Property of separability in physical design of network model databases

We present a physical design methodology for network model databases based on the theory of separability. In particular, we present a cost model and a usage specification scheme that are suitable for describing the network model database environment. We subsequently prove that, under these usage and cost models, a large subset of practically important access structures that are available in network model database systems satisfies the conditions for separability. The theory of separability was introduced in an earlier work, in the context of relational systems, as a formal basis for partitioning the problem of designing the optimal physical database. The theory proves that, given a certain set of access structures and a usage specification scheme, the problem of optimal assignment of access structures to the entire database can be reduced to the subproblem of optimizing individual record types independently of one another. The approach we present significantly reduces the complexity of the design problem which has the potential of being combinatorially explosive. A heuristic extension of the formal methodology to the access structures not incorporated in the theory is also discussed.