Exact Requirements
What
Exact requirements
- Characteristics a customer needs to solve a problem or to reach a goal.
- Characteristics of system-to-be to satisfy a contract.
How
The dish
Exact Requirements
Ingredients
Process
In order to specify the exact requirements you need to locate, analyse and describe the needs of the customer in an iterative process.
To locate the needs, you have to listen carefully to the customer's storytelling. A good tool is to draw a Rich Picture to get an understanding of the functionality. Then you analyse the information to get a structured picture of the problem. This analysis may include Preliminary Use Cases, System Definition and even Prototyping. Then you make a description and present it to the customer in order to secure that you have understood his needs correctly. You may have to go through this process several times before you are able to locate all the exact requirements. It is important that the requirements are:
1. unambiguous
2. complete
3. consistent
4. correct
5. testable
6. changeable
7. traceable
in order to make the verification and product accept easy and without conflicts.
Why
We have to realise that it is a complicated and iterative process to identify the customer's needs. Especially the software can be highly abstract reasoning which might be difficult to understand for the customer. A process has input data, activity and output data. The pattern to locate the exact requirements is therefore:
- Input data: The customer's description of his vision, his needs and the concept for the project.
- Activity:
Run through these activities repeatedly: Capture Requirements -> Analyse Requirements -> Specify Requirements -> Verify Requirements
- Output data: The result from the process will be a description of the exact requirements.
Example
Input data is the Rich Picture and the customer's description of his house heating and solar energy system.
Activity:
To capture the requirements from the input data. The system contains four main components:
1 The central heating with the boiler, motor-controlled mixer, pump, supply temperature sensor and radiators.
2 The hot water tank with the boiler, pump, the boiler-driven heating coil, the mains-driven heating coil and the relay to switch between the two coils.
3 The solar energy system
4 And additionally; the control system that the developer has to make according to the customer's description!
To analyse the requirements, the developer has to work through the customer's information and make a system description in his own words. This ensures that he has understood all of the customer's needs and he gets an idea of how to solve the problem and how to verify his solution.
To specify the requirements, the developer uses his solution and verification model.
