Simplifying the Formulation of a Wide Range of Object-Oriented Complex Queries

We present a model that simplifies the formulation of a wide range of complex, mainly selection-based, objectoriented queries, including linear recursive queries. They are complex because it is almost impossible for naive users to predict the formulation of their predicate expressions. Naive users are mainly decision makers who are most probably not computer professionals. Therefore, it is necessary to provide them with a straightforward and easyto-handle approach to retrieve the information required for the decision making process. To achieve this, the definition of the selection operation and the predicate definition are adjusted to make it possible to have in the output only a subset of the objects from the actual result of a linear recursive query. Otherwise, it is infeasible to achieve the same output without an additional selection with a complicated predicate. We also define an operation that facilitates applying aggregate functions on objects. The two operations proved to be very useful and necessary to study the characteristics of trees and directed graphs. The presented model has been implemented as a part of our object-oriented database management system prototype.