Download RacerPro User's Guide Version 1.9.2

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CHAPTER 1. INTRODUCTION
• Find implicit subclass relationships induced by the declaration in the ontology.
• Find synonyms for resources (either classes or instance names).
• Since extensional information from OWL documents (OWL instances and their interrelationships) needs to be queried for client applications, an OWL-QL query processing
system is available as an open-source project for RacerPro.
• HTTP client for retrieving imported resources from the web. Multiple resources can
be imported into one ontology.
• Incremental query answering for information retrieval tasks (retrieve the next n results of a query). In addition, RacerPro supports the adaptive use of computational
resource: Answers which require few computational resources are delivered first, and
user applications can decide whether computing all answers is worth the effort.
Future extensions for OWL (e.g., OWL-E) are already supported by RacerPro if the system is seen as a description logic system. RacerPro already supports qualified cardinality
restrictions as an extension to OWL DL.
1.1.2
RacerPro as a Description Logic System
RacerPro is a knowledge representation system that implements a highly optimized tableau
calculus for a very expressive description logic. It offers reasoning services for multiple
T-boxes and for multiple A-boxes as well. The system implements the description logic
ALCQHI R+ also known as SHIQ (see [9]). This is the basic logic ALC augmented with
qualifying number restrictions, role hierarchies, inverse roles, and transitive roles. In addition
to these basic features, RacerPro also provides facilities for algebraic reasoning including
concrete domains for dealing with:
• min/max restrictions over the integers,
• linear polynomial (in-)equations over the reals or cardinals with order relations,
• equalities and inequalities of strings.
For these domains, no feature chains can be supported due to decidability issues.
RacerPro supports the specification of general terminological axioms. A T-box may contain general concept inclusions (GCIs), which state the subsumption relation between two
concept terms. Multiple definitions or even cyclic definitions of concepts can be handled by
RacerPro.
RacerPro implements the HTTP-based quasi-standard DIG for interconnecting DL systems
with interfaces and applications using an XML-based protocol [4]. RacerPro also implements
most of the functions specified in the older Knowledge Representation System Specification
(KRSS), for details see [17].
Given a T-box, various kinds of queries can be answered. Based on the logical semantics
of the representation language, different kinds of queries are defined as inference problems
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