Beyond SQL: Two generic problems

As it was mentioned in Section 1.3 one principal limitation of the RDB is the problem with handling recursive queries, with its specific mathematical formulation of finding transitive closure. For practical information processing the following classes of problems of this kind, which are hard to solve in SQL, are defined below:

C1

Traversal of structurally complex data structures (such as graphs, trees, terms, lists etc.).

C2

Search for Admissible Solutions under specified constraints (finding specific subsets of a given set, generation of structural solutions satisfying specific constraints etc.).

This two classes cover many different problems such as: plan generation, searching for acceptable or optimal solutions, analysis of structures, design of structural object solutions, decision support systems, constraint programming problems. These problems can be tackled by introducing rule-based processing to the database systems.

The ultimate goal of this work is focused on extending database methodology, so that even more complex problems with component solutions specified by these problems can be smoothly approached keeping SQL as outermost communication technology.

The above classes of problems are illustrated with formulation of generic problems presented below.