Functional Architecture
Functional architecture results from:
- Requirements Analysis identifying the functional requirements,
- Decomposing functional requirements into sub-functions,
- Decomposing the associated performance requirements of functional requirements into sub-functions.
This process of decomposition is done to create sub-functions from functional requirements to the point that functional requirements are indivisible from system elements in the design, as shown in fig. 1 below. Synthesized models are compared to the actual designs and specifications in the Design Lifecycle to ensure compliance or to trigger re-evaluation.
Fig. 2 below shows that to enable more complete assessments of viable solutions, it is sometimes required to drive toward near–optimal by considering all the system requirements. This is done by exhibiting alternative functional views, including those that demonstrate functional linkages with current assets.
Physical Architecture
Physical Architecture is created by one logical model or a combination of several logical models of the physical solution. Logical models consist of block diagrams, schematics, and conceptual design drawings, as shown in fig. 3 below. These three components describe the system form, arrangement of system components, and associated interfaces.
As shown in fig.4, physical architecture development can be described as an iterative and recursive procedure to serve the system requirements along with the dynamic needs of functional architecture. Given that the process of creating physical architecture ends after the system has been completely decomposed or broken down to the smallest system element or configuration item, it is prudent to identify design drivers as the first step.
Comparison
There are two main differences between functional and physical architecture. First, while functional architecture concerns are limited to identifying functional elements of a system, physical architecture goes beyond identifying functional elements by identifying the devices and specific subsystems involved.
Second, in case of an obstacle in design implementation, the physical design offers better troubleshooting, while the functional architecture can only be considered for review.