Limitations

The following principal limitations of the Relational Database Management Systems are addressed by this thesis:

• lack of more sophisticated, i.e. rule-based data processing,
• traversal of structurally complex data structures (such as graphs, trees, terms, lists etc.),
• search for Admissible Solutions under specified constraints (finding specific subsets of a given set, generation of structural solutions satisfying specific constraints etc.).

The presented above limitations follow from one generic drawback of relational databases which is the difficulty handling recursive queries [3]. Such a difficulty is one of the eight principal weaknesses of Relational Database Management Systems discussed in [3]^1.1. The most important generic problem following this difficulty is the one mathematically defined as finding transitive closure of relation. Apart from some small-scale examples this operation is computationally infeasible due to its complexity. However certain specific cases (see Section 2.2) can be solved even for practically useful systems.