Sebastian Schaffert, François Bry, Tim Furche, Benedikt Linse, Andreas Schroeder:
Tim Furche (editor):
Refinement of Principles of the Xcerpt Processors.

Complete Text [
.pdf, 3.07MB]
In: (I4-D11)

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 differentWeb formats such as XML or RDF. However, so far it lacks an efficient implementation to supplement the convenient language features. AMAcOS is an abstract machine implementation for Xcerpt that aims at efficiency and ease of deployment. The first part of this deliverable summarizes the motivation and principles behind AMAcOS and discusses how its current architecture realizes these principles. The second part of this deliverable describes the operational semantics of the Xcerpt prototype. The operational semantics consists of three parts: the description of the constraint solver, the definition of simulation unification, and the description of the (backward) chaining in the prototype. The simulation unification is the core concept of the Xcerpt prototype, unique among Web query and logic languages.



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