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bok:eng:mbse:critique

Model Critique

Definition

Is: What it is

IsNot: What it is not

Rationale

  • Models are not correct by virtue of inspection or by virtue that everybody worked on it.
  • Many different ways to implement same function and inevitably there is a trade-off when a choice is made. A critique of a model provides an outsider's perspective
  • Verify and validate the model for a given project, potentially as part of a non-advocate review
  • Evaluate the current state and achievements on an MBSE effort to determine whether it requires or would benefit from additional funding
  • Evaluate whether a sister project should adopt the MBSE approach based on the current MBSE efforts
  • Evaluate a tool vendor

Performance Qualities

: How to determine the performance of {Thing}

Problem

: What issues are relevant to {Thing}

Precondition

: What conditions are necessary for {Thing} to operate

Postcondition

: What conditions are necessary for {Thing} to produce

Ontology

: What terms/taxonomy are relevant to {Thing}

Methodology

Method

Heuristics

  • Is there a potential for failure due to timing?
  • Has the model used patterns?
  • Does different components react differently to different stimuli
  • Is there consistency
  • Look at interfaces between SOI and context
  • What are the system dynamics and failure
  • What are the rainy day scenarios
  • Do observations on numbers

Proofs

Process

  1. Functionality and Use Cases
    • What are the preconditions for the function
    • Is there any validation vs requirements
    • What happens in case of error/illegal use csae
  2. Structure of the Model
  3. Interfaces
  4. Dependability and Failure Modes
    • Check for any broken/circular relationship/redundant content
    • Touches on security/availability
    • What failure modes are anticipates
    • Has the modeler tested for resilience to failure mode
  5. Concurrency Analysis
    • There are two types concurrency failure (livelock and deadlock)
    • Livelock - When an element constantly changing resulting in a “runaway” state preventing model convergence
    • Deadlock - Two components attempt to share a common resource, blocking access to both
    • It is possible to be under-specified and over-specified
  6. Management and Deployment
    • Has allocated logical to function to structure
    • Who has authority to make changes?
    • Has model lifecycle management process been documented?
  7. Review Against Qualities of Great Models

Parts

Outputs

  • Remarks on whether the model is meeting the intended scope and purpose.
  • Set of observations and data on the model’s strengths and weaknesses. Your findings should relate back to specific instances of the model with data sampling to backup your feedback.
  • An evaluation against each of the qualities of great models, as well as supplementary behaviors or qualities you believe are relevant for an MBSE model.
  • Conclusions and recommendations for the specific rationale for the critique.

Constraints

Thing is refined by

Use Cases

This is specialised by

Generalization Sets: What sets subdivide {Thing}

bok/eng/mbse/critique.txt · Last modified: 2020/07/05 14:09 by anwlur