Towards Semantic Query Optimization for XML Databases

The proposed semantic query optimization framework employs XML Equivalent Transformation Rules (XET rules) as a primary mechanism to transform given queries into semantically equivalent forms that are more efficient. XET rules are prepared from semantic knowledge of databases represented by XML Integrity Constraints. Their applications in the query transformation process are effectively guided by a two-phase heuristic-based optimization strategy and a condition-part-based control strategy.