International Journal of Cooperative Information Systems

This paper addresses the issue of automatic service composition. We first develop a framework in which the exported behavior of a service is described in terms of a so-called execution tree, that is an abstraction for its possible executions. We then study the case in which such exported behavior (i.e. the execution tree of the service) can be represented by a finite state machine (i.e. finite state transition system). In this specific setting, we devise sound, complete and terminating techniques both to check for the existence of a composition, and to return a composition, if one exists. We also analyze the computational complexity of the proposed algorithms. Finally, we present an open source prototype tool, called (E-Service Composer), that implements our composition technique. To the best of our knowledge, our work is the first attempt to provide a provably correct technique for the automatic synthesis of service composition, in a framework where the behavior of services is explicitly specified.

Standards like SOAP, WSDL, and UDDI facilitate the proliferation of services. Based on these technologies, processes are a means to combine services to applications and to provide new value-added services. For large information systems, a centralized process engine is no longer appropriate due to limited scalability. Instead, in this paper, we propose a distributed and decentralized process engine that routes process instances directly from one peer to the next. Such a peer-to-peer process execution promises good scalability characteristics since it is able to dynamically balance the load of processes and services among all available service providers. Therefore, navigation costs only accumulate on peers that are directly involved in the execution. However, this requires sophisticated strategies for the replication of meta-data for peer-to-peer process execution. Especially, replication mechanisms should avoid frequent accesses to global information repositories. In our system, called OSIRIS (Open Service Infrastructure for Reliable and Integrated Process Support), we deploy a publish/subscribe-based replication scheme together with freshness predicates to significantly reduce replication costs. This way, OSIRIS can support process-based applications in a dynamically evolving system without limiting scalability and correctness. Experiments have shown very promising results with respect to scalability. In addition, OSIRIS provides a flexible infrastructure that can be extended seamlessly in a modular way. This paper demonstrates the extension towards distributed concurrency control.

The web-services stack of standards is designed to support the reuse and interoperation of software components on the web. A critical step in the process of developing applications based on web services is service discovery, i.e. the identification of existing web services that can potentially be used in the context of a new web application. Discovery through catalog-style browsing (such as supported currently by web-service registries) is clearly insufficient. To support programmatic service discovery, we have developed a suite of methods that assess the similarity between two WSDL (Web Service Description Language) specifications based on the structure of their data types and operations and the semantics of their natural language descriptions and identifiers. Given only a textual description of the desired service, a semantic information-retrieval method can be used to identify and order the most relevant WSDL specifications based on the similarity of the element descriptions of the available specifications with the query. If a (potentially partial) specification of the desired service behavior is also available, this set of likely candidates can be further refined by a semantic structure-matching step, assessing the structural similarity of the desired vs the retrieved services and the semantic similarity of their identifiers. In this paper, we describe and experimentally evaluate our suite of service-similarity assessment methods.

Software solutions to automate the procurement of web services are gaining importance when technology evolves, the number of providers increases and the needs of the clients become more complex. There are several proposals in this field, but they all have important drawbacks, namely: many of them are not able to check offers and demands for internal consistency; selecting the best offer usually relies on evaluating linear objective functions, which is quite a naive solution; the language to express offers is usually less expressive than the language to express demands; and, last but not least, providers cannot impose constraints on their clients. In this article, we present a solution to overcome these problems that relies on constraint programming; furthermore, we present a run-time framework, some experimental results, and a comparison with other proposals.

The web and converged services paradigm promises tremendous flexibility in the creation of rich composite services for enterprises and end users. The flexibility and richness offers the possibility of highly customized, individualized services for the end user and hence revenue generating services for service providers (e.g. ASPs, telecom network operators, ISPs). But how can end users (and enterprises) specify their preferences when a myriad of possibilities and potential circumstances need to be addressed? In this paper, we advocate a solution based on policy management where user preferences are specified through forms but translated into rules in a high-level policy language. This paper identifies the requirements for this kind of interpretation, and describes the Houdini system (developed at Bell Labs) which offers a rich rule-based language and a framework that supports intuitive, forms-based provisioning interfaces.

An error-comprising workflow definition of mission critical business process might incur serious problems to an enterprise. Although workflow designer is responsible for the error-comprising workflow definitions, workflow system has to be equipped with an intelligent workflow modeling tool preventing workflow designers from specifying error-comprising workflow definitions. Faults and mistakes of process designers have to be detected and reported to them by the tool at workflow build time. Access conflicts and improper specification of exceptions are two typical examples of such an error-comprising workflow definition. In this paper, we develop an access conflict detection and an uncaught exception detection techniques. A simple workflow definition language, named SWDL, is developed and the techniques are successfully developed on SWDL using Set Constraint System. With slight modifications and scope restrictions, the proposed techniques can be used in any workflow definition language either by translating it into SWDL or by referring to the techniques for the developing its own techniques. This indicates that general conventional programming language analysis techniques can be used in the analysis of workflow definitions by introducing an intermediate workflow definition language and developing analysis techniques on it.