Section: Software

XML Reasoning Solver

Participants : Pierre Genevès, Nabil Layaïda, Nils Gesbert, Manh-Toan Nguyen.

The XML Reasoning Solver is a tool for the static analysis of XPath queries and XML schemas based on the latest theoretical advances. It allows automated verification of properties that are expressed as logical formulas over trees. A logical formula may for instance express structural constraints or navigation properties (like e.g. path existence and node selection) in finite trees.

The tool can solve many fundamental XML problems such as satisfiability of XPath expressions in the presence of XML schemas, containment and equivalence of XPath expressions, and many other problems that can be formulated with XPath expressions and schemas (DTDs, XML Schemas, Relax-NG).

The system is implemented in Java and uses symbolic techniques (binary decision diagrams) in order to enhance its performance. It is capable of comparing path expressions in the presence of real-world DTDs (such as the W3C SMIL and XHTML language recommendations, for instance). The cost ranges from several milliseconds for comparison of XPath queries without tree types, to several seconds for queries under very large, heavily recursive, type constraints, such as the XHTML DTD. These measurements shed light for the first time on the cost of solving static analysis problems in practice. Furthermore, the analyzer generates XML counter-examples that allow program defects to be reproduced independently from the analyzer.

Extensions for CSS

We have introduced the first system capable of statically verifying properties of a given cascading style sheet (CSS) over the whole set of documents to which this stylesheet applies [5] . The system is composed of a set of parsers for reading the CSS and schema files (XML Schema, Relax NG, or DTD) together with a text file corresponding to problem description as a logical formula. We have developed a compiler that translates CSS files into their logical representations. Then, the solver takes the overall problem formulation and checks it for satisfiability.

XQuery IDE

We have started the development of an XQuery IDE with a web interface. This prototype integrates static analyses performed by the solver inside a development environment suited for XQuery programmers.