semantics of ws-calculus are ?sound? and apply our approach to an example application involving three interacting web services. %E Paolo Ciancarini %E Herbert Wiklicky %L eprints419 %D 2006 %S Lecture Notes in Computer Science %A Alessandro Lapadula %A Rosario Pugliese %A Francesco Tiezzi %V 4038 %I Springer %O ?Springer-Verlag Berlin Heidelberg 2006. The original publication is available at www.springerlink.com %T A WSDL-Based Type System for WS-BPEL %P 145-163