Learn More
1 Overview With the advent of XML as a format for data exchange and semistructured databases, query languages for XML and semistructured data have become increasingly popular. Many such query languages, like XPath and XQuery, are navigational in the sense that their variable binding paradigm requires the programmer to specify path navigations through the(More)
A decade of experience with research proposals as well as standardized query languages for the conventional Web and the recent emergence of query languages for the Semantic Web call for a reconsideration of design principles for Web and Semantic Web query languages. This article first argues that a new generation of versatile Web query languages is needed(More)
Applications and services that access Web data are becoming increasingly more useful and wide-spread. Current main-stream Web query languages such as XQuery, XSLT, or SPARQL, however, focus only on one of the different data formats available on the Web. In contrast, Xcerpt is a emphversatile semi-structured query language, i.e., a query language able to(More)
We present typing rules for the Web query language Xcerpt. The rules provide a descriptive type system: the typing of a program is an approximation of its semantics. The rules can also be seen as an abstract form of a type inference algorithm (presented in previous work), and as a stage in a formal soundness proof of the algorithm. The paper considers a(More)
As XML is increasingly being used to represent information on the Web, query and reasoning languages for such data are needed. This article argues that in contrast to the navigational approach taken in particular by XPath and XQuery, a positional approach as used in the language Xcerpt is better suited for a straightforward visual representation. The(More)
Even with all the progress in Semantic technology, accessing Web data remains a challenging issue with new Web query languages and approaches appearing regularly. Yet most of these languages, including W3C approaches such as XQuery and SPARQL, do little to cope with the explosion of the data size and schemata diversity and richness on the Web. In this paper(More)
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.,(More)
Reasoning on the Web is gaining in importance because of emerging Web applications such as context-adaptive Web systems (e.g. eLearning, recommender, personalised (multi-)media, and mobile information systems), Web service retrieval and composition, and Semantic Web applications of all kinds. A central issue is combining automated reasoning methods with Web(More)
Zusammenfassung This article reports on a research project investigating the following two complementary issues: (1) improving how the structure of XML and HTML can be specified, (2) using structure specification (of XML and HTML documents) for static type checking of Web (and Semantic Web) query programs. The first step towards this goal is to provide a(More)