Two-level caching of composite object views of relational databases

We describe a two-level client-side cache for composite objects mapped as views of a relational database. A semantic model, the Structural Model, is used to specify joins on the relational database that are useful for defining composite objects. The lower level of the cache contains the tuples from each relation that have already been loaded into memory. These tuples are linked together from relation to relation according to the joins of the structural model. This level of the cache is shared among all applications using the data on this client. The higher level of the cache contains composed objects of data extracted from the lower level cache. This level of the cache uses the object schema of a single application, and the data is copied from the lower level cache for convenient access by the application. This two-level cache is designed as part of the Penguin system, which supports multiple applications, each with its own object schema, to share data stored in a common relational database