Conceptual Design versus Logical Design

Conceptual Data Design Prepared at beginning of project High level view of how the client sees the data Top down process Not concerned with details Normally prepared using brainstorming approach Identification of Entities, Attributes and Relationships represented using Entity Relationship Diagram ERD is constantly modified as project progresses and more is learnt about application’s data

Logical Data Design Detailed representation of application’s data Bottom-up process Purpose of logical data design is to represent application data in the form of related 2- dimensional relations which will correspond to the tables created in a relational database Details obtained by analysing representative samples of application’s user views or prototyping user views

User View A user view is a view of the data presented by the application to the user, i.e. a set of requirements that are necessary to support the operations of a particular user User views may include: input screen, output screen, input form, detailed report, summary report User view should present sample data User view may be either a prototype or an actual sample Should collect a representative sample of user views from different areas in the application Technique of normalization is applied to each user view to identify relations (i.e. tables)