Decomposition - An Approach for Optimizing Queries Including ADT Functions

In order to extend the database application to CAD/CAM and other engineering areas, several systems have employed ADTs [&lo]. This extension introduces a new dimension to query optimization. Conventional query processing focuses on the cost of input and output between main and secondary memory. In contrast, to process queries involving ADT functions, the computing cost of the ADT functions must be taken into consideration, since it is often the case that they dominate the I/O cost. For example, in a chemical DBMS, to represent the structure of chemical compounds, the support of ADT “GRAPH” is necessary. Accordingly, ADT functions such as displaying a graph, calculating the number of nodes of a graph, and comparing two graphs, etc., are required. Suppose that an ADT function isomorphic is defined to determine isomorphism between two graphs. The function isomorphic is