| implicit requirement | has definition A requirement not stated explicitly in the requirements document |  |
| is a subtopic of 10.1 - Basic Definitions |  |
| is discovered when a user or tester runs the system |  |
| is a kind of requirement |  |
| requirement | can be gathered from various stakeholders, other software systems and any documentation that might be available |  |
| changes regularly |  |
| does not describe how the system will be implemented |  |
| does not describe the domain |  |
| has part problem statement |  |
| indicates how the system is to behave |  |
| is concise |  |
| is expressed as a fact |  |
| is grouped with other requirements into a requirements document |  |
| is normally expressed in a natural language such as English (using present tense and active voice), sometimes supplemented by a formal mathematical language, and often by some form of diagram |  |
| may be given a unique number for traceability |  |
| may be shown as a diagram |  |
| must be agreed upon by all stakeholders |  |
| should be important for the solution of the current problem |  |
| should be logically consistent |  |
| should be realistic with available resources |  |
| should be unambiguous |  |
| should be uniquely identifiable |  |
| should be verifiable |  |
| should be analysed if there is any doubt whether it is realistic |  |
| should be changed whenever the benefits of doing so outweigh the costs |  |
| should be cut if cost-benefit analysis shows that it will have minimum benefit but still cost a lot to develop |  |
| should be expressed using clear and consistent notation, using language that the customers can understand, and consistent with the other requirements |  |
| should have benefits that outweigh the costs of development |  |
| should help solve a customer's problem |  |
| should lead to a system of sufficient quality - one that is sufficiently usable, safe, efficient, reliable and maintainable |  |
| should not indicate how it will be implemented in order to give the designer as much freedom as possible to make decisions |  |
| should not over-constrain the design of the system |  |