The activities described below should be considered in the context of the Overview of the Systems Approach topic at the start of this KA. The final topic in this KA, Applying the Systems Approach, considers the dynamic aspects of how these activities are used as part of the systems approach and how this relates in detail to elements of systems engineering (SE).
System Analysis
System analysis is an activity in the systems approach that evaluates one or more system artifacts created during the activities involved in Synthesizing Possible Solutions, such as:
• Defining assessment criteria based on the required properties and behavior of an identified problem or opportunity system situation.
• Accessing the properties and behavior of each candidate solution in comparison to the criteria.
• Comparing the assessments of the candidate solutions and identification of any that could resolve the problem or exploit the opportunities, along with the selection of candidates that should be further explored.
The problem context for an engineered system will include a logical or ideal system solution description. It is assumed that the solution that “best” matches the ideal one will be the most acceptable solution to the stakeholders. Note, as discussed below, the “best” solution should include an understanding of cost and risk, as well as effectiveness. The problem context may include a soft system conceptual model describing the logical elements of a system to resolve the problem situation and how these are perceived by different stakeholders (Checkland 1999). This soft context view will provide additional criteria for the analysis process, which may become the critical issue in selecting between two equally effective solution alternatives. Hence, analysis is often not a one-time process of solution selection; rather, it is used in combination with problem understanding and solution synthesis to progress towards a more complete understanding of problems and solutions over time.
Effectiveness Analysis
Effectiveness studies use the problem or opportunity system context as a starting point. The effectiveness of a synthesized system solution will include performance criteria associated with both the system’s primary and enabling functions. These are derived from the system’s purpose, in order to enable the realization of stakeholder needs in one or more, wider system contexts. For a service system or enterprise system the criteria will be more directly linked to the identified user needs or enterprise goals. Typical qualities for such systems include agility, resilience, flexibility, In addition to assessments of the absolute effectiveness of a given solution system, systems engineers must also be able to combine effectiveness with the limitations of cost and timescales included in the problem context. In general, the role of system analysis is to identify the proposed solutions which can provide some effectiveness within the cost and time allocated to any given iteration of the systems approach. If none of the solutions can deliver an effectiveness level that justifies the proposed investment, then it is necessary to return to the original framing of the problem. If at least one solution is assessed as sufficiently effective, then a choice between solutions can be proposed.
Systems Principles of System Analysis
From the discussions above, the following general principles of systems analysis can be defined:
1.- Systems analysis is an iterative activity consisting of trade studies made between various solution options from the systems synthesis activity.
2.- Systems analysis uses assessment criteria based upon a problem or opportunity system description.
3.- These criteria will be based around an ideal system description that assumes a hard system problem context can be defined.
4.- The criteria must consider required system behavior and properties of the complete solution in all of the possible wider system contexts and environments.
5.- Trade studies requires equal consideration to the primary system and the enabling system working as a single sytem to address the User need. These trades need to consider system requirements for Key Performance Parameters (KPPs), systems safety, security, and affordability across the entire life cycle
6.- This idea system description may be supported by soft system descriptions from which additional “soft” criteria may be defined (e.g., a stakeholder preference for or against certain kinds of solutions and relevant social, political, or cultural conventions to be considered in the likely solution environment, etc.).
7.- At a minimum, the assessment criteria should include the constraints on cost and time scales acceptable to stakeholders.
9.- A trade study should consider a “system of assessment criteria”, designating special attention to the limitations and dependencies between individual criteria.
10.- Trade studies need to deal with both objective and subjective criteria. Care must be taken to assess the sensitivity of the overall assessment to particular criteria.