We study structural properties of each of the mainsublanguages of XPath [8] commonly used in practice.First, we characterize the expressive power of these lan-guage fragments in terms of both logics and tree pat-terns. Second, we investigate closure properties, fo-cusing on the ability to perform basic Boolean oper-ations while remaining within the fragment. We give a<lb...

Extracting search result records (SRRs) from webpages is useful for building an aggregated search engine which combines search results from a variety of search engines. Most automatic approaches to search result extraction are not portable: the complete process has to be rerun on a new search result page. In this paper we describe an algorithm to automatically determine XPath expressions to ext...

The ubiquitous adoption of XML as the standard of data exchange over the web has led to increased interest in building efficient and scalable XML publish-subscribe (pub-sub) systems. The central function of an XML-based pub-sub system is to perform XML filtering efficiently, i.e. identify those XPath expressions that have a match in a streaming XML document. In this paper, we propose a new sequ...

Geography Markup Language (GML) has been established as the standard language for the transport, storage and modelling of geographic information. In this paper we study how to adapt the XPath query language to GML documents. With this aim, we have defined a XPath based query language which handles the “semantic structure” of GML. Our approach focuses on querying urban maps whose representation ...

Querying data from presentation formats like HTML, for purposes such as information extraction, requires the consideration of tree structures as well as the consideration of spatial relationships between laid out elements. The underlying rationale is that frequently the rendering of tree structures is very involved and undergoing more frequent updates than the resulting layout structure. Theref...

Functional Dependencies (FDs) are a common constraint for many applications. Specifying FDs in XML documents, however, is difficult because XML documents do not have uniform structures. We introduce XML Template Functional Dependencies (XTFDs), which can specify FDs in XML documents, in this paper. Previously, we defined XTFDs in terms of variables only (Mok, 2005). In this paper, we extend our...

Consider XML content-based document routing: a stream of XML documents are routed through a network, and routing decisions are taken based on the result of evaluating XPath predicates on these documents. Parsing XML documents and interpreting XPath expressions is the main bottleneck in such systems. We propose a novel solution to speedup the evaluation of XPath predicates based on precomputing ...

A common task that is often needed in many software development tools is the capability to search the artifact that is being created in a flexible and efficient manner. However, this capability is typically absent in meta-programmable modeling tools, which can be a serious disadvantage as the size of a model increases. As a remedy, we introduce a method to search domain models using XPath – a W...