The authors propose a model, called the object request network, for representing the input requests to the optimizer which uniformly captures the main features needed in deductive and object-oriented database management systems (DBMSs). This model allows the recursive definition of derived objects, avoids some rewriting effort when changing the navigation on objects, and supports declarative request languages. The authors consider how the requests are optimized, and show that with the approach adopted it is possible to investigate more general execution plans than in earlier work.>

Object-oriented data models are being extended with recursion to gain expressive power. This complicates the optimization problem which has to deal with recursive queries on complex objects. Because unary operations invoking methods or path expressions on objects may be costly to execute, traditional heuristics for optimizing recursive queries are no longer valid. In this paper we propose a cost-based optimization method which handles object-oriented recursive queries. In particular, it is able to delay the decision of pushing selective operations through recursion until the effect of such a transformation can be measured by a cost model. The approach integrates rewriting and increases the optimization opportunities for recursive queries on objects while allowing for efficient optimization.