Requirements traceability information is often represented using traceability matrices, which relate requirements to stakeholders, each other or design modules. In a requirements traceability matrix, each requirement is entered in a row and in a column in the matrix. Where dependencies between different requirements exist, these are recorded in the cell at the row/column intersection.A traceability matrix is an 'at-a-glance' way of seeing the dependencies between requirements.
This is illustrated in the following table that shows a simple traceability matrix that records the dependencies between requirements. A ‘D’ in the row/column intersection illustrates that the requirement in the row depends on the requirement named in the column; an ‘R’ means that there is some other weaker relationship between the requirements. For example, they may both define the requirements for parts of the same subsystem.
Req id. |
1.1 |
1.2 |
1.3 |
2.1 |
2.2 |
2.3 |
3.1 |
3.2 |
|---|---|---|---|---|---|---|---|---|
1.1 |
|
D |
R |
|
|
|
|
|
1.2 |
|
|
D |
|
|
D |
|
D |
1.3 |
R |
|
|
R |
|
|
|
|
2.1 |
|
|
R |
|
D |
|
|
D |
2.2 |
|
|
|
|
|
|
|
D |
2.3 |
|
R |
|
D |
|
|
|
|
3.1 |
|
|
|
|
|
|
|
R |
3.2 |
|
|
|
|
|
|
R |
|
You can use a spreadsheet such as Excel to create and maintain traceability matrices when a small number of requirements have to be managed. However, this becomes unwieldy and expensive to maintain for large systems with many requirements.
For these systems, you should capture traceability information in a requirements database where each requirement is explicitly linked to related requirements. The impact of changes can then be assessed by using the database browsing facilities. Traceability matrices can then be generated automatically.