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Proposal - start [kondor.etf.rs]

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Figure 10. Rough timeline vision of the concept-searching evolution from 1960 till 2010.<br />

Three types of concept-base search systems are presented next: KeyConcept, the Automated<br />

Generated Thesaurus Approach, and the Semantic Web.<br />

2.3.1. KeyConcept<br />

An example of a concept-based retrieval engine is KeyConcept [GAUCH 2002]. There,<br />

concepts are fi<strong>rs</strong>t processed by a traditional indexer using training documents under a tf.idf<br />

indexing method (Figure 11). The outputs of the tf.idf method are concepts where each<br />

concept is presented as a centroid of the training set of documents for the observed concept.<br />

Figure 11. The tf.itf indexing method.<br />

The conceptual indexer of KeyConcept processes new (non training) documents by using a<br />

Vector Space Model (VSM) [SALTON 1975]. Concept-based retrieval is done by processing<br />

similarity level values obtained from VSM, words/concepts and an L-factor (entered by the<br />

user). The KeyConcept system architecture is presented in Figure 12.

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