Thursday, September 18, 2008

Traceability Matrix

A traceability matrix is a table that correlates any two base lined documents that require a many to many relationship to determine the completeness of the relationship. It is often used with high-level requirements (sometimes known as marketing requirements) and detailed requirements of the software product to the matching parts of high-level design, detailed design, test plan, and test cases.
Common usage is to take the identifier for each of the items of one document and place them in the left column. The identifiers for the other document are placed across the top row. When an item in the left column is related to an item across the top, a mark is placed in the intersecting cell. The numbers of relationships are added up for each row and each column. This value indicates the mapping of the two items. Zero values indicate that no relationship exists. It must be determined if one must be made. Large values imply that the item is too complex and should be simplified.
To ease the creation of traceability matrices, it is advisable to add the relationships to the source documents for both backward traceability and forward traceability. In other words, when an item is changed in one base lined document, it's easy to see what needs to be changed in the other.

A table that traces the requirements to the system deliverable component for that stage that responds to the requirement.
Size and Format
For each requirement, identify the component in the current stage that responds to the requirement. The requirement may be mapped to such items as a hardware component, an application unit, or a section of a design specification.

Requirements of Traceability Matrix
Traceability matrices can be established using a variety of tools including requirements management software, databases, spreadsheets, or even with tables or hyperlinks in a word processor.
A traceability matrix is created by associating requirements with the work products that satisfy them. Tests are associated with the requirements on which they are based and the product tested to meet the requirement.

Above is a simple traceability matrix structure. There can be more things included in a traceability matrix than shown. In traceability, the relationship of driver to satisfier can be one-to-one, one-to-many, many-to-one, or many-to-many.
Traceability requires unique identifiers for each requirement and product. Numbers for products are established in a configuration management (CM) plan.
Traceability ensures completeness, that all lower level requirements come from higher level requirements, and that all higher level requirements are allocated to lower level requirements. Traceability is also used to manage change and provides the basis for test planning.

Baseline Traceability Matrix

A table that documents the requirements of the system for use in subsequent stages to confirm that all requirements have been met.

Size and Format
Document each requirement to be traced. The requirement may be mapped to such things as a hardware component, an application unit, or a section of a design specification.

Building a Traceability Matrix

Use a Traceability Matrix to:
• verify and validate system specifications
• ensure that all final deliverable documents are included in the system specification, such as process models and data models
• improve the quality of a system by identifying requirements that are not addressed by configuration items during design and code reviews and by identifying extra configuration items that are not required. Examples of configuration items are software modules and hardware devices.
• provide input to change requests and future project plans when missing requirements are identified.
• provide a guide for system and acceptance test plans of what needs to be tested.

Useful Traceability Matrices
Various traceability matrices may be utilized throughout the system life cycle. Useful ones include:
• Functional specification to requirements document: It shows that each requirement (obtained from a preliminary requirements statement provided by the customer or produced in the Concept Definition stage) has been covered in an appropriate section of the functional specification.
• Top level configuration item to functional specification: For example, a top level configuration item, Workstation, may be one of the configuration items that satisfies the function Input Order Information. On the matrix, each configuration item would be written down the left hand column and each function would be written across the top.
• Low level configuration item to top level configuration item: For example, the top level configuration item, Workstation, may contain the low level configuration items Monitor, CPU, keyboard, and network interface card.
• Design specification to functional specification verifies that each function has been covered in the design.
• System test plan to functional specification ensures you have identified a test case or test scenario for each process and each requirement in the functional specification.
Although the construction and maintenance of traceability matrices may be time-consuming, they are a quick reference during verification and validation tasks.

Sample Traceability Matrix
A traceability matrix is a report from the requirements database or repository. What information the report contains depends on your need. Information requirements determine the associated information that you store with the requirements. Requirements management tools capture associated information or provide the capability to add it.

The examples show forward and backward tracing between user and system requirements. User requirement identifiers begin with "U" and system requirements with "S." Tracing S12 to its source makes it clear this requirement is erroneous: it must be eliminated, rewritten, or the traceability corrected.

For requirements tracing and resulting reports to work, the requirements must be of good quality. Requirements of poor quality transfer work to subsequent phases of the SDLC, increasing cost and schedule and creating disputes with the customer.

A variety of reports are necessary to manage requirements. Reporting needs should be determined at the start of the effort and documented in the requirements management plan.

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