In this paper, we present an approach of converting XML elements into objects and store these objects into an object-oriented database (OODB). To enhance the functionality of the XML objects, attributes and methods are incorporated into XML objects. For query performance, we adopt the extended Structural Join Index Hierarchy (SJIH) mechanism as a multimedia database indexing technique. To demonstrate the validity and effectiveness of our approach, we developed a prototype multimedia application system, in which MPEG files are first processed and mapped into XML elements. Each processed XML element is then transformed into an object, with attributes and built-in methods being added into it. In this paper, we focus on retrieving MPEG objects from the OODB using SJIH mechanism, and demonstrate the validity and effectiveness of this approach through an analytical evaluation.