Methods for Verifying Functional Architecture

6.5.4 Verify the Functional Architecture

The functional architecture is the FFBDs and the allocated requirements. The collection of all documentation developed during the functional analysis and allocation task is called the functional view. The final task in defining the functional architecture is to review all of the functional view documentation for consistency and accuracy. Check the functions defined for each mode and sub mode to verify that no functions are missing and that the requirements allocated to each function are appropriate for each mode and sub mode. An example of a matrix of modes to functions useful for verifying that all top level functions needed for each sub mode of a toaster in its In Use Mode are defined properly is shown in Figure 6- 29. This example only examines one system mode but the process for examining all modes and all lower level functions is just an extension of the matrix.

The methodology of verifying functional design by using two different tools to describe the same functional requirements also applies to mode transitions. Figure 6-30 is an example of a matrix used to define the allowed transitions among modes of the In Use mode as previously defined with a mode transition diagram in Figure 6-11. Although this is a trivial example it illustrates the methodology.

Figures 6-29 An example of a Functions to System Modes matrix that facilitates verifying that all functions are defined for all modes.

Figure 6-30 Allowable mode transitions can be defined in a matrix as well as in a diagram.

Revisit the documentation in the operational view to verify that the functional architecture accounts for every function necessary to fulfill the operational requirements and that no unnecessary functions have been added. Verify that every top level performance and constraining requirement is flowed down, allocated and traceable to lower level requirements and that there are no lower level requirements that are not traceable to a top level requirement.