Abstract. We formally define an abstract executable semantics for the Business Process Execution Language for Web Services in terms of a distributed ASM. The goal of this work is to support the design and standardization of the language. “There is a need for formalism. It will allow us to not only reason about the current specification and related issues, but also uncover issues that would otherwise go unnoticed. Empirical deduction is not sufficient. ” – Issue #42, OASIS WSBPEL TC. The language definition assumes an infrastructure for running Web services on some asynchronous communication architecture. A business process is built on top of a collection of Web services performing continuous interactions with the outside world by sending and receiving messages over a communication network. The underlying execution model is characterized by its concurrent and reactive behavior making it particularly difficult to predict dynamic system properties with a sufficient degree of detail and precision under all circumstances. 1

Abstract—In some distributed and mobile communication models, a message disappears in one place and miraculously appears in another. In reality, of course, there are no miracles. A message goes from one network to another; it can be lost or corrupted in the process. Here, we present a realistic but high-level communication model where abstract communicators represent various nets and subnets. The model was originally developed in the process of specifying a particular network architecture, namely, the Universal Plug and Play architecture. But, it is general. Our contention is that every message-based distributed system, properly abstracted, gives rise to a specialization of our abstract communication model. The purpose of the abstract communication model is not to design a new kind of network; rather, it is to discover the common part of all message-based communication networks. The generality of the model has been confirmed by its successful reuse for very different distributed architectures. The model is based on distributed abstract state machines. It is implemented in the specification language AsmL and is used for testing distributed systems. Index Terms—Abstract state machines, communication protocols, computer networks, distributed systems, requirement specification, system modeling, testing of distributed systems. æ

Abstract. We define an abstract operational semantics for the Business state machine (ASM) formalism. This way, we model the dynamic properties of the key language constructs through the construction of a BPEL abstract machine in terms of a distributed real-time ASM. Specifically, we focus here on the process execution model and the underlying execution lifecycle of BPEL activities. The goal of our work is to provide a well defined semantic foundation for establishing the key language attributes. The resulting abstract machine model provides a comprehensive and robust formalization at three different levels of abstraction.

In hardware and software design model checkers are nowadays used with success to verify properties of system components [23]. The limits of the approach to cope with the size and the complexity of modern computer-based systems are felt when it comes to provide evidence of the trustworthiness of the entire system that has been built out of verified components. To achieve this task one has to experimentally validate or to mathematically verify the composition of the system. This reveals a gap between the finite state machine (FSM) view of model-checkable components and the architectural system view. In this paper we show how Abstract State Machines (ASM) can be used to fill this gap for both design and analysis, using a flexible concept of ASM component. 1

Abstract. In this paper we present an approach to model checking abstract state machines using the Spin model checker. We give an algorithm for automatically transforming ASM specifications written in CoreASM [1] into Promela specifications. Though an algorithm for translating ASMs into Promela has already been presented in [2], our method supports a more powerful ASM language, including support for n-ary functions and extended rule forms. Specifically, our translation also supports distributed abstract state machines. 1

A large class of legacy software systems, developed and maintained over many years, can also be termed sequential software systems in that independent parts of the system requires exclusive access to shared data during its entire execution. This requirement originates from design decisions on non-preemptive execution, and when the underlying architecture is a single-processor one, this is sufficient to protect the shared data. The problem arises when this architecture is to be replaced by a multi-processor ditto; since different tasks (still executed in a non-preemptive fashion, but on different processors) now may access, and update, the same data concurrently, non-preemptive execution does not protect the shared data any longer. To the above problem, we propose a solution based on a program analysis that can decide when parallel execution of the current software is safe in the sense that the parallel execution does not result in data interference. As a formal basis for such an analysis, the formal semantics of the language in question has to be considered. This thesis presents an operational semantics for the language PLEX, used to program the AXE telephone exchange system, in which the above mentioned properties are found: independent pieces of software, executed in a non-preemptive fashion, together with unprotected, shared data. 1 1

The Business Process Execution Language for Web Services (BPEL) is a forthcoming industrial standard for automated business processes, proposed by the OASIS1 Web Services BPEL Technical Committee. BPEL is a service orchestration language which extends the underlying Web services interaction model and enables Web services to support long running business transactions. state machine (ASM) paradigm. Specifically, we model the dynamic properties of the key language constructs through the construction of a BPEL Abstract Machine in terms of partially ordered runs of distributed real-time ASMs. The goal of our work is to provide a well defined semantic foundation for establishing the key language attributes by eliminating deficiencies hidden in the informal language definition. This work combines two well-defined ASM refinement techniques to complement our previous efforts on the core model of the BPEL Abstract Machine. First, we elaborate the core model with regard to structural and behavioural aspects to make it more robust and

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