Essay --

Kiryakov et.al.,(2004) have argued that semantic annotation needs to be based upon domain knowledge and not to be isolated from ontological commitments. Thus, they use ontology associations to annotate and index concepts from documents. SEWISE (Gardarin et al., 2003) uses ontologies only for describing a common data model in a given application domain that supports Web information organization and retrieval. TAP (Guha et al., 2003) represents documents and concepts are nodes using a semantic network. The main objectives of TAP are the development of a distributed query infrastructure for ontology data and augmentation of queries with data from surrounding nodes. However TAP supports only keyword search without ranking. Mayfield and Finin (2003) combine ontology-based techniques and text-based retrieval in a blind relevance feedback iteration. In their approach, taxonomies are used for query expansion, and for enhancing the semantic annotations of the documents. The documents are anno tated with the help of RDF triples, but ontology-based queries are restricted to boolean string search...