Query semi-structured for data on web

At present, the information and data on many large web are structured or semi-structured, which can be abstracted and processed similarly as relational database or objected-oriented database to raise the operation efficiency, especially the query efficiency. The Araneus data model is used, and also the link constraint, inclusion constraint and scope constraint are used. A query rewriting for semi-structured data is put forward, and this approach greatly reduces the cost of algorithm by using the knowledge of characteristic of semi-structured data and the relation between the subgoals in the query, while the soundness and completeness of algorithm are maintained.