Query optimizers for persistent object systems should be extensible to react to user-supplied abstract types. Current architectures support only a single, non-extensible technique for controlling the optimization process. We propose an alternative to the current extensible architectures that will support multiple optimizer control strategies and the addition of new control strategies. The optimizer consists of a collection of optimization regions, each of which can transform queries according to a particular control strategy, set of transformations and cost model. A global optimizer control coordinates the movement of a query between these regions. This architecture provides extensibility in the optimizer's repertoire of control strategies through the addition of new regions. In this paper we describe our approach and demonstrate its utility by following the optimizer as it works on an example query. The optimizer will move the query between three distinct regions. The different region...

Synthesis is a complex task spanning many levels of abstractions and information domains. Hence, CAD systems utilize a global design database to achieve the much needed integration of this diverse design information into one central data model. Such a central database represents a serious bottleneck for the CAD system. First, it prevents the extensibility of the CAD system over time, since a change of the global data model requires an (often prohibitively expensive) modification of all current design tools using the database. Second, it forces all design tools to work on the same (comprehensive and hence extremely complex) data model. In this paper, we introduce a solution to this problem. We propose to utilize the object-oriented view methodology, called MultiView, for specifying customized tool interfaces (design views) on the CAD database. A design view contains a subset of relevant information from the global database organized in a fashion most suitable to the needs of a particula...