Because we can process only a tiny fraction of information available on the Web, we must turn to machines for help in processing and analyzing its contents. With current technology, machines cannot understand and interpret the meaning of the information in natural-language form, which is how most Web information is represented today. We need a Semantic Web to express information in a precise, machine-interpretable form, so software agents processing the same set of data share an understanding of what the terms describing the data mean.

Systems and infrastructures are currently being developed to support Web services. The main idea is to encapsulate an organization’s functionality within an appropriate interface and advertise it as Web services. While in some cases Web services may be utilized in an isolated form, it is normal to expect Web services to be integrated as part of workflow processes. The composition of workflow processes that model e-service applications differs from the design of traditional workflows, in terms of the number of tasks (Web services) available to the composition process, in their heterogeneity, and in their autonomy. Therefore, two problems need to be solved: how to efficiently discover Web services – based on functional and operational requirements – and how to facilitate the interoperability of heterogeneous Web services. In this paper, we present a solution within the context of the emerging Semantic Web, that includes use of ontologies to overcome some of the problems. We start by illustrating the steps involved in the composition of a workflow. Two of these steps are the discovery of Web services and their posterior integration into a workflow. To assist designers with those two steps, we have devised an algorithm to simultaneously discover Web services and resolve heterogeneity among their interfaces and the workflow host. Finally, we describe a prototype that has been implemented to illustrate how discovery and interoperability functions are achieved.

Conjunctive queries play an important role as an expressive query language for Description Logics (DLs). Although modern DLs usually provide for transitive roles, it was an open problem whether conjunctive query answering over DL knowledge bases is decidable if transitive roles are admitted in the query. In this paper, we consider conjunctive queries over knowledge bases formulated in the popular DL SHIQ and allow transitive roles in both the query and the knowledge base. We show that query answering is decidable and establish the following complexity bounds: regarding combined complexity, we devise a deterministic algorithm for query answering that needs time single exponential in the size of the KB and double exponential in the size of the query. Regarding data complexity, we prove co-NP-completeness. 1

This paper presents TRIPLE, a layered and modular rule language for the semantic web [1]. TRIPLE is based on Horn logic and borrows many basic features from F-Logic [9] but is especially designed for querying and transforming RDF models [17]. TRIPLE can be viewed as a successor of SiLRI (Simple Logic-based RDF Interpreter [5]). One of the most important dierences to F-Logic and SiLRI is that TRIPLE does not have a xed semantics for objectoriented features like classes and inheritance. Its layered architecture allows such features to be easily de- ned for dierent object-oriented and other RDF extensions like RDF Schema [16]. Description logics extensions of RDF (Schema) like OIL [14] and DAML+OIL [3] that cannot be handled directly by Horn logic are provided as modules that interact with a description logic classier, e.g. FaCT [8], resulting in a hybrid rule language. This paper sketches syntax and semantics of TRIPLE. Keywords: Semantic Web, RDF, DAML, Logic Programming, F-Logic 1

The proliferation of different standards and joint initiatives for the classification of products and services (UNSPSC, e-cl@ss, RosettaNet, NAICS, SCTG, etc.) reveals that B2B markets have not reached a consensus on coding systems, level of detail of their descriptions, granularity, etc. This paper shows how these standards and initiatives, which are built to cover different needs and functionalities, can be integrated using a common multi-layered knowledge architecture through ontological mappings. This multi-layered ontology will provide a shared understanding of the domain for applications of e-commerce, allowing information sharing and interoperation between heterogeneous systems. We will present a tool called WebPicker and a method for integrating these standards and initiatives, enriching them and obtaining the results in different formats using the WebODE platform. As an illustration, we show a case study on the computer domain, presenting the ontological mappings between UNSPSC, e-cl@ss, RosettaNet and an electronic catalogue from an e-commerce platform. 1

Motivated by the problem of automatically composing network accessible services, such as those on the World Wide Web, this paper proposes an approach to building agent technology based on the the notion of generic procedures and customizing user constraint. We argue that an augmented version of the logic programming language Golog provides a natural formalism for programming Web services. To this end, we adapt and extend the Golog language to enable programs that are generic, customizable and usable in the context of the Web. We realize these extensions in an augmented ConGolog interpreter that combines online execution of information-providing Web services with offline simulation of world-altering Web services, to determine a sequence of Web Services for subsequent execution. Our implemented system is currently interacting with services on the Web. 1

With the advent of Semantic Web languages such as OWL (Web Ontology Language), the expressive Description Logic SHOIN is exposed to a wider audience of ontology users and developers. As an increasingly large number of OWL ontologies become available on the Semantic Web and the descriptions in the ontologies become more complicated, finding the cause of errors becomes an extremely hard task even for experts. The problem is worse for newcomers to OWL who have little or no experience with DL-based knowledge representation. Existing ontology development environments, in conjunction with a reasoner, provide some limited debugging support, however this is restricted to merely reporting errors in the ontology, whereas bug diagnosis and resolution is usually left to the user. In this thesis, I present a complete end-to-end framework for explaining, pinpointing and repairing semantic defects in OWL-DL ontologies (or in other words, a SHOIN knowledge base). Semantic defects are logical contradictions that manifest as either inconsistent ontologies or unsatisfiable concepts. Where possible, I show extensions to handle related defects such as unsatisfiable roles, unintended entailments and nonentailments,

This paper presents WebODE as a workbench for ontological engineering that not only allows the collaborative edition of ontologies at the knowledge level, but also provides a scalable architecture for the development of other ontology development tools and ontology-based applications. First, we will describe the knowledge model of WebODE, which has been mainly extracted and improved from the reference model of METHONTOLOGY’s intermediate representations. Later, we will present its architecture, together with the main functionalities of the WebODE ontology editor, such as its import/export service, translation services, ontology browser, inference engine and axiom generator, and some services that have been integrated in the workbench: WebPicker, OntoMerge and the OntoCatalogue.

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This article describes PlatypusWiki, an enhanced Wiki Wiki Web using technologies from the Semantic Web. Platypus Wiki offers a simple user interface to create Wiki pages including metadata according to W3C standards. It uses RDF, RDF Schema and OWL to manage the metadata and create ontologies. We present the essential features of what we have called a Semantic Wiki Wiki Web, showing how the existing Wiki Wiki Web can be improved and how we have implemented these features in Platypus Wiki. Platypus Wiki is a rapid and useful Personal Knowledge Management system, as well as a valuable tool to manage Communities of Practice.