Querying an Object-Oriented Database Using CPL

The Collection Programming Language is based on a complex value model of data and has successfully been used for querying transforming and integrating data from a wide variety of structured data sources - relational, ACeDB, and ASN.1 among others. However, since there is no notion of objects and classes in CPL, it cannot adequately model recursive types or inheritance, and hence cannot be used to query object-oriented databases (OODBs). By adding a reference type and four operations to CPL - dereference, method invocation, identity test and class type cast - it is possible to express a large class of interesting "safe" queries against OODBs. As an example of how the extended CPL can be used to query an OODB, we will describe how the extended language has been used as a query interface to Shore databases.