17. The system of claim 16 , wherein, when the mashup query language normalizing module determines that the plurality of levels are linked, the data deriving module derives data corresponding to an uppermost level entity of the mashup query language from the knowledge database, derives data corresponding to consecutive lower level entities from the knowledge database based on the data corresponding to the uppermost level entity, and sequentially derives data corresponding to a lowermost level entity of the mashup query language.
18. The system of claim 17 , wherein the data deriving module derives the data corresponding to the lowermost level entity as the main information and derives the data corresponding to remaining level entities as the at least one piece of entity information.