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ARCH.082 Trade off system requirements and constraints

SM-2823 - Populate Confluence page for activity definition: ARCH.082 Trade off system requirements and constraints Finished

GoalDecide on the optimal scope for the system
Requirements met by this process stepISO 15288 6.4.3.3 c) 1
Inputs

AMOD-116 System implementation constraints

AMOD-049 Non-functional requirements implementation

AMOD-050 Stakeholder non-functional requirements

AMOD-045 System capabilities

AMOD-103 Consolidated system functions

AMOD-120 Record of system capabilities and missions

AMOD-121 Record of system and actor functions

AMOD-122 Record of system actors

OutputsAMOD-146 System needs and constraints tradeoff decision record
Methodology

There exists a large number of viable and popular methods for carrying out architectural tradeoffs.

To refine the definition of the goal of this activity: the intent is to determine the set of requirements that can be committed to while achieving the greatest possible value to stakeholders.

For minor decisions, it will be sufficient for the lead system architect to make the decision, and justify it with a Rationale element in the model.

For more complex decisions, a more formal method is needed to provide a robust basis for the decision.

The preferred methodology for complex tradeoffs is Decision Analysis and Resolution, as defined by the Capability Maturity Model Integration programme.

Briefly summarised, the DAR methodology requires:

  • Statement of the problem (i.e. the decision being made)
  • Definition of the alternatives between which the decision is being made
  • Definition of the evaluation criteria
  • Collection of evaluation data
  • Evaluation of data, including weighting of data
  • Selection of preferred solution
  • Agreement of preferred solution with stakeholders (this step to be carred out separately in ARCH.083 Agree the system requirements with stakeholders

A template for AMOD-146 System needs and constraints tradeoff decision record is provided here for applying the DAR methodology: Template for tradeoff records (DAR technique)

Other, comparable architectural tradeoff methods such as ATAM, CESAM's tradeoff method, House of Quality/QFD may be used as long as they define the information above in a clear way.

NB: it is permissible for a solution to be selected that is not shown by the analysis to be the optimal one, if there is an overbearing influence that was not considered in the evaluation criteria. However, in this case, this should be recorded on the template so that the history of the decision is traceable.

Tools and non-human resources

Tradeoff templates/tools as selected by the decision-maker

Team for Capella

CardinalityOnce per tradeoff needed between system needs and external constraints
Completion criteriaThe preferred solution has been selected and its selection justified.
Design reviewARCH.R.4 System review - consolidated
Step done by (Responsible)Lead system architect
Provides input to/assists (Contributes)
  • System architect
  • Engineer
  • Operational concepts architect
Uses outputs (Informed)Stakeholder