SysML

Homework: From UML to SysML

Topic: Understanding SysML through comparison with UML
Due: Nov. 19, 2025
Submission: A single pull request with all your contributions.

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Part 1: Conceptual Questions

Answer briefly

1. Purpose and Motivation
   Why was SysML created? What limitations of UML does it address?

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

3. 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. While classes consist of fields, methods and references, blocks consist of properties, references/values and ports.

5. 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.

6. 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.

For example if I want to develop an autonomous drone, I couldn’t make a UML diagram because I wouldn't have blocks like the physical components, the analysis of the parametrics, the physical quantities. This couldn't be modeled with UML, because it is more for a software example, and the architecture of the model wouldn't be enough.

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Part 2: Diagrams

1. 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.
Object Diagram	Modified	Block Definition Diagrams (BDD)	Shows a snapshot of the objects/instances in a system at a specific point in time.
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-Only Diagrams

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.”

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2. 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 (structure).
• 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.

3. 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) and explains how system parameters relate to each other.
• Advantage over UML: UML cannot express engineering equations; SysML parametrics allow analysis of performance, energy, stress, cost, failure probability, power budgets, thermal loads, etc., directly linked to system architecture.

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Part 3: Examples

1. Create a BDD diagram focusing on the hardware components of a Tetris Cabinet (try to think of everyting).

2. Create a UML Component diagram for the same Tetris Cabinet.