Notes > Database Systems > Database Design / Application Lifecycle
Before a database design is set into motion, planning is an essential stage. This is typically the responsibility of management within the organisation. Good planning will enable the design and implementation to be successfully completed with the desired results. A general definition of the desired system should also be drawn up at this stage. This would include information such as what the database application should be able to do, to what areas it will be applied, and who will be using it.
Three main factors that should be analysed in the planning are
- What work will need to be done
- The resources needed to complete the work
- How much it will all cost
Requirements Analysis and Collection
Information can be gathered using various techniques. Some of these are listed below:
- Interviewing individuals
- Examining documents
- Using questionnaires
- Using expert knowledge and experience from other design work
Interviewing many individuals can be time consuming but can result in quality feedback which can be used in the system design. Using questionnaires is a quicker and easier way to gain feedback from relevant people. It is hard to ensure that the answers people give are accurate though. Looking at the current documents and paperwork in circulation can be useful in determining what input/output screens should look like for example.
The database design stage will result in a database model that will hopefully support the organisation's goals. The two design approaches that can be used are Bottom Up or Top Down. The Top Down approach starts with a very general overview of the system and details are added in an iterative manner. Bottom Up design involves getting all the details firs then constructing the overall design from the smaller more detailed parts.
The aim of a database design should be to represent all relevant data and the relationships that exist between data items. The database model should also allow for all necessary transactions on the data to be possible.
The following stages follow the database design stage:
- DBMS Selection
- Application Design
- Data Conversion and Loading (if data from an existing system needs to be put into the new database)
- Operational Maintenance (follows the installation of the system)
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