OR tree representation should be suitable only for
architectures of less resource. It describes resource usage
clearly, but it obviously requires much more space and the
seraching does not consider the previous searching result.

AND-OR tree representation solves the problems and it is
easy to be expandded. The problem comes with those unflexible
architecture. For example, the architectur has 2 WR ports.
1 WR port is accessible from a particular memory unit. The
other one is available to all memory units. A pure AND-OR
tree can not represent it. We need certain kind of checking
rule modification.

Shaojie Wang