Requirements traceability

Requirements traceability is a sub-discipline of requirements management within software development and systems engineering. Traceability as a general term is defined by the IEEE Systems and Software Engineering Vocabulary as (1) the degree to which a relationship can be established between two or more products of the development process, especially products having a predecessor-successor or master-subordinate relationship to one another; (2) the identification and documentation of derivation paths (upward) and allocation or flowdown paths (downward) of work products in the work product hierarchy; (3) the degree to which each element in a software development product establishes its reason for existing; and (4) discernible association among two or more logical entities, such as requirements, system elements, verifications, or tasks. Requirements traceability is a sub-discipline of requirements management within software development and systems engineering. Traceability as a general term is defined by the IEEE Systems and Software Engineering Vocabulary as (1) the degree to which a relationship can be established between two or more products of the development process, especially products having a predecessor-successor or master-subordinate relationship to one another; (2) the identification and documentation of derivation paths (upward) and allocation or flowdown paths (downward) of work products in the work product hierarchy; (3) the degree to which each element in a software development product establishes its reason for existing; and (4) discernible association among two or more logical entities, such as requirements, system elements, verifications, or tasks. Requirements traceability in particular, is defined as 'the ability to describe and follow the life of a requirement in both a forwards and backwards direction (i.e., from its origins, through its development and specification, to its subsequent deployment and use, and through periods of ongoing refinement and iteration in any of these phases)'. In the requirements engineering field, traceability is about understanding how high-level requirements – objectives, goals, aims, aspirations, expectations, needs – are transformed into low-level requirements. It is therefore primarily concerned with satisfaction relationships between layers of information (aka artifacts). However, traceability may document relationships between many kinds of development artifacts, such as requirements, specification statements, designs, tests, models and developed components. For example, it is common practice to capture verification relationships to demonstrate that a requirement is verified by a certain test artifact. Traceability is especially relevant when developing safety-critical systems and therefore prescribed by safety guidelines, such as DO178C, ISO 26262, and IEC61508. A common requirement of these guidelines is that critical requirements must be verified and that this verification must be demonstrated through traceability. Pre-Requirements Traceability. Requirements come from different sources, like the business person ordering the product, the marketing manager and the actual user. These people all have different requirements of the product. Using requirements traceability, an implemented feature can be traced back to the person or group that wanted it during the requirements elicitation. This can be used during the development process to prioritize the requirement, determining how valuable the requirement is to a specific user. It can also be used after the deployment to see why certain unused features found during user studies were required in the first place. Post-Requirements Traceability. Not only the requirements themselves should be traced but also the requirements relationship with all the artifacts associated with it, such as models, analysis results, test cases, test procedures, test results and documentation of all kinds. Even people and user groups associated with requirements should be traceable. Requirements are realized into design artifacts, implementation, and finally, verified. Artifacts tied to the latter stages should be traced back to the requirements as well. This is typically done via a requirements traceability matrix. Establishing traceability beyond requirements into design, implementation, and verification artifacts can become difficult. When implementing software requirements for instance, the requirements may be in a requirements management tool, while the design artifacts may be in a tool such as MagicDraw, Mathworks Simulink, Rational Rhapsody, and Microsoft Visio.Furthermore, implementation artifacts will likely be in the form of source files, links to which can be established in various ways at various scopes. Verification artifacts such as those generated by internal tests or formal verification tools (e.g., LDRA Testbed suite, Parasoft DTP, and SCADE)