On-the-fly construction of provably correct service compositions – templates and proofs

• Create service compositions from templates.
• Proof calculus to verify templates.
• Compositions are provably correct by construction.

Today, service compositions often need to be assembled or changed on-the-fly, which leaves only little time for quality assurance. Moreover, quality assurance is complicated by service providers only giving information on their services in terms of domain specific concepts with only limited semantic meaning.In this paper, we propose a method for constructing service compositions based on pre-verified templates. Templates, given as workflow descriptions, are typed over a (domain-independent) template ontology defining concepts and predicates. Their meaning is defined by an abstract semantics, leaving the specific meaning of ontology concepts open, however, only up to given ontology rules. Templates are proven correct using a Hoare-style proof calculus, extended by a specific rule for service calls. Construction of service compositions amounts to instantiation of templates with domain-specific services. Correctness of an instantiation can then simply be checked by verifying that the domain ontology (a) adheres to the rules of the template ontology, and (b) fulfills the constraints of the employed template.