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Reduce code devt cost using traceability tools

Posted: 22 Dec 2011     Print Version  Bookmark and Share

Keywords:requirements-driven development  product lifecycle  impact analysis 

When an organisation delivers a product based in software, that software and its requirements, design, and verification artifacts are usually delivered with an RTM. Often, teams put off assembling the artifacts and the RTM until the last minute, scrambling to assemble them just prior to delivery. Inconsistencies that may be latent defects are then likely to be found during final traceability exercises. At this point, those inconsistencies are expensive to correct and may result in unexpected delays and cost overruns.

If teams maintain the RTM throughout the entire development cycle, however, the delivery process becomes far less painful. Traceability issues can be worked out as they arise throughout the lifecycle, and artifacts are typically thoroughly vetted long before delivery.

Advantages of traceability
To fully appreciate the benefits of good traceability practices, it is necessary to understand the complexities introduced by the latter phases of development. As requirements are validated and the project enters the detailed design phase, the number of artifacts proliferates rapidly. Implementation and verification phases add code and test data to the RTM. As the number of engineers reaches full staffing complement and the full complexity of the product comes into view, risks and inefficiencies in the project rapidly translate to growing costs. Schedule slips further with each defect identified. Budgetary changes, scope changes, and even healthy innovation further compound the flux in the system. Meanwhile, preserving the integrity of the RTM requires maintaining traceability from design artifacts to code, test cases of various forms, and the resulting test data.

As insurmountable as this number of variables may seem, traceability tools can tame the process. Maintaining discipline in traceability throughout the system with traceability tools greatly reduces the defects that can disrupt the development process. In the scenarios below, traceability-related analysis is used to reconcile issues with upstream requirements, assess costs for newly added features, and better monitor project progress.

In the first scenario, an engineer implementing behaviour described within a software requirements specification (SRS) may find inconsistencies or errors in the requirements definition. If traceability has been maintained, the engineer can run upstream analysis to find how the error impacts system-level requirements (figure 1). He or she can then communicate with the various owners of these requirements and design artifacts to better describe the issue for a successful resolution.

Figure 1: Here you can see the upstream impact of requirement SRS_0001. The requirements highlighted in the Prime Item Development Specification (PIDS) and the Interface Control Document (ICD) are system-level requirements upstream in the specification tree to the Software Requirements Specification (SRS).

Without this upstream traceability available, an engineer may find a technical solution that requires some requirement or design modifications but may be unable or unsuccessful in communicating these changes upstream. The potential of such limitations can easily result in defects embedded in the system that will likely not be noticed until verification.

Figure 2: Notice how the Requirement column (left) shows system-level requirements (PROJ_SYS_0012). The Downstream column (centre) shows that software requirements PROJ_SRS_0022 and PROJ_SRS_0032 are decomposed from PROJ_SYS_0012. The Mapped Files column (right) offers associated source files and prototypes as they are mapped to the software requirements. Hence a modification of PROJ_SYS_0012 impacts the files and prototypes listed.

When scope creep enters a project and its RTM, it is necessary to very quickly assess the impact of that creep with respect to cost, staffing, and other logistics. Requirements changes can affect scope change in the form of newly added, modified, and deleted requirements (figure 2). A well-maintained RTM and some downstream impact analysis quickly measures the impact to the software.

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