Survey over Existing Query and Transformation Languages

A widely acknowledged obstacle for realizing the vision of the Semantic Web is the inability of many current Semantic Web approaches to cope with data available in such diverging representation formalisms as XML, RDF, or Topic Maps. A common query language is the first step to allow transparent access to data in any of these formats. To further the understanding of the requirements and approaches proposed for query languages in the conventional as well as the Semantic Web, this report surveys a large number of query languages for accessing XML, RDF, or Topic Maps. This is the first systematic survey to consider query languages from all these areas. From the detailed survey of these query languages, a common classification scheme is derived that is useful for understanding and differentiating languages within and among all three areas

Towards a Rule Interchange Language for the Web

This articles discusses rule languages that are needed for a a full deployment of the SemanticWeb. First, it motivates the need for such languages. Then, it presents ten theses addressing (1) the rule and/or logic languages needed on the Web, (2) data and data processing, (3) semantics, and (4) engineering and rendering issues. Finally, it discusses two options that might be chosen in designing a Rule Interchange Format for the Web

Web and Semantic Web Query Languages

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

Metadatenverwaltung für Multimedia-Content-Management mit OLAP-Funktionalität

Der Hauptschwerpunkt bei der Entwicklung wireless-orientierter, multimedialer Content- Management-Systeme liegt auf der adäquaten Speicherung, Verwaltung und Recherche multimedialer Dokument-Strukturen sowie auf der anwendungsspezifischen Darstellung und Repräsentation dieser Dokumente auf verschiedenen Endgeräten. In diesem Kontext kann die Extensible Markup Language (XML) zur Verbesserung einer großen Bandbreite möglicher Anwendungen beitragen. Im Rahmen dieser Arbeit wird ein Ansatz für eine universelle Metadatenverwaltung zur Steuerung signifikanter Transformations - und Daten-Analyse-Prozesse entwickelt. Dabei wird eine möglichst enge Kopplung von Data Warehouse-Funktionalität (OLAP) mit einer ausgewählten XML-Framework-Architektur angestrebt. Ziel ist ein erweiterter Architektur-Vorschlag, der die Grundlage für zukünftige offene und erweiterbare Multimedia-Content-Management-Systeme bilden kann. Grundlage dieser Architektur ist ein Metadaten-Repository auf der Basis der Resource Description Framework Spezifikation (RDF)

Identification of Design Principles

This report identifies those design principles for a (possibly new) query and transformation language for the Web supporting inference that are considered essential. Based upon these design principles an initial strawman is selected. Scenarios for querying the Semantic Web illustrate the design principles and their reflection in the initial strawman, i.e., a first draft of the query language to be designed and implemented by the REWERSE working group I4

Multivalent Metadata : Exploiting the Layers of Meaning in Digital Resources

The rapid growth of the World Wide Web was due in part to the simplicity of the Hypertext Markup Language (HTML). It is anticipated that the next generation of web technology, coined the Semantic Web, by Tim Berners-Lee (1989, p. 1), will be driven by the Extensible Markup Language (XML). The XML suite of technologies provides a framework for the application of metadata, and hence semantic information, to web resources. Advantages of a semantic web include improved sharing and reuse of resources, enhanced search mechanisms and knowledge management. The knowledge or meaning contained in digital information may vary according to the perspective of the viewer and can be seen therefore as multivalent in nature. Semantic information that is highly relevant to one user may be of no interest to another. The aim of this project was to demonstrate the layers of meaning inherent in a data sample and how they could be encapsulated in metadata then accessed and manipulated using current technologies, thus leveraging the knowledge contained. Analysis of the data sample, a typical component of an online training product, determined meaningful ways in which the knowledge contained could be reused and adapted. From this analysis a set of test criteria was generated. Metadata was then created for the sample data and the tests implemented using a range of XML technologies

Our data - our responsibility: the semantic web, deep linking and repositories

The paper examines some possibilities in terms of adapting roles and responsibilities to further ensure that content, and the correct associated metadata, as provided through repositories, are discoverable. It is proposed that the key roles affected would be those of the subject specialists (subject librarians), the metadata specialists, repository managers, and as importantly, the authors and publishers at these institutions. Using the Ichthyological Bulletin series (as published by Rhodes University between 1956 and 2001), deep-linking options will be examined, as well as the challenges experienced pertaining to data linking as part of this specific digitization project

Data Integration on the (Semantic) Web with Rules and Rich Unification

For the last decade a multitude of new data formats for the World Wide Web have been developed, and a huge amount of heterogeneous semi-structured data is flourishing online. With the ever increasing number of documents on the Web, rules have been identified as the means of choice for reasoning about this data, transforming and integrating it. Query languages such as SPARQL and rule languages such as Xcerpt use compound queries that are matched or unified with semi-structured data. This notion of unification is different from the one that is known from logic programming engines in that it (i) provides constructs that allow queries to be incomplete in several ways (ii) in that variables may have different types, (iii) in that it results in sets of substitutions for the variables in the query instead of a single substitution and (iv) in that subsumption between queries is much harder to decide than in logic programming. This thesis abstracts from Xcerpt query term simulation, SPARQL graph pattern matching and XPath XML document matching, and shows that all of them can be considered as a form of rich unification. Given a set of mappings between substitution sets of different languages, this abstraction opens up the possibility for format-versatile querying, i.e. combination of queries in different formats, or transformation of one format into another format within a single rule. To show the superiority of this approach, this thesis introduces an extension of Xcerpt called Xcrdf, and describes use-cases for the combined querying and integration of RDF and XML data. With XML being the predominant Web format, and RDF the predominant Semantic Web format, Xcrdf extends Xcerpt by a set of RDF query terms and construct terms, including query primitives for RDF containers collections and reifications. Moreover, Xcrdf includes an RDF path query language called RPL that is more expressive than previously proposed polynomial-time RDF path query languages, but can still be evaluated in polynomial time combined complexity. Besides the introduction of this framework for data integration based on rich unification, this thesis extends the theoretical knowledge about Xcerpt in several ways: We show that Xcerpt simulation unification is decidable, and give complexity bounds for subsumption in several fragments of Xcerpt query terms. The proof is based on a set of subsumption monotone query term transformations, and is only feasible because of the injectivity requirement on subterms of Xcerpt queries. The proof gives rise to an algorithm for deciding Xcerpt query term simulation. Moreover, we give a semantics to locally and weakly stratified Xcerpt programs, but this semantics is applicable not only to Xcerpt, but to any rule language with rich unification, including multi-rule SPARQL programs. Finally, we show how Xcerpt grouping stratification can be reduced to Xcerpt negation stratification, thereby also introducing the notion of local grouping stratification and weak grouping stratification