Thesis (D.Eng.)--Chulalongkorn University, 2001

This research proposed access methods such as the direct access to terminal virtual path, the virtual path signature and the branch index for query processing of the aggregation hierarchy as a tree in object-oriented databases. The algorithm of branch generation will be proposed to generate all branches for the tree aggregation of classes in the database. For each branch, the information of linking objects is stored so that class traversal methods can be eliminated. Using a set of attribute indexes and identity indexes for each branch, associative searching can be conveniently performed. The discussion of the retrieval and update operation is performed among the access methods of aggregation hierarchy as a tree. Then, cost models in terms of storage overhead, retrieval cost and update cost are formulated. When compared with the path dictionary index formultiple paths, the result shows thatthe branch index has less storage overhead and the retrieval cost is improving in most cases. Although most of the update cost of the branch index is higher than that of the path dictionary index, it will be better than that of the path dictionary index when the update is performed on the reference between different branches.