Compare and contrast the three phases of database design
Database design is a combination of stages that are interdependent to each other to facilitate its design, development, implementation of database systems. For good database designs, some phases are followed to achieve the goal of an ideal database. Besides, it helps to have a database that is easy to maintain, cost-effective and facilitate an organized, practical design. Connolly and his friend Begg introduced three development phases which begin with conceptual to logical and end with the physical stage. These phases differ from each other but are interdependent in the designing process.
The first phase, known as conceptualization involves designing a database without any hardware and software resources being needed. This stage, the designer focus is to come up with a model which will be vital for the next step. The model is the first thing to be developed, and it is referred to be the abstract design. The main target of this stage involves describing the data to be stored in the database; the relationship of data stored. Moreover, the constraints on the data are also defined in this phase. They are hence coming up with a representative structure of the database. If changes in the selection of the database management software and hardware, this phase is not affected at all.
The other stage is the logical design which involves taking the designed model in the first stage, and the application of database management system knowledge is used in this stage. The data is, therefore, normalized and testing for its accuracy is conducted. In this phase, there are no physical entities denoted. The output of this stage is model, including an entity-relationship diagram, the relational representation and the documentation. Moreover, the main goal is defining the models for a particular database management system. In this phase, the database engineer uses a whiteboard or a paper to visualize the idea of the logical model.
The last phase, namely the physical design, takes the logical phase output and adds the database management system consigned for the enterprise. Besides, it enables the ability to define physical entities hence the physical layout of the database is described here. The activity involves creating tables, defining relationships and constrains, keys as well as setting up security measures. The phase also involves file organization and the full database structure. The indexing techniques vary from one database vendor to another. The stage is also interdependent to the operating system that carries out the management activities.
Indeed, we can conclude that these phases are dependent on each other hence showing that a successful process would start from the concept to physical design of the database., and later implementation. The three phases act as a guideline for the designer to use to ensure normalization and all the small details are not left out in the process. The steps aim for meeting the user need, hardware platform, the database programming language and performance issues are also considered when developing a database using this methodology of three phases. It should be noted that the design stages define the level of abstraction of the database.