Most Semantic Web Services discovery approaches are not
well suited when using complex relational, arithmetic and logical expressions,
because they are usually based on Description Logics. Moreover,
these kind of expressions usually appear when discovery is performed including
Quality-of-Service conditions. In this work, we present an hybrid
discovery process for Semantic Web Services that takes care of QoS conditions.
Our approach splits discovery into stages, using different engines
in each one, depending on its search nature. This architecture is extensible
and loosely coupled, allowing the addition of discovery engines at
will. In order to perform QoS-aware discovery, we propose a stage that
uses Constraint Programming, that allows to use complex QoS conditions
within discovery queries. Furthermore, it is possible to obtain the
optimal offer that fulfills a given demand using this approach.Comisión Interministerial de Ciencia y Tecnología TIN2006-0047