Abstract
Path expressions, a central ingredient of query languages for object-oriented databases, are currently used as a purely navigational vehicle. We argue that this does not fully exploit their potential expressive power as a tool to specify connections between objects. In particular, a user should not be required to specify a path to be followed in full, but rather should provide enough information so that the system can infer missing details automatically. We present and study an extended mechanism for path expressions which resembles the omission of joins in universal relation interfaces. The semantics of our mechanism is given in the general framework of a calculus-like query language. Techniques from semantic query optimization are employed to obtain efficient specifications. We also consider the possibility that links can be traversed backwards, which subsumes previous proposals to specify inverse relationships at the schema level and also fully exploits the meaning of inheritance links.
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