Julian Seidenberg

Web ontology segmentation: analysis, classification and use

Ontologies are at the heart of the semantic web. They define the concepts and relationships that make global interoperability possible. However, as these ontologies grow in size they become more and more difficult to create, use, understand, maintain, transform and classify. We present and evaluate several algorithms for extracting relevant segments out of large description logic ontologies for the purposes of increasing tractability for both humans and computers. The segments are not mere fragments, but stand alone as ontologies in their own right. This technique takes advantage of the detailed semantics captured within an OWL ontology to produce highly relevant segments. The research was evaluated using the GALEN ontology of medical terms and procedures.

Web Ontology Segmentation: Extraction, Transformation, Evaluation

In this chapter we present an algorithm for extracting relevant segments out of large description logic ontologies for the purposes of increasing tractability for both humans and computers. We offer several variations on this algorithm for different purposes. The segments are not mere fragments, but stand alone as ontologies in their own right. This technique takes advantage of the detailed semantics captured within an OWL ontology to produce highly relevant segments. However, extracted segments make no guarantee for preserving the semantics of the complete ontology.

Representing transitive propagation in OWL

Transitive propagation along properties can be modelled in various ways in the OWL description logic. Doing so allows existing description logic reasoners based on the tableaux algorithm to make inferences based on such transitive constructs. This is espectially useful for medical knowledge bases, where such constructs are common. This paper compares, contrasts and evaluates a variety of different methods for simulating transitive propagation: property subsumption, classic SEP triples and adapted SEP triples. These modelling techniques remove the need to extending the OWL language with additional operators in order to express the transitive propagation. Other approaches require an extended tableaux reasoner or first-order logic prover, as well as a modification of the OWL standard. The adapted SEP triples methodology is ultimately recommended as the most reliable modelling technique.

A methodology for asynchronous multi-user editing of semantic web ontologies

Current tools, techniques and methodologies for multi-user editing of semantic web ontologies are inadequate. The vast majority of ontologies are maintained by single individuals. However, single user access is increasingly becoming a bottleneck as these ontologies grow in size. We therefore suggest a technique and for locking segments of description logic ontologies for multi-user editing. This technique fits into a methodology for ontology editing in which multiple ontology engineers concurrently lock, extract, modify, error-check and re-merge individual segments of a large ontology. The technique aims to provide a pragmatic compromise between a very restrictive approach that might offer complete error protection but make useful multi-user interactions impossible and a wide-open anything-goes editing paradigm which offers little to no protection.