A Generic Module System forWeb Rule Languages: Divide and Rule

An essential feature in practically usable programming languages is the ability to encapsulate functionality in reusable modules. Modules make large scale projects tractable by humans. For Web and Semantic Web programming, many rule-based languages, e.g. XSLT, CSS, Xcerpt, SWRL, SPARQL, and RIF Core, have evolved or are currently evolving. Rules are easy to comprehend and specify, even for non-technical users, e.g. business managers, hence easing the contributions to the Web. Unfortunately, those contributions are arguably doomed to exist in isolation as most rule languages are conceived without modularity, hence without an easy mechanism for integration and reuse. In this paper a generic module system applicable to many rule languages is presented. We demonstrate and apply our generic module system to a Datalog-like rule language, close in spirit to RIF Core. The language is gently introduced along the EU-Rent use case. Using the Reuseware Composition Framework, the module system for a concrete language can be achieved almost for free, if it adheres to the formal notions introduced in this paper

Rule Interchange on the Web

Abstract. Rules play an increasingly important role in a variety of Semantic Web applications as well as in traditional IT systems. As a universal medium for publishing information, the Web is envisioned to become the place for publishing, distributing, and exchanging rule-based knowledge. Realizing the importance and the promise of this vision, W3C has created the Rule Interchange Format Working Group (RIF WG) and chartered it to develop an interchange format for rules in alignment with the existing standards in the Semantic Web architecture stack. However, creating a generally accepted interchange format is by no means a trivial task. First, there are different understandings of what a “rule ” is. Researchers and practitioners distinguish between deduction rules, normative rules, production rules, reactive rules, etc. Second, even within the same category of rules, systems use different (often incompatible) semantics and syntaxes. Third, existing Semantic Web standards, such as RDF and OWL, show incompatibilities with many kinds of rule languages at a conceptual level. This article discusses the role that different kinds of rule languages and systems play on the Web, illustrates the problems and opportunities in exchanging rules through a standardized format, and provides a snapshot of the current work of the W3C RIF WG. 2 Boley et al.

Evolution of distributed Web data: An application of the reactive language XChange

Many data sources on the Web evolve in the sense that they change their content over time, typically as a reaction to some event. Such changes often need to be mirrored in data on other Web nodes: updates need to be propagated. To respond to the need for evolution and reactivity both locally and globally, the language XChange has been developed. In this work, we demonstrate its applicability to a concrete scenario of distributed Web sites of a scientific community with mutual data dependencies. 1

Abstract

Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events

Rich Clients need Rich Interfaces Query Languages for XML and RDF Access on the Web

Abstract—Access to Web data has become an integral part of many applications and services. In the past, such data has usually been accessed throughhuman-tailoredHTMLinterfaces.Nowadays,richclientinterfaces in desktop applications or, increasingly, in browser-based clients ease data access and allow more complex client processing based on XML or RDF data retrievedthrough Webservice interfaces.Convenient speci�cationsof the data processing on the client and �exible, expressive service interfaces for data access become essential in this context. Web query languages such as XQuery, XSLT, SPARQL, or Xcerpt have been tailored speci�cally for such a setting: declarative and e�cient access and processing of Web data. �is tutorial introduces, compares, and classi�es the most relevant exemplars of Web query languages for XML, RDF, and/or TopicMaps data. Interesting features as well as di�erences in expressiveness and adequacy are digested along practical and concrete use cases. Emphasis is placed on recent W3C standardization activities, contrasted with alternativ