A system must have a purpose, be functional, respond to an identified need, and achieve its overall objective in a cost-effective manner-- a system must respond to an identified functional need.
To respond to a functional need, a system must include elements that relate directly to the accomplishment of a given scenario or mission profile, and elements of logistics and maintenance and support infrastructure that must be available and in place in the event of failure of the prime elements
The system operational requirements document provides the foundation for all subsequent designs and development, test and evaluation, production/construction, and system maintenance and support activities.
Technical Performance Measures (TPMs) are those quantitative measures (metrics) which an interconnected system must deliver in order for the system to accomplish its mission. TPMs must be both specific and prioritized as part of the initial system requirements definition process. The TPMs define the criteria for the design, and the prioritization provides foundation for trade-offs and resulting compromise in design when necessary.
Most engineers are taught to approach their design problems using critical analysis and optimization based on sound engineering practices based on the scientific method and proven principles. Experience teaches (lessons learned) that "non-engineering" factors must be definitely involved in the design and architecting processes. |
The heuristics design methodology is based on "common sense" and common sense comes from the collective experience and is stated in a simple and concise manner.
These simple and concise statements of experience are called heuristics. They exist in the hundreds in architecting and engineering; they are the most practical and pragmatic tools in the architects kit of tools.
The art lies not in the wisdom of the heuristics, but in the wisdom of knowing which heuristics apply (in advance) to the current project.
Systems architecting provides a focus on delivering the desired customer satisfaction (purpose driven systems).
However, not all systems start from the customer driven "need." Some systems start from the builder's perception of marketplace need or opportunity. These are called builder-architected systems. There are important differences in the architectural approach and the associated heuristics
The architect's responsibility retains all the activities of the classical purpose-driven systems, but includes additional architect responsibilities for technology-driven systems. These added responsibilities are needed to identify and manage the extra risks and uncertainties inherent in technology-drive systems and products.
