ashfordeOU SysML Modeling (systems-engineering-safety/mbse/sysml-modeling)
Use when the task is SysML diagram modeling for model-based systems engineering: choosing diagram kinds, building block definition and internal block diagrams, requirements traceability, parametric constraint analysis, and model viewpoint coverage.
Domain quick reference
- SysML diagram kinds: block definition (bdd), internal block (ibd), parametric (param), requirement (req), activity (act), sequence (seq), state machine (stm), use case (uc), and package (pkg) for model organization.
- Block definition diagram (bdd): declares block hierarchy, part types, value properties, and the system composition tree. Every element referenced by the model needs a definition among its parts.
- Internal block diagram (ibd): shows one block's internal structure: its parts, ports, and the connections (item flows) between them.
- Requirements diagram (req): captures requirements and their relationships (derive, satisfy, verify, refine, trace); traceability links each requirement through design to verification, and safety-critical items need full closure.
- Parametric diagram (param): binds constraint equations to block value properties so that analysis (mass, power, performance) runs on the model instead of in spreadsheets.
- Behavioral kinds: activity (functional flow), sequence (message ordering over time), state machine (modes and state transitions).
- Use case diagram (uc): actors, use cases, and the system boundary at the scoping stage.
- Viewpoints: structure, behavior, requirements, and parametric must all be covered for the model to be complete; a viewpoint that is absent is a gap, not a style choice.
- Model governance: models are configuration-managed artifacts of the development process (ARP4754A context); diagram content and traceability are reviewed like any other engineering data.
Workflow
- Identify the modeling purpose; select the diagram kind that matches it (structure, behavior, requirements, or analysis).
- Draft the block definition diagram: enumerate the blocks, their parts, and the composition hierarchy.
- Detail the internal block diagram for each composite block: parts, ports, and connections.
- Capture requirements in a requirements diagram and link each requirement to the design elements that satisfy it; check traceability closure.
- Add parametric diagrams for constraint-based analysis and bind the constraint equations to block value properties.
- Add behavioral diagrams (activity, sequence, state machine) for functions, interactions, and modes as the model demands.
- Check viewpoint coverage: structure, behavior, requirements, parametric all present; fix gaps.
- Keep the model under configuration management and link it to the verification artifacts.
Pitfalls
- Using a bdd when the question is about internal connections; that is an ibd concern.
- Referencing an element in a bdd that has no block definition; the model is invalid even if the diagram renders.
- Declaring traceability closed while a requirement has no satisfying design element.
- Skipping parametric diagrams and running analysis outside the model; the constraint links are lost.
- Treating an absent viewpoint as optional; a missing viewpoint is a model gap.
- Selecting the diagram by habit instead of by the modeling purpose.
Behavior contract (gate 3)
The diagram-selection, block definition, traceability-closure, and viewpoint logic is exercised by the gate 3 contract test: scripts/test_sysml_modeling.py against scripts/sysml_modeling_logic.py (stdlib unittest, offline). Run: python3 scripts/test_sysml_modeling.py
Compliance
- Standards referenced, not reproduced: ARP4754A text is proprietary (SAE); summary-only per standards-map.yaml and brief 06. SysML diagram semantics are common engineering knowledge.
- compliance: STANDARDS-REF, gated: false.