Topic: Understanding SysML through comparison with UML
Due: Nov. 19, 2025
Submission: A single pull request with all your contributions.
Answer briefly
- Purpose and Motivation
Why was SysML created? What limitations of UML does it address?
SysML exists because UML focuses on software. SysML fills the gap for complete systems by supporting hardware, mechanics, electronics, energy flows, and requirements that UML can’t model.
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Modeling Perspective
UML is based on object-oriented concepts, especially the UML Class diagram. How does SysML’s block-based approach differ conceptually from UML’s class-based approach?UML classes are tied to object-oriented software concepts. SysML blocks are neutral — they can represent any system element (hardware, software, physical, logical) without OO constraints.
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Scope
What kinds of system elements can be represented in SysML that are not typically modeled in UML?SysML can model things UML usually can’t: hardware components, physical connections, energy/material flows, requirements, tests, parameters, ports, and full system architecture.
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Focus
Give an example (maybe from your own experiences as a developer/student?) of a system where using UML alone would be insufficient, and explain how SysML can better represent it.Take something like an ESP32-based measurement system (like the one I built in Mechatronics). UML can show the software, but not the sensors, signals, power paths, or requirements. SysML combines all of that — hardware + logic + behavior + requirements — in one consistent model.
- Make a comparison table comparing UML diagrams and SysML diagrams.
- Indicate whether each is reused, modified, or new in SysML.
- For each SysML-specific diagram, write one short sentence about its purpose.
| UML Diagram | SysML Status | SysML Equivalent / New Diagram | Purpose (1 sentence) |
|---|---|---|---|
| Class Diagram | Modified | Block Definition Diagram (BDD) | Defines system elements (blocks), their structure, and relationships. |
| Composite Structure | Modified | Internal Block Diagram (IBD) | Shows internal parts of a block and how they interact via ports/flows. |
| Package Diagram | Reused | Package Diagram | Organize model elements. |
| Use Case | Reused | Use Case Diagram | Capture system-level functions and interactions with actors. |
| Activity Diagram | Reused | Activity Diagram | Describe workflows and behaviors. |
| Sequence Diagram | Reused | Sequence Diagram | Describe interactions over time. |
| State Machine | Reused | State Machine Diagram | Describe states and transitions of components. |
| Timing Diagram | Reused | Timing Diagram | Show time-based behavior of components. |
| Interaction Overview | Reused | Interaction Overview | High-level view of interaction logic. |
| Deployment Diagram | Not included | — | UML-specific; SysML doesn’t use it. |
| SysML Diagram | Type | Purpose (1 sentence) |
|---|---|---|
| Requirements Diagram | New | Captures and links system requirements to design elements. |
| Parametric Diagram | New | Expresses mathematical constraints for analysis and engineering calculations. |
| Allocation Diagram | New | Shows relationships like “allocate function → hardware/software.” |
- Explain briefly:
- What is the Block Definition Diagram (BDD)?
- What are the main differences to the UML Class Diagram?
- Definition: Defines the building blocks of a system (hardware, software, physical parts), their properties, interfaces, and relationships.
- Differences to UML Class Diagram:
- Not tied to object-oriented concepts (no methods, visibility, inheritance semantics).
- Represents any system element, not just software classes.
- Supports physical flows, ports, and engineering properties.
- More flexible: blocks describe structure without OO rules.
- What is a Parametric Diagram in SysML?
How does it enhance system analysis compared to UML?
- Definition: Models mathematical constraints between system variables (e.g., forces, voltages, efficiencies).
- Advantage over UML: UML cannot express engineering equations; SysML parametrics allow analysis of performance, energy, stress, cost, etc., directly linked to system architecture.
- Create a BDD diagram focusing on the hardware components of a Tetris Cabinet (try to think of everyting).
- Create a UML Component diagram for the same Tetris Cabinet.
