Jan Maluszynski - Böcker

The Semantic Web is a major endeavor aimed at enriching the existing Web withmetadataandprocessingmethodssoastoprovideWeb-basedsystemswith advanced(so-calledintelligent)capabilities,inparticularwithcontext-awareness and decision support. The advanced capabilities striven for in most Semantic Web application s- narios primarily call for reasoning. Reasoning capabilities are o?ered by exi- ing Semantic Web languages, such as BPEL4WS, BPML, ConsVISor, DAML-S, JTP, TRIPLE, and others. These languages, however, were developed mostly from functionality-centered (e.g., ontology reasoning or access validation) or application-centered (e.g., Web service retrieval and composition) perspectives. A perspective centered on the reasoning techniques (e.g., forward or backward chaining, tableau-like methods, constraint reasoning, etc.) complementing the above-mentioned activities appears desirable for Semantic Web systems and - plications. The workshop on "Principles and Practice of Semantic Web Reas- ing," which took place on December 8, 2003, in Mumbai, India, was the ?rst of a series of scienti?c meetings devoted to such a perspective.JustasthecurrentWebisinherentlyheterogeneousindataformatsanddata semantics, the Semantic Web will be inherently heterogeneous in its reasoning forms.Indeed,anysingleformof reasoningturnsouttobeirrealin theSemantic Web. For example, ontology reasoning in general relies on monotonic negation (for the metadata often can be fully speci?ed), while databases, Web databases, and Web-based information systems call for non-monotonic reasoning (for one would not specify non-existing trains in a railway timetable); constraint reas- ing is needed when dealing with time (for time intervals have to be dealt with), while(forwardand/orbackward)chainingisthereasoningofchoicewhencoping with database-like views (for views, i.e., virtual data, can be derived from actual data using operations such as join and projections).

This volume contains the tutorial papers of the Summer School “Reasoning Web,”July25–29,2005(http://reasoningweb. org). TheSchoolwashostedbythe University of Malta and was organized by the Network of Excellence REWERSE “Reasoning on the Web with Rules and Semantics” (http://rewerse. net), funded by the EU Commission and by the Swiss Federal O?ce for Edu- tion and Science within the 6th Framework Programme under the project ref- ence number 506779. The objective of the school was to provide an introduction into methods and issues of the Semantic Web, a major endeavor in current Web research, where the World Wide Web Consortium W3C plays an important role. The main idea of the Semantic Web is to enrich Web data with meta-data carrying a “meaning” of the data and allowing Web-based systems to reason about data (and meta-data). The meta-data used in Semantic Web applications is usually linked to a conceptualization of the application domain shared by di?erent applications. Such a conceptualization is called an ontology and sp- i?es classes of objects and relations between them. Ontologies are de?ned by ontology languages, based on logic and supporting formal reasoning. Just as the current Web is inherently heterogeneous in data formats and data semantics, the Semantic Web will be inherently heterogeneous in its reasoning forms. - deed, any single form of reasoning turns out to be insu?cient in the Semantic Web.

The aim of the workshop was to discuss whether research on implementation of programming languages and research on logic programming can mutually benefit from each others results. The intention was to bring together researchers from both fields, especially those working in the area of their intersection. Problems such as formal specification of compilers and syntax-based editors, program analysis and program optimization have been traditionally studied by implementors of algorithmic languages and have resulted in a number of well-established notions, formalisms and techniques. At the same time, an increasing number of people use logic programming as a way of specifying compilers or other programming environment tools, taking advantage of the relatively high level of logic programming and the growing efficiency of Prolog implementations. On the other hand, research on logic programming raises the questions of analysis of logic programs and their optimization. These are motivated primarily by compiler construction for logic programs, by studies on the methodology of logic programming and by the attempts to amalgamate logic programming and functional programming. The purpose of the workshop is to review the techniques developed in one (or both) of the fields which could also be of some help in the other one and to facilitate the transfer of expertise. It seems important to compare notions used in both fields: showing similarities between them may prevent rediscovering results already known, while studying differences may contribute to the transfer of technology.

This volume consists of the papers accepted for presentation at the second international workshop on Programming Language Implementation and Logic Programming (PLILP '90) held in Linköping, Sweden, August 20-22, 1990. The aim of the workshop was to identify concepts and techniques used both in implementation of programming languages, regardless of the underlying programming paradigm, and in logic programming. The intention was to bring together researchers working in these fields. The volume includes 26 selected papers falling into two categories. Papers in the first category present certain ideas from the point of view of a particular class of programming languages, or even a particular language. The ideas presented seem to be applicable in other classes of languages. Papers in the second category directly address the problem of integration of various programming paradigms. The proceedings of the predecessor workshop PLILP '88, held in Orléans, France, May 16-18, 1988, are available as Lecture Notes in Computer Science, Vol. 348.

This volume contains the papers which have been accepted forpresentation atthe Third International Symposium onProgramming Language Implementation andLogic Programming(PLILP '91) held in Passau, Germany, August 26-28, 1991. Theaim of the symposium was to explore new declarativeconcepts, methods and techniques relevant for theimplementation of all kinds of programming languages,whether algorithmic or declarative ones. The intention wasto gather researchers from the fields of algorithmicprogramming languages as well as logic, functional andobject-oriented programming. This volume contains the twoinvited talks given at the symposium by H. Ait-Kaci and D.B. MacQueen, 32 selected papers, and abstracts of severalsystem demonstrations. The proceedings of PLILP '88 andPLILP '90 are available as Lecture Notes in Computer ScienceVolumes 348 and 456.

The Reasoning Web summer school series is a well-established event, attracting experts from academia and industry as well as PhD students interested in fo- dational and applicational aspects of the Semantic Web. This volume contains thelecturenotesofthefourthsummerschool, which took place in Venice, Italy, in September 2008. This year, the school focussed on a number of important application domains, in which semantic web techniques have proved to be p- ticularly e?ective or promising in tackling problems. The ?rst three chapters provide introductory material to: - languages, formalisms, and standards adopted to encode semantic information; - "soft" extensions that might be useful in contexts such as multimedia or social network applications; - controlled natural language techniques to bring ontology authoring closer to end users. The remaining chapters cover major application areas such as social networks, semantic multimedia indexing and retrieval, bioinformatics, and semantic web services.Thepresentationshighlightedwhichtechniquesarealreadybeingsuccessfully applied for purposes such as improving the performance of information retrieval algorithms,enablingtheinteroperationofheterogeneousagents,modellinguser's pro?les and social relations, and standardizing and improving the accuracy of very large and dynamic scienti?c databases. Furthermore, the lectures pointed out which aspects are still waiting for a solution,andthepossiblerolethatsemantictechniquesmayplay,especiallythose reasoningmethodsthathavenotyetbeenexploitedtotheirfullpotential.Wehope thatthe school'smaterialwillinspire further exciting researchinthese areas. We are grateful to all the lecturers and their co-authors for their excellent contributions, to the Reasoning Web School Board, and Norbert Eisinger in particular, who helped in several critical phases, and to the organizations that supported this event: the University of Padua, the MOST project, and the N- work of Excellence REWERSE.