A query system for object-relational database

The converging trend of relational database technology and object-oriented database technology results in object-relational database systems, which opens up the type system of the traditional model to allow for the addition of new data types, such as ADTs, references and collections. Traditional relational query languages need to be extended to handle the more complex structure, so does the query system which form the underlying structure of query languages. In this paper, we propose an object-relational data model which extends the relational model with add-on object features. We then define an algebra which are extended from its relational counterpart. It fully incorporates relational query operations, while supporting some new features to handle complex data, such as ADTs and bulk types. The algebra supports access to relationships implied by the database schemas. Compared with existing object-oriented query algebras, it adopts a different approach to handle object identities (OID). The algebra can be used as an input language for the query optimizers.