A Methodology of A Database Schema Design Using The Subschemas

The initial assumption is that a database schema is produced by the integration of simultaneously and independently designed subschemas. The notion of a subschema is defined using the concepts of the relational data model, according to the appropriate external schema, which is used to express a user view onto a future database, on the conceptual level. The process of simultaneous design of subschemas usually may lead to the collisions in expressing the real system constraints and business rules. If these collisions exist, some of the subschemas are not consistent in a formal sense with the database schema, which is obtained by the integration of a set of subschemas. The programs made over the inconsistent subschemas do not guarantee safe database updates. The aim of the paper is to present a process of a database schema design using the subschemas, that assure the design of the consistent subschemas and formally correct database schema. A common algorithm for checking of the constraint consistency between the database schema and subschemas, on the level of the same constraint type, is presented too.