KSG – Background and need

Over the past ten to fifteen years, advances in technology have ensured that access to vast amounts of information is no longer a significant problem. Paradoxically, this abundance of information leads to the problem of information overload, making it increasingly difficult to locate relevant information. Any satisfactory solution to this problem will have to involve ways of making information machine-processable, a task which is only possible if machines have better access to the semantics of the information. It is here that ontologies play a crucial role. Roughly speaking, an ontology structures information in ways that are appropriate for a specific application domain, and in doing so, provides a way to attach meaning to the terms and relations used in describing the domain. Ontologies are widely used in applications ranging from knowledge management and natural language processing to E-health, bio-informatics, crime prevention and next-generation Web applications. A new and promising application domain for ontologies is the so-called Semantic Web, which aims for machine-understandable Web resources, whose information can then be shared and processed both by automated tools, such as search engines, and by human users.

The construction, integration, and evolution of ontologies greatly depend on the availability of ontology languages equipped with a well-defined semantics and powerful reasoning tools. Fortunately there already exists a class of logics, called description logics or DLs, that provide for both, and are therefore ideal candidates for ontology languages. That much was already clear ten years ago, but at that time, there was a fundamental mismatch between the expressive power and the efficiency of reasoning that DL systems provided, and the expressivity and the large knowledge bases that ontologists needed. Through the basic research in DLs of the last fifteen years, this gap between the needs of ontologists and the systems that DL researchers provide has finally become narrow enough to build stable bridges. In fact, the web ontology language OWL, which was accorded the status of a World Wide Web Consortium (W3C) recommendation in 2004, and is therefore the official Sermantic Web ontology language, is based on an expressive DL.