**1. Introduction**

80 Semantics – Advances in Theories and Mathematical Models

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Semantic caching (Ren, Q et al., 2003),(Dar et al., 1996) is said to be a technique for storing data and their corresponding semantic descriptions. Concept of semantic cache itself is quite simple but the reasoning required to evaluate any query over a semantic cache can be very complex (Godfrey P. and Gryz J., 1997). The reasoning over stored semantics is a determination process to know how query and cache formulas are related semantically. This reasoning is termed as semantic cache query processing (Ren, Q et al., 2003),(Dar et al., 1996). In this chapter we demonstrate several semantic cache query processing techniques for relational queries, web queries, xml queries, answering queries form materialized views and logic based subsumption analysis queries.

Mainly there are two types of semantic query processing approaches, structured-semantics and unstructured-semantics. In structured-semantics original problem or query is represented in a structure that has the ability to contain semantics along with its structure. Examples of structured-semantics are ontology, resource description framework (RDF) and extensible markup language (XML) etc. Unstructured-semantics approaches perform reasoning for semantic extraction from structures that do not posses semantics in their representations. Semantic cache query processing is an example of unstructured-semantics reasoning. Since standard query language (SQL) is structured but it do not contains semantics of data to be answered against a query and query itself.

In this chapter we demonstrate several semantic cache reasoners for unstructuredsemantics. All of these semantic cache reasoning techniques represent query language to a mediate structured-semantic representation for semantic extraction.
