Abstract
We identify significant weaknesses in the original Abstract State Machine (ASM) based choreography algorithm of Web Service Modeling Ontology (WSMO), which make it impractical for use in semantic web service choreography engines. We present an improved algorithm which rectifies the weaknesses of the original algorithm, as well as a practical, fully functional choreography engine implementation in Flora-2 based on the improved algorithm. Our improvements to the choreography algorithm include (i) the linking of the initial state of the ASM to the precondition of the goal, (ii) the introduction of the concept of a final state in the execution of the ASM and its linking to the postcondition of the goal, and (iii) modification to the execution of the ASM so that it stops when the final state condition is satisfied by the current configuration of the machine. Our choreography engine takes as input semantic web service specifications written in the Flora-2 dialect of F-logic. Furthermore, we prove the equivalence of ASMs (evolving algebras) and evolving ontologies in the sense that one can simulate the other, a first in literature. Finally, we present a visual editor which facilitates the design and deployment of our F-logic based web service and goal specifications.
Highlights
The idea of using service oriented architecture (SOA) to form an IT infrastructure for carrying out business-tobusiness interactions has gained a lot of attention in the last 15 years
We have found that (i) the implementation of choreography in WSMX was started but not completed, (ii) the implementation does not support parallelism and inconsistency checking is not even an issue, (iii) the implementation does not support intentional nondeterministic behavior necessitated by the Choose rule type, (iv) in the case of if- rules, if more than one lefthand side is satisfied by the current ontology state, right-hand sides of all matching rules are executed sequentially, without any consistency check of the actions performed, resulting in behavior that depends on the order of the rules
We identified important weaknesses in the original Abstract State Machine (ASM)-based choreography execution algorithm for Web Service Modeling Ontology (WSMO), which prevented it from being useful in a practical way, and improved it in order to remedy the identified weaknesses
Summary
The idea of using service oriented architecture (SOA) to form an IT infrastructure for carrying out business-tobusiness interactions has gained a lot of attention in the last 15 years. Our main contributions here can be summarized as (i) rectifying the original ASMbased choreography algorithm, (ii) proposing an F-logic specification of WSMO goal and web service choreographies as an effective alternative to the current specifications in WSML [20] and OCML [21], (iii) implementing the rectified choreography algorithm in Flora-2 [22, 23] with novel technics that adhere to theory of ASMs (missing in other implementations), (iv) validating the implemented Flora-2 engine through several realistic scenarios, (v) developing a visual editor to facilitate the design and deployment of semantic web services in a subset of the Flora-2 language that we adopted as our specification language, and (vi) proving the equivalence of ASMs ( known as evolving algebras [24]) and WSMO choreography specifications (commonly called evolving ontologies [25]) by providing appropriate mappings between them. In Appendix E in the Supplementary Materials we describe a scheme for converting JSON content into its Flora equivalent, a step that will be useful in grounding Flora-2 specified semantic web services into RESTful web services
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