Comparing Two Approaches to Compensable Flow Composition

Abstract

Abstract. Web services composition is an emerging paradigm for the integration of long running business processes, attracting the interest of both Industry, in terms of XML-based standards for business description, and Academy, exploiting process description languages. The key challenging aspects to model are orchestration workflows, choreography of exchanged messages, fault handling, and transactional integrity with compensation mechanisms. Few recent proposals attempted to mitigate the explosion of XML-constructs in ad hoc standards by a careful selection of a small set of primitives related to the above aspects. This papers clarifies analogies and differences between two such recent process description languages: one based on interleaving trace semantics and the other on concurrent traces. We take advantage of their comparison to characterise and relate four different coordination policies for compensating parallel processes. Such policies differ on the way in which the abort of a process influences the execution of sibling processes, and whether compensation is distributed or centralised.

A Calculus for Orchestration of Web Services

“…This is, for example, the case of [19,20,23,24] that present timed and untimed extensions of thecalculus, called Û and Û ½ , tailored to study a simplified version of the scope construct of WS-BPEL. Other proposals on the formalization of flow compensation are [5,4] that give a more compact and closer description of the Sagas mechanism [13] for dealing with long running transactions. We have focused on service orchestration rather than on service choreography.…”

Decidability Results for Dynamic Installation of Compensation Handlers

“…The only other results comparing the expressive power of primitives for transactions and compensations are in the field of SAGAs [9]/cCSP [10], but their setting allows only for isolated activities, since it does not consider communication. There are two kinds of results: a few papers compare different variants of SAGAs [6,18,7], while others use SAGAs-like calculi as specifications for π-style processes [21,11]. Both kinds of results cannot be easily compared with ours.…”

Sessions and Pipelines for Structured Service Programming

“…We also plan to investigate the use of the session-closing mechanism for programming long-running transactions and related compensation policies in the context of web applications, in the vein e.g. of [7,18], and its relationship with the cCSP and the sagas-calculi discussed in [5].…”