Semantics-based keyword search over XML and relational databases

Keyword search is a user-friendly way to retrieve information from XML and relational database (RDB). There have been many approaches proposed for keyword search over XML and RDB. However, the existing approaches cannot fully exploit hidden semantics in XML document or RDB. This causes serious problems in processing some class of keyword queries. In this paper, we thoroughly point out mismatches between answers returned by existing approaches and the expectations of common users. Through detailed analysis of these mismatches, we show the importance of semantics in keyword search over XML and RDB and propose a semantics-based approach for processing XML and RDB keyword queries. Particularly, we propose to use Object Relationship (OR) data graph and Object Relationship Mixed (ORM) data graph, which fully capture semantics of object, relationship and attribute, to represent XML document and RDB respectively, and we develop algorithms based on the proposed data model to return more comprehensive answers.