Introduction

Traceability needs to be implemented throughout any development. This must include vertical traceability, between levels of abstraction (for example, from a Product Requirement to one or more User Needs) and horizontal traceability (for example from a Test Case to a Product Requirement).

Uses of Traceability

Traceability information is fundamental to impact analysis, particularly in assessing the impact of a proposed change. It is also fundamental to coverage analysis, both in the sense of ensuring that all relevant items at one level of specification or development are adequately reflected at the next level, and also to assist in assessing test coverage. For completeness, each requirement stated at one level of abstraction, must satisfy one or more requirements at the next higher level. Similarly, each requirement must be verified or validated by at least one verification or validation action.

Traceability Relationships

The following diagram shows the basic traceability relationships recommended between requirements items.

The relationships are labeled with their names. The names reflect the nature of the relationship, and are named to represent an individual relationship, not the set. Note that these are logical relationships, and may not have any physical representation (though they usually will). In some cases it is possible to reduce the amount of traceability information to manage by tracing only "higher-level" requirements. However, the cost of doing this is that the granularity of trace information does not permit detailed analysis and can become almost meaningless if taken over more than one level of requirement (for example, sub-system requirement -> product requirement -> user need).

Test Traceability

It is also necessary to be able to trace between test information and requirements. The following diagram shows how this is implemented in the current process.

As with the previous diagram, information unrelated to the current traceability is omitted.

Other Traceability

Other forms of traceability will be needed, these include:

• Design – Requirements
• Validation and Verification
• Risks – Requirements