Pervasive computing environments are populated with networked services, i.e., autonomous software entities, providing a number of functionalities. One of the most challenging objectives to be achieved within these environments is to assist users in realizing tasks that integrate on the fly functionalities of the networked services opportunely according to the current pervasive environment. Towards this purpose, we present COCOA, a solution for COnversation-based service COmposition in pervAsive computing environments with QoS support. COCOA provides COCOA-L, an OWL-S based language for the semantic, QoSaware specification of services and tasks, which further allows the specification of services and tasks conversations. Moreover, COCOA provides two mechanisms: COCOA-SD for the QoS-aware semantic service discovery and COCOA-CI for the QoS-aware integration of service conversations towards the realization of the user task’s conversation. The distinctive feature of COCOA is the ability of integrating on the fly the conversations of networked services to realize the conversation of the user task, by further meeting the QoS requirements of user tasks. Thereby, COCOA allows the dynamic realization of user tasks according to the specifics of the pervasive computing environment in terms of available services and by enforcing valid service consumption. 1

Web service composition refers to the creation of new (Web) services by combining functionality provided by existing ones. 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, synchronization, etc. We present a comprehensive and rigorously defined mapping of BPEL constructs onto Petri net structures and use this for the analysis of various dynamic properties related to unreachable activities, conflicting messages, garbage collection, conformance checking, and deadlocks and lifelocks in interaction processes. We use a mapping onto Petri nets because this allows us to use existing theoretical results and analysis tools. Unlike approaches based on finite state machines, we do not need to construct the state space and can use structural analysis (e.g., transition invariants) instead. We have implemented a tool that translates BPEL processes into Petri nets and then applies Petri-net-based analysis techniques. This tool has been tested on different examples and has been used to answer a variety of questions.

The use of XML as the de facto data exchange standard has allowed integration of heterogeneous web based software systems regardless of implementation platforms and programming languages. On the other hand, the rich tree-structured data representation, and the expressive XML query languages (such as XPath) make formal specification and verification of software systems that manipulate XML data a challenge. In this paper, we present our initial efforts in automated verification of XML data manipulation operations using the SPIN model checker. We present algorithms for translating (bounded) XML data and XPath expressions to Promela, the input language of SPIN. The techniques presented in this paper constitute the basis of our Web Service Analysis Tool (WSAT) which verifies LTL properties of composite web services.

In this paper we describe tool support for a modelbased approach to verifying compositions of web service implementations. The tool supports verification of properties created from design specifications and implementation models to confirm expected results from the viewpoints of both the designer and implementer. Scenarios are modeled in UML, in the form of Message Sequence Charts (MSCs), and then compiled into the Finite State Process (FSP) algebra to concisely model the required behavior. BPEL4WS implementations are mechanically translated to FSP to allow an equivalence trace verification process to be performed. By providing early design verification and validation, the implementation, testing and deployment of web service compositions can be eased through the understanding of the behavior exhibited by the composition. The tool is implemented as a plug-in for the Eclipse development environment providing cooperating tools for specification, formal modeling and trace animation of the composition process. 1.

Abstract. Due to the large success of wireless networks and portable devices, the pervasive computing paradigm is becoming a reality. One of the most challenging objectives to be achieved in pervasive computing environments is to allow a user to perform a task by composing on the fly the environment’s service and resource components. However, existing approaches commonly assume that networked components have been developed to integrate in terms of interfaces and conversations, which restricts the user’s ability to fully exploit the diversity of the pervasive computing components. In order to overcome this constraint, we propose a solution for ad hoc composition of pervasive computing components, based on the Web services and Semantic Web paradigms. The main feature of our solution is the ability to integrate on the fly a number of Web services ’ conversation fragments to reconstruct a conversation enabling the target user task. 1

Abstract. A major challenge in pervasive computing environments is to provide users with complex, context-sensitive applications, dynamically composed from networked services. In this paper, we present an approach to the dynamic, context-aware composition of services to perform user tasks, i.e., software applications abstractly described on the user’s handheld device. Both networked services and user tasks are modeled as semantic Web services in OWL-S extended with context information. The distinctive feature of our solution is the ability to compose Web services that expose complex behaviors (conversations) to realize a user task that itself has a complex behavior. Furthermore, the context-related requirements of the task are met by aggregating the context-sensitive behaviors of the individual services. 1

Business Process Modelling Notation (BPMN), developed by the Business Process Management Initiative (BPMI), intends to bridge the gap between business process design and implementation. However, the specification of the notation does not include a formal semantics. This paper shows how a subset of the BPMN can be given a process semantics in Communicating Sequential Processes. Such a semantics allows developers to formally analyse and compare BPMN diagrams. Two simple examples of business processes are included. 1

Abstract. Web service composition has been the subject of a number of standardisation initiatives. These initiatives have met various difficulties and had mixed degrees of success, and none of them has yet attained both de facto and de jure status. This paper reviews two of these initiatives with respect to a framework wherein service composition is approached from multiple interrelated perspectives. One conclusion is that standardisation initiatives in this area have not been built on top of an explicitly defined overarching conceptual foundation. The paper outlines a research agenda aimed at identifying requirements and concepts that should be addressed by and incorporated into these standards.

Abstract. BPEL is currently the most widespread language for composing Web services, but it lacks formal semantics. YAWL is a workflow language with a well defined formal semantics that implements the most common workflow patterns. In this paper we provide a methodology for translating BPEL processes into YAWL workflows, thus paving the way for the formal analysis, aggregation and adaptation of BPEL processes. The approach we propose defines a YAWL pattern for each BPEL activity. The translation of a BPEL process reduces then to suitably instantiating and interconnecting the patterns of its activities. 1

Abstract. Web services composition is an emerging paradigm for enabling application integration within and across organizational boundaries. Current Web services composition proposals, such as BPML, WS-BPEL, WSCI, and OWL-S, provide solutions for describing the control and data flows in Web service composition. However, such proposals remain at the descriptive level, without providing any kind of mechanisms or tool support for analysis and verification. Therefore, there is a growing interest for the verification techniques which enable designers to test and repair design errors even before actual running of the service, or allow designers to detect erroneous properties and formally verify whether the service process design does have certain desired properties. In this paper, we propose to verify Web services composition using an event driven approach. We assume Web services that are coordinated by a composition process expressed in WSBPEL and we use Event Calculus to specify the properties and requirements to be monitored. 1