Catálogo de publicaciones - libros

The aim of this chapter is to give a general introduction to some of the ontology languages that play a prominent role on the Semantic Web, and to discuss the formal foundations of these languages. Web ontology languages will be the main carriers of the information that we will want to share and integrate.

F-logic is a formalism that integrates logic with object-oriented programming in a clean and declarative fashion. It has been successfully used for information integration, ontology modeling, agent-based systems, software engineering, and more. This paper gives a brief overview of F-logic and discusses its features from the point of view of an ontology language.

A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web query languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of languages falling into these categories and summarises their salient aspects. The languages are introduced using common sample data and query types. Key aspects of the query languages considered are stressed in a conclusion.

The Web and the Semantic Web, as we see it, can be understood as a “living organism” combining autonomously evolving data sources, each of them possibly reacting to events it perceives. Rather than a Web of data sources, we envisage a Web of Information Systems, where each such system, besides being capable of gathering information (querying persistent data, as well as “listening” to volatile data such as occurring events), is capable of updating persistent data, communicating the changes, requesting changes of persistent data in other systems, and being able to react to requests from other systems. The dynamic character of such a Web requires declarative languages and mechanisms for specifying the evolution of the data. In this course we will talk about foundations of evolution and reactive languages in general, and will then concentrate on some specific issues posed by evolution and reactivity in the Web and in the Semantic Web.

Searching for the meaning of the word “personalization” on a popular search engine, one finds twenty-three different answers, including “the process of matching categorized content with different end users based on business rules ... upon page request to a Webserver” , “using continually adjusted user profiles to match content or services to individuals” , and also “real-time tailoring of displays, particularly Web pages, to a specific customer’s known preferences, such as previous purchases” . A little more generally, personalization is a process by which it is possible to give the user optimal support in accessing, retrieving, and storing information, where solutions are built so as to fit the preferences, the characteristics and the taste of the individual. This result can be achieved only by exploiting machine-interpretable semantic information, e.g. about the possible resources, about the user him/herself, about the context, about the goal of the interaction. Personalization is realized by an inferencing process applied to the semantic information, which can be carried out in many different ways depending on the specific task. The objective of this paper is to provide a coherent introduction into issues and methods for realizing personalization in the Semantic Web.

Attempto Controlled English (ACE) is a knowledge representation language with an English syntax. Thus ACE can be used by anyone, even without being familiar with formal notations. The Attempto Parsing Engine translates ACE texts into discourse representation structures, a variant of first-order logic. Hence, ACE turns out to be a logic language equivalent to full first-order logic. The two views of ACE — natural language and logic language — complement each other, and render ACE both human- and machine-readable. This paper covers both views of ACE. In the first part we present the language ACE in a nutshell, and in the second part we give an overview of the discourse representation structures derived from ACE texts.

In this paper we address several issues of rule modeling on the basis of UML. We discuss the relationship between UML class models and OWL vocabularies. We show how certain rules can be specified in a class diagram with the help of OCL. We also show how rule concepts can be described, and how the abstract syntax of RDF, OWL, SWRL and RuleML can be defined, by means of UML class diagrams in a concise way.

The World Wide Web represents a universe of knowledge and information. Unfortunately, it is not straightforward to query and access the desired information. Languages and tools for accessing, extracting, transforming, and syndicating the desired information are required. The Web should be useful not merely for human consumption but additionally for machine communication. Therefore, powerful and user-friendly tools based on expressive languages for extracting and integrating information from various different Web sources, or in general, various heterogeneous sources are needed. The tutorial gives an introduction to Web technologies required in this context, and presents various approaches and techniques used in information extraction and integration. Moreover, sample applications in various domains motivate the discussed topics and providing data instances for the Semantic Web is illustrated.

Applications using semantic technology are not fundamentally different from other software products. As standard applications, they need a well-defined development process, an appropriate modelling technology, and, to decrease construction cost, a good reuse technology for models and components. This paper shows that employing ontologies can help to enlarge the reuse factor. Ontologies improve the refinement process in object-oriented software development, simplify design of product lines, improve interoperability in component-based systems, and help in service-based applications, such as web services. Hence, ontologies will play an important role in the future engineering of software products.

Various schema languages have been introduced to describe (classes of) Web documents (DTD, XML Schema, Relax NG). We present mathematical treatment of their main features. We are interested in the sets of documents a schema defines; such sets will be called types. Using a mathematical formalism makes it possible to discuss chosen aspects of a schema language in a precise and simple way. Otherwise they are hidden among numerous details of a large and sophisticated schema language. Our goal is typing of rule languages, more precisely approximately describing their semantics by means of types. Thus we are interested in formalisms for types that facilitate constructing (efficient) algorithms performing those operations on types that are needed in type checking and type inference for rules.