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 was created because UML is too software-centric. SysML fills the gaps when you need to model hardware, mechanics, energy flows, sensors, and cross-disciplinary systems.
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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.