Most of the information systems nowadays are multi-user systems, that is, they should have a database that many users can use. Application programs depend on the database. A good database design that can accommodate and support all application programs is necessary for an information system to deliver the intended functionality. The system reliability is a measure of the reliability of any of its worst components.
Business analyst ignores the importance of gathering information for the database design. He/she should seek answers to the following questions before database design:
1. What are the subjects/objects of the business? What types of people, places, things, materials, events, etc. are used in this business? How many instances of each object might exist?�Data entities and their descriptions. Business analyst must have thorough knowledge about the data that will be used in application
2. What unique characteristic(s) distinguishes one object from other similar objects? Will this distinguishing feature change over time or is it permanent? Can we miss this characteristic of an object even though we know the object exists?�Primary key
3. What are the characteristics for each object? On what basis are objects referenced, selected, qualified, sorted, and categorized? What information about the object is necessary to run the business?�Attributes and secondary keys
4. How do you use these data? That is, are you the source of the data for the organization, do you refer to the data, do you modify it, or do you destroy it? Who is not permitted to use these data? Who is responsible for establishing legitimate values for this data?�Security controls and understanding who really knows the meaning of data
5. Over what period of time are you interested in these data? Do you need historical trends, current “snapshot” values, and/or estimates or projections? If a characteristic of an object changes over time, must you know the obsolete values?�Cardinality and time dimensions of data
6. Are all instances of each object the same? That is, are there special kinds of each object that are described or handled differently by the organizations? Can some objects be summaries or combinations of more detailed objects?�Supertypes, subtypes, and aggregations
7. Which events imply associations between various objects? What natural activities or transactions of the business involve handling data about several objects of the same or different type?�Relationships, and their cardinality and degree
8. Is each activity or event always handled the same way or are there special circumstances when it is handled differently? Can an event occur with the involvement of only some of the objects, or must all objects be involved? Can the associations between objects change over time (for example, employees change departments)? Are values for data characteristics limited in any way?�Integrity rules, minimum and maximum cardinality, time dimensions of data
A business analyst must have equal interest and rigour in database details, as he/she determines functional and non-functional requirements of an application.