System Development Methodology
System Development Methodology (SDM) is primarily being used for the development of IT projects. SDM is a waterfall method. This means that a phase only starts when a previous phase has been closed. This counts for all phases, except the first one.
SDM is a top-down model. Starting from the system as a whole, its description becomes more detailed as the design progresses.
History
SDM was developed in 1970 by a company known as PANDATA, now part of Cap Gemini, by order of three Dutch companies: AKZO, Nationale Nederlanden and PTT. It was revised in 1987. This version is commonly known as SDM2.
Differences between SDM and SDM2
 | This article may require copy editing for grammar, style, cohesion, tone, or spelling. (January 2007) |
During the SDM functional, design phase problems were documented. They were necessary for the making of the functional design. This documentation in front was replaced in the new phase design. This phase design is global and detailed design. In the global design the principles of functionality and construction as well as their relations are documented.
The method
As stated before, SDM is a method based on phases. Before every phase, an agreement needs to be reached detailing the activities for that phase. These documents are known as milestone documents. Several uses for these documents exist:
- Traceability — Through applying deadlines to milestone documents, clients can keep track on whether a project is on schedule
- Consolidation — By approving a milestone document, it gains a certain status. The client can not change any of the specifications later during development.
- If necessary, the project can be aborted. This mostly happens during the start of development.
Phases
The method uses 7 phases which successively are being executed. The phases are:
- Problem definition
- Definition study
- Design
- Building system
- Testing
- Implementation
- Operation and Support
Upon completion of a phase, it is decided whether to go on to the next phase or not; the terms 'Go' and 'NO-GO' are used for this. The next phase will not start until a 'Go' is given, while if there is a 'NO-GO', the project either stays in the current phase to be improved or is cancelled completely.
Problem definition
In this phase, the problems that have to be solved by the project are defined. The current and desired situations are analysed, and goals for the project are decided upon. In this phase, it is important to consider the needs of all parties, such as future users and their management. Often, their expectations clash, causing problems later during development or during use of the system.
Definition study
In this phase, a more in-depth study of the project is made. The organization is analysed to determine their needs and determine the impact of the system on the organization. The requirements for the system are discussed and decided upon. The feasibility of the project is determined. Aspects that can be considered to determine feasibility are:
- Advisable — Are the resources (both time and knowledge) available to complete the project.
- Significance — Does the current system need to be replaced?
- Technique — Can the available equipment handle the requirements the system places on it?
- Economics — Are the costs of developing the system lower than the profit made from using it?
- Organization — Will the organization be able to use the new system?
- Legal — Does the new system conflict with existing laws?
Design
In this phase, the design for the product is made. After the definition study has determined what the system needs to do, the design determines how this will be done. This often results in two documents: The functional design, explaining what each part of the system does, and the technical design, explaining how each part of the system is going to work.
SDM2 split this step in two parts.
- Global design — This phase combines a functional and technical design and only gives a broad design for the system. Often, the architecture of the system is described here.
- Detailed design — This phase continues the global design by creating more detailed designs to the point where they can be used to build the system itself. This is split to create separate parts of the system to be created.
Building the system
In this phase, the design is converted to a working system. The actual way this is done will depend on the system used. Where in older systems programmers often had to write all of the code, newer systems allow the programmers to convert the design into code directly, leaving less work to be done and a smaller chance for errors. At the same type, the system becomes more reliant on the design—if the design has been properly tested, the proper code will be generated, but if the design is not fully correct, the code will be incorrect without a programmer to look for such problems.
Testing
The testing consists of two steps: A system test and an acceptance test.
During the system test the development team—or a separate testing team—tests the system. Most of this will be focused on the technical aspects: does the system work as it should, or are there bugs still present? Bugs that are found in this phase will be fixed. At the ending of this phase, the program should work properly.
During the acceptance test, the end-users will test the system. They will test to see if the program does what they want it to do. They will not test every possible scenario, but they will test to see if the program does what they want and expect it to do and that it works in an easy way. Bugs that are found in this phase will be reported to the development team so that they can fix these bugs.
Implementation
During this phase, the final version of the system is implemented by the organization: the hardware is set up, the software is installed, end user documentation is created and, end users trained to use the program, existing data is entered into the system.
Operation and Support
Once the system has been implemented, it is used within the organization. During its lifetime, it needs to be kept running and possibly enhanced.