Metadata is considered a very useful and valuable component in handing data and delivering decisional information, in managing contents on the Internet, in databases and warehouses, in enabling the finding of relevant information, and in effectively providing a multiplicity of useful services. Data, in point of facts, can be metaphorically compared to a dead substance; and all acknowledge the fact that data, by merely existing in systems, represents almost nothing. However, it is the awareness of the exact length and value of this data that builds the valuable expensive information. This thesis ...