Theoretical foundations of relational databases and relational database management systems

Theoretical basis

We begin the study of relational databases and relational database management systems. This approach is the most common at the present time, although along with the generally acknowledged advantages it has several disadvantages. The advantages of the relational approach include:

• the presence of a small set of abstractions that make it relatively easy to model most of the common subject areas and allow precise formal definitions, while remaining intuitive;
• the presence of a simple and at the same time powerful mathematical apparatus, relying mainly on set theory and mathematical logic and providing the theoretical basis for a relational approach to the organization of databases;
• the possibility of non-naming manipulation of data without the need to know the specific physical organization of databases in external memory.

Relational systems are not immediately widespread. While the main theoretical results in this area were obtained in the 1970s, and then the first prototypes of relational DBMS appeared, it was considered impossible for a long time to achieve the effective implementation of such systems. However, the advantages noted above and the gradual accumulation of methods and algorithms for the organization of relational databases and their management have led to the fact that already in the mid-80s, relational systems practically supplanted early DBMS from the world market.

At present, the main subject of criticism of relational DBMS is not their lack of efficiency, but some inherent limitations of these systems (a direct consequence of simplicity) when used in so-called non-traditional areas (the most common examples are design automation systems), which require extremely complex data structures. Another often noted disadvantage of relational databases is the impossibility of adequately reflecting the semantics of the subject area. In other words, the possibilities of presenting knowledge about the semantic specificity of the subject area in relational systems are very limited. Modern research in the field of post-relational systems is mainly devoted to the elimination of these shortcomings.