Formal semantics and analysis of control flow in WS-BPEL

Web service composition refers to the creation of new (Web) services by combination of functionality provided by existing ones. This paradigm has gained significant attention in the Web services community and is seen as a pillar for building service-oriented applications. A number of domain-specific languages for service composition have been proposed with consensus being formed around a process-oriented language known as WS-BPEL (or BPEL). The kernel of BPEL consists of simple communication primitives that may be combined using control-flow constructs expressing sequence, branching, parallelism, synchronisation, etc. As a result, BPEL process definitions lend themselves to static flow-based analysis techniques. In this report, we describe a tool that performs two useful types of static checks and extracts meta-data to optimise dynamic resource management. The tool operates by translating BPEL processes into Petri nets and exploiting existing Petri net analysis techniques. It relies on a comprehensive and rigorously defined mapping of BPEL constructs into Petri net structures

Formal semantics and analysis of control flow in WS-BPEL

Web service composition refers to the creation of new (Web) services by combination of functionality provided by existing ones. This paradigm has gained significant attention in the Web services community and is seen as a pillar for building service-oriented applications. A number of domain-specific languages for service composition have been proposed with consensus being formed around a process-oriented language known as WS-BPEL (or BPEL). The kernel of BPEL consists of simple communication primitives that may be combined using control-flow constructs expressing sequence, branching, parallelism, synchronisation, etc. As a result, BPEL process definitions lend themselves to static flow-based analysis techniques. In this report, we describe a tool that performs two useful types of static checks and extracts meta-data to optimise dynamic resource management. The tool operates by translating BPEL processes into Petri nets and exploiting existing Petri net analysis techniques. It relies on a comprehensive and rigorously defined mapping of BPEL constructs into Petri net structures

Feasibility of EPC to BPEL Model Transformations Based on Ontology and Patterns

Model-Driven Engineering holds the promise of transforming\ud business models into code automatically. This requires the concept of\ud model transformation. In this paper, we assess the feasibility of model\ud transformations from Event-driven Process Chain models to Business\ud Process Execution Language specifications. To this purpose, we use a\ud framework based on ontological analysis and workflow patterns in order\ud to predict the possibilities/limitations of such a model transformation.\ud The framework is validated by evaluating the transformation of several\ud models, including a real-life case.\ud The framework indicates several limitations for transformation. Eleven\ud guidelines and an approach to apply them provide methodological support\ud to improve the feasibility of model transformation from EPC to\ud BPEL

Optimizing Computation of Recovery Plans for BPEL Applications

Web service applications are distributed processes that are composed of dynamically bounded services. In our previous work [15], we have described a framework for performing runtime monitoring of web service against behavioural correctness properties (described using property patterns and converted into finite state automata). These specify forbidden behavior (safety properties) and desired behavior (bounded liveness properties). Finite execution traces of web services described in BPEL are checked for conformance at runtime. When violations are discovered, our framework automatically proposes and ranks recovery plans which users can then select for execution. Such plans for safety violations essentially involve "going back" - compensating the executed actions until an alternative behaviour of the application is possible. For bounded liveness violations, recovery plans include both "going back" and "re-planning" - guiding the application towards a desired behaviour. Our experience, reported in [16], identified a drawback in this approach: we compute too many plans due to (a) overapproximating the number of program points where an alternative behaviour is possible and (b) generating recovery plans for bounded liveness properties which can potentially violate safety properties. In this paper, we describe improvements to our framework that remedy these problems and describe their effectiveness on a case study.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330

Models of High-Level Computation

Classical models of computation have been successful in capturing the very essence of individual computing devices. Although they are useful to understand computability power and limitations in the small, such models are not suitable to study large-scale complex computations. Accordingly, plenty of formalisms have been proposed in the last half century as an attempt to raise the level of abstraction, with the aim of describing not only a single computing device but interactions among a collection of them. In this paper, we encompass such formalisms into a common framework which we refer to as Models of High-Level Computation. We particularly discuss the semantics, some of the key properties, paradigms and future directions of such models

Visual analytics for soundness verification of process models

Soundness validation of process models is a complex task for process modelers due to all the factors that must be taken into account. Although there are tools to verify this property, they do not provide users with easy information on where soundness starts breaking and under which conditions. Providing insights such as states in which problems occur, involved activities, or paths leading to those states, is crucial for process modelers to better understand why the model is not sound. In this paper we address the problem of validating the soundness property of a process model by using a novel visual approach and a new tool called PSVis (Petri net Soundness Visualization) supporting this approach. The PSVis tool aims to guide expert users through the process models in order to get insights into the problems that cause the process to be unsoun

Message correlation in web services choreographies: a 4-phase validation method

The majority of large companies are adopting Service Oriented Architectures, mainly to automate their business processes, both centralized and distributed. This paper will focus on distributed business processes. At the moment there are two interesting ways to implement a distributed business process, via orchestration or choreography. Whereas an orchestration can be thought of as a service composition with a single participant taking the lead, a choreography is a decentralized collaboration between different autonomous participants. One of the most prominent remaining issues, associated with both approaches, is the correlation problem, which is addressed in this paper. We will show that the abstract overall view, provided by a choreography description, makes it possible to determine (even at design time) whether its interactions can be unambiguously correlated. It is shown that this correlation validation is more feasible to realize in case of choreographies than with orchestrations, due to the orchestration's limited view on the overall business process