Semantic Query Formulation and Evaluation for XML Databases

A semantic query attempts to help a user to obtain or manipulate data in a database without knowing its detailed syntactic structure. Formulation and evaluation of semantic queries require schematic and other constraint information as well as general domain knowledge. A new approach to the formulation and evaluation of semantic queries for XML databases is proposed. It employs XML Declarative Description (XDD)—an XML based knowledge representation—to model the databases together with the schemata of their XML elements and to represent domain knowledge resulting in a uniform representation of all the required information. Equivalent Transformation (ET)—a new computation paradigm which transform a representation into another one while preserving their meanings—is used to optimize and evaluate the queries.