An Ontological Structure for Semantic Retrieval Based on Description Logics

Current information retrieval either relies on encoding process to describe given item or perform a full-text analysis to search for user-specified words. However, these syntax-based methods only reflect part of the content, so they can hardly ensure content matching. Ontology is an explicit specification of conceptualizations, which can explicitly and formally express the semantic of the concepts and their relationships. Therefore the domain ontology is better for information retrieval at semantic level. The ontological structure is determined by its specific applications. Although there are already several views on ontological structures in different contexts, the word association derived from reasoning the semantic relations between terms, the key point for semantic retrieval, has not been solved properly yet. This chapter proposes a six-element based ontological structure for semantic retrieval, and use description logic to semantically describe the atomic term, complex terms, instances, instances description, attribute assignment and axioms. Then, the new structure is evaluated by the Gruber’s criteria including explicitness and objectivity, consistency, extensibility, minimal encoding bias and minimal ontological commitment. Based on the new structure, we propose two reasoning mechanisms, i.e., terms-oriented and instances-oriented, for semantic retrieval application. Meanwhile, conversion mechanisms and determining algorithms are also proposed, which enable the reasoning for various relations in a specific area according to the rules made by domain experts. Finally, we put forward four kinds of rules for information retrieval, and analyze the applications of the new structure in semantic retrieval.