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An important problem of OODB query optimization is to perform efficiently path traversals expressed in queries involving complex objects. Most optimizers consider a restricted search space with only traversals starting at either end of the path. In this paper, we propose a general framework for optimizing OODB queries including overlapping path traversals and explicit joins. This makes it possible to explore any traversal of a path supported by the target execution system. Furthermore, our approach enables the application of deterministic search strategies...
Declarative languages for Object-oriented DBMSs combine navigational accesses, expressed as path traversals, to associative ones. Works on query optimization for OODBs usually focus on optimizing one of the aspects (e.g., path traversals) neglecting others (e.g., associative joins). This work proposes a rule-based approach for optimizing uniformly all features encountered in queries in OODBs. Queries and rules are expressed using an easily readable functional formalism, functional symbols providing a natural way to represent both path traversals and method calls. Cost estimations are assigned to each functional equation. This enables the application of transformation rules on systems of equations under the control of deterministic cost-based search strategies, such as Iterative Improvement or Simulated Annealing...