Real-scale Semantic Web applications, such as Web Portals and E-Marketplaces, require the management of voluminous metadata repositories containing descriptive information (i.e., metadata) about the available Web resources and services. Better knowledge about the meaning, usage, accessibility or quality of these resources and services will considerably facilitate the automated processing of both Web content and services. In this context, the Resource Description Framework (RDF) enables the creation and exchange of metadata as any other Web data. Although large volumes of RDF descriptions are already appearing (e.g., as exported Portal catalogs or service descriptions), sufficiently expressive declarative languages for querying both RDF descriptions and schemas are still missing. In this paper, we propose RQL, a new RDF query language, relying on a formal graph model that permits the interpretation of superimposed resource descriptions. RQL is an OQL-inspired adaptation of XML query languages to the peculiarities of RDF but, foremost, is an extension of this functionality for uniformly querying both descriptions and schemas. We illustrate the syntax, semantics and core functionality of RQL bymeans of a set of benchmark queries and report on the performance of RSSDB, our persistent RDF Store, for storing and querying voluminous RDF descriptions.

Emerging Web services standards enable the development of large-scale applications in open environments. In particular, they enable services to be dynamically bound. However, current techniques fail to address the critical problem of selecting the right service instances. Service selection should be determined based on user preferences and business policies, and consider the trustworthiness of service instances. We propose a multiagent approach that naturally provides a solution to the selection problem. This approach is based on an architecture and programming model in which agents represent applications and services. The agents support considerations of semantics and quality of service (QoS). They interact and share information, in essence creating an ecosystem of collaborative service providers and consumers. Consequently, our approach enables applications to be dynamically configured at runtime in a manner that continually adapts to the preferences of the participants. Our agents are designed using decision theory and use ontologies. We evaluate our approach through simulation experiments.

Web services are becoming a standard method of sharing data and functionality among loosely-coupled systems. We propose a generalpurpose Web Service Management System (WSMS) that enables querying multiple web services in a transparent and integrated fashion. This paper tackles a first basic WSMS problem: query optimization for Select-Project-Join queries spanning multiple web services. Our main result is an algorithm for arranging a query’s web service calls into a pipelined execution plan that optimally exploits parallelism among web services to minimize the query’s total running time. Surprisingly, the optimal plan can be found in polynomial time even in the presence of arbitrary precedence constraints among web services, in contrast to traditional query optimization where the analogous problem is NP-hard. We also give an algorithm for determining the optimal granularity of data “chunks ” to be used for each web service call. Experiments with an initial prototype indicate that our algorithms can lead to significant performance improvement over more straightforward techniques. 1.

The ability to create reliable and scalable virtual organisations (VOs) on demand in a dynamic, open and competitive environment is one of the major challenges that underlie Grid computing. In response, in the CONOISE-G project, we are developing an infrastructure to support robust and resilient virtual organisation formation and operation. Specifically, CONOISE-G provides mechanisms to assure effective operation of agent-based VOs in the face of disruptive and potentially malicious entities in dynamic, open and competitive environments. In this paper, we describe the CONOISE-G system, outline its use in the context of VO formation and perturbation, and review current efforts to progress the work to deal with unreliable information sources. 1

Abstract. OWL-S allows selecting, composing and invoking Web Services descriptions, invocation uses low level grounding ones, while composition needs to consider both high and low level descriptions. In our setting, two Web Services are to be composed so that output from the upstream one is used to create input for the downstream one. These Web Services may have different data models but are related to each other through high and low level descriptions. Correspondences must be found between components of the upstream data type and the downstream ones. Low level data transformation functions may be required (e.g. unit conversions, data type conversions). The components may be arranged in different XML tree structures. Thus, multiple data transformations are necessary: reshaping the message tree, matching leaves by corresponding types, translating through ontologies, and calling conversion functions. Our prototype compiles these transformations into a set of data transformation rules, using our tableau-based ALC Description Logic reasoner to reason over the given OWL-S and WSDL descriptions, as well as the related ontologies. A resolution-based inference mechanism for running these rules is embedded in an inference queue that conducts data from the upstream to the downstream service, running the rules to perform the data transformation in the process. 1

In principle, with Web services, application creation is simply a matter of finding and selecting the right services and composing them into a solution. However, current techniques do not address the problem of selecting the best or even a desirable service from among those matching a given interface. We propose an approach wherein middle agents serve as proxies for Web services to assist an application in selecting implementations that best match the quality criteria of the application. This approach supports the dynamic and potentially optimal selection of services and supports the natural formation of communities of agents helping each other evaluate the same services. This approach gets us close to vision of autonomic computing, wherein computational resources are selfmanaging and self-configuring. A prototype of this system is under development and evaluation.

Business process management in open environments poses special challenges. In particular, open environments are dynamic thereby requiring frequent changes in business processes. In current business process modeling approaches, such changes are handled in an ad hoc manner. It is not clear what needs to be changed and where, to accommodate a change. In this paper, we build on our previous work on business protocols to handle the challenge of design adaptability. The basic mechanism that facilitates such adaptability is that of protocol composition. We also provide a semantics for the protocols and their composition in causal logic. Through a real business scenario of auto-insurance claim processing, we demonstrate how a wide range of adaptations can be handled naturally and systematically via protocol composition. The illustrated adaptations have been prototyped. 1

An important aspect of service-centric systems (i.e. systems composed of services) is the ability to support service discovery at run-time in order to cope with unavailable or malfunctioning services. In this paper we present a framework that supports run-time service discovery. The central characteristic of this framework is the combination of components for monitoring the compliance of service-centric systems with requirements at run-time and components for discovering services at run-time. The framework uses the former components to detect violations of requirements at run-time and uses the specifications of the violated requirements to generate queries for discovering services that could substitute for malfunctioning services. It also uses queries derived from the process specification for service discovery. These queries incorporate both structural and behavioural aspects of the required services. 1.

To fully utilize web-services, users and applications should be able to discover, deploy, compose and synthesize services automatically. This automation can take place only if a formal semantic description of the web-services is available. In this paper we present the design of USDL (Universal Service-Semantics Description Language), a language for formally describing the semantics of web-services. USDL is based on the Web Ontology Language (OWL) and employs Word-Net as a common basis for understanding the meaning of services. USDL can be regarded as formal program documentation that will allow sophisticated conceptual modeling and searching of available web-services, automated service composition, and other forms of automated service integration. The design of USDL is presented, along with examples, and its formal semantics given. A theory of service composition for USDL is presented and proved sound and complete. 1

Using archetypes is a promising approach in providing semantic interoperability among healthcare systems. To realize archetype based interoperability, the healthcare systems need to discover the existing archetypes based on their semantics; annotate their archetypes with ontologies; compose templates from archetypes and retrieve corresponding data from the underlying medical information systems. In this paper, we describe how ebXML Registry semantic constructs can be used for annotating, storing, discovering and retrieving archetypes. For semantic annotation of archetypes, we present an example archetype metadata ontology and describe the techniques to access archetype semantics through ebXML query facilities. We present a GUI query facility and describe how the stored procedures we introduce, move the semantic support beyond what is currently available in ebXML registries. We also address how archetype data can be retrieved from clinical information systems by using ebXML Web services. A comparison of Web service technology with ebXML messaging system is provided to justify the reasons for using Web services. 1.