Procedures in Object-Oriented Query Languages
Kazimierz Subieta, Yahiko Kambayashi, Jacek Leszczyłowski · 1995
We follow the stack-baaed approach to query languages which is a new formal and intel-lectual paradigm for integrating querying and programming for object-oriented databases. Queries are considered generalized program-ing expressions which may be used within macroscopic imperative statements, such as creating, updating, inserting, and deleting data objects. Queries may be also used as pro-cedures ’ parameters, as well as determine the output from functional procedures (SQL-like views). The semantics, including generalized query operators (selection, projection, naviga-tion, join, quantifiers, etc.), is defined in terms of operations on two stacks. The environment stack deals with the scope control and bind-ing names. The result stack stores intermedi-ate and final query results. We discuss defini-tions of object-oriented concepts and present variants of parameter passing methods. Fi-nally, we indicate a potential of the approach for query optimization based on rewriting. 1