The Ecce and Logen Partial Evaluators and their Web Interfaces

We present Ecce and Logen, two partial evaluators for Prolog using the online and offline approach respectively. We briefly present the foundations of these tools and discuss various applications. We also present new implementations of these tools, carried out in Ciao Prolog. In addition to a command-line interface new user-friendly web interfaces were developed. These enable non-expert users to specialise logic programs using a web browser, without the need for a local installation

AMaχoS—Abstract Machine for Xcerpt

Web query languages promise convenient and efficient access to Web data such as XML, RDF, or Topic Maps. Xcerpt is one such Web query language with strong emphasis on novel high-level constructs for effective and convenient query authoring, particularly tailored to versatile access to data in different Web formats such as XML or RDF. However, so far it lacks an efficient implementation to supplement the convenient language features. AMaχoS is an abstract machine implementation for Xcerpt that aims at efficiency and ease of deployment. It strictly separates compilation and execution of queries: Queries are compiled once to abstract machine code that consists in (1) a code segment with instructions for evaluating each rule and (2) a hint segment that provides the abstract machine with optimization hints derived by the query compilation. This article summarizes the motivation and principles behind AMaχoS and discusses how its current architecture realizes these principles

STARGATE : Static Repository Gateway and Toolkit. Final Project Report

STARGATE (Static Repository Gateway and Toolkit) was funded by the Joint Information Systems Committee (JISC) and is intended to demonstrate the ease of use of the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) Static Repository technology, and the potential benefits offered to publishers in making their metadata available in this way This technology offers a simpler method of participating in many information discovery services than creating fully-fledged OAI-compliant repositories. It does this by allowing the infrastructure and technical support required to participate in OAI-based services to be shifted from the data provider (the journal) to a third party and allows a single third party gateway provider to provide intermediation for many data providers (journals). Specifically, STARGATE has created a series of Static Repositories of publisher metadata provided by a selection of Library and Information Science journals. It has demonstrated the interoperability of these repositories by exposing their metadata via a Static Repository Gateway for harvesting and cross-searching by external service providers. The project has conducted a critical evaluation of the Static Repository approach in conjunction with the participating publishers and service providers. The technology works. The project has demonstrated that Static Repositories are easy to create and that the differences between fully-fledged and static OAI Repositories have no impact on the participation of small journal publishers in OAI-based services. The problems for a service that arise out of the use of Static Repositories are parallel to those created by any other repository dealing with journal articles. Problems arise from the diversity of metadata element sets provided by a given journal and the lack of specific metadata elements for the articles' volume and issue details. Another issue for the use of publishers' metadata arise as the collection policies of some existing services only allow Open Access materials to be included in them. The project recommends that the use of Static Repositories continues to be explored - in particular as a flexible way to expose existing sets of structured information to OAI services and to create the opportunity to enhance the metadata as part of the process. The project further recommends that the publishing community consider the creation or adoption of an application profile for journal articles to support information discovery that can search by volume and issue. Significant further use of the Static Repository technology by small journal publishers will require the future creation and maintenance of a community-specific Static Repository Gateway. Further use will also require advocacy within the publishing community but might initially be most effectively kick-started through the creation of OAI repositories based on metadata held by the commercial services which publish or mediate access to electronic copies of journals on behalf of small publishers

A Taxonomy of Workflow Management Systems for Grid Computing

With the advent of Grid and application technologies, scientists and engineers are building more and more complex applications to manage and process large data sets, and execute scientific experiments on distributed resources. Such application scenarios require means for composing and executing complex workflows. Therefore, many efforts have been made towards the development of workflow management systems for Grid computing. In this paper, we propose a taxonomy that characterizes and classifies various approaches for building and executing workflows on Grids. We also survey several representative Grid workflow systems developed by various projects world-wide to demonstrate the comprehensiveness of the taxonomy. The taxonomy not only highlights the design and engineering similarities and differences of state-of-the-art in Grid workflow systems, but also identifies the areas that need further research.Comment: 29 pages, 15 figure

Rewrite based Verification of XML Updates

We consider problems of access control for update of XML documents. In the context of XML programming, types can be viewed as hedge automata, and static type checking amounts to verify that a program always converts valid source documents into also valid output documents. Given a set of update operations we are particularly interested by checking safety properties such as preservation of document types along any sequence of updates. We are also interested by the related policy consistency problem, that is detecting whether a sequence of authorized operations can simulate a forbidden one. We reduce these questions to type checking problems, solved by computing variants of hedge automata characterizing the set of ancestors and descendants of the initial document type for the closure of parameterized rewrite rules

Projector - a partially typed language for querying XML

We describe Projector, a language that can be used to perform a mixture of typed and untyped computation against data represented in XML. For some problems, notably when the data is unstructured or semistructured, the most desirable programming model is against the tree structure underlying the document. When this tree structure has been used to model regular data structures, then these regular structures themselves are a more desirable programming model. The language Projector, described here in outline, gives both models within a single partially typed algebra and is well suited for hybrid applications, for example when fragments of a known structure are embedded in a document whose overall structure is unknown. Projector is an extension of ECMA-262 (aka JavaScript), and therefore inherits an untyped DOM interface. To this has been added some static typing and a dynamic projection primitive, which can be used to assert the presence of a regular structure modelled within the XML. If this structure does exist, the data is extracted and presented as a typed value within the programming language