4.1.1 Modeling Databases
A model is a representation or a simplified copy of something more complex. You use models to examine large or complicated structures which are difficult to work with directly. For example, models of air plane wings are tested and scale models of buildings are created. A data model is a tool which allows the developer to construct a picture of the data within an organization or a part of an organization. It is not a picture of what the computer sees, but of what the user and business sees.
Logical Data Models are high level or conceptual models which describe data in terms of the user perspective and business rules. A logical data model represents the business. A logical data model looks at the basic pieces of information and the inter-dependencies between the information. Logical data models are defined in terms of entities, attributes, and relationships. They reflect the business, its information and rules. It is not designed to represent the Architect's perception of the physical database to be implemented.
LANSA provides a modeling tool that allow the systems analyst to build up and manipulate a complete logical data model comprising elements, entities and relationships and applies data analysis rules to ensure that the model is properly normalized. This tool allows the physical database to be generated from the logical model, but recognizes the fact that there will be differences between the two. For example, for performance reasons, you may not wish to implement a fully normalized database.
A modeling tool documents the logical data model in such a way that it is understood by users. It can be reviewed and verified by the users as part of the analysis/design process before any physical database is built.
A modeling tool improves the developers productivity by automating the build of the physical database. The modeler helps the developer to create quality databases with a consistent standard. It supports the concept of a corporate data types and allows the developer to define standards for the implemented physical database.
If you are building a new application or re-engineering an application, it is highly recommended that you use a modeling tool to build your application database. (Refer to Using a Modeling Tool.)