A query model for object-oriented databases
Reda Alhajj, M. Erol Arkun · 2002
A formal object-oriented query model is described in terms of an object algebra. Both the structure and the behavior of objects are handled. An operand and the output from a query in the object algebra are defined to have a pair of sets, i.e. a set of objects and a set of message expressions, where a message expression is a valid sequence of messages. The closure property is therefore maintained in a natural way. In addition, it is proven that the output from a query has the characteristics of a class; hence, the inheritance relationship between the operand and the output from a query is derived.>