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What is SysML? - What You Need to Know

The SysML Forum is a web community dedicated to the Systems Modeling Language (SysML), the de facto standard architecture modeling language for Model-Based Systems Engineering (MBSE) applications across diverse industries, ranging from aerospace-defense and communications to automotive and medical devices. Since SysML is a popular dialect (technically a Profile) of UML v. 2, the industry standard for specifying software-intensive architectures, it is a popular choice as a lingua franca for MBSE teams that include both systems and software engineers.

Here you can find information related to SysML applications, as well as related topics such as SysML Tools, SysML Training, SysML Discussion Groups, SysML Example Tutorials, SysML Processes, and MBSE Processes that use SysML.

What is the Systems Modeling Language (SysML)?

Question Variant(s): What is SysML?; What is OMG SysML?
Definition

Systems Modeling Language (SysML): SysML is a general-purpose architecture modeling language for Systems Engineering applications.

  • SysML supports the specification, analysis, design, verification, and validation of a broad range of systems and systems-of-systems. These systems may include hardware, software, information, processes, personnel, and facilities.
  • SysML is a dialect of UML 2, and is defined as a UML 2 Profile. (A UML Profile is a UML dialect that customizes the language via three mechanisms: Stereotypes, Tagged Values, and Constraints.)
  • SysML is an enabling technology for Model-Based Systems Engineering (MBSE).

The SysML was originally created by the SysML Partners' SysML Open Source Specification Project in 2003. The SysML was adapted and adopted by the Object Management Group (OMG) as OMG SysML in 2006. For more information about the current version of OMG SysML, see the SysML FAQ: What is the current version of SysML?.

SysML Diagram Taxonomy for Agile MBSE™
SysML Diagram Taxonomy

The SysML is composed of nine (9) diagram types and Allocation Tables for mapping language elements across diagram types:

DIAGRAM PROPERTIES
EXECUTABLE SEMANTICS
FORMAL SEMANTICS
Diagram Name Diagram Type UML 2 Analog SDLC Usage Essential
AGILE SYSML?		 Dynamic
Sim †		 Math
Sim ‡		 Auto
Code
Gen		 Rigor Semi Informal
Requirement diagram (req) Static Structure
[Declarative]		 N/A Requirements Analysis
Use Case diagram (uc) Behavior *
[Non-Simulatable]		 Use Case Requirements Analysis
Activity diagram (act) Dynamic Behavior
[Simulatable]		 Activity
[minor mods]		 System Analysis,
Functional Analysis,
System Design
Sequence diagram (sd) Dynamic Behavior
[Simulatable]		 Sequence System Design
State Machine diagram (stm) Dynamic Behavior
[Simulatable]		 State Machine System Analysis,
System Design
Block Definition Diagram (bdd) Static Structure
[Black Box
Definition]		 Class
[moderate mods]		 System Analysis,
System Design
Internal Block Diagram (ibd) Static Structure
[White Box
Usage]		 Composite Structure
[moderate mods]		 System Analysis,
System Design
Parametric Diagram (par) Static Structure
[White Box
Usage]		 N/A System Analysis,
System Design
Package diagram (pkg) Static Structure
[Grouping]		 Package
[minor mods]		 All SDLC phases
Allocation Table N/A
[Relationship Matrix]		 N/A All SDLC phases

†: Dynamic Simulation (a.k.a. Dynamic System Simulation) refers to the capability of a computer program to execute the time-varying behavior of a system of interest. In general, with the exception of Use Case diagrams, SysML and UML 2 Behavior diagrams are potentially capable of Dynamic System Simulation.

‡: Mathematical Modeling & Simulation (a.k.a. Mathematical ModSim, Mathematical M&S, Parametric Simulation) refers to the capability of a computer program to execute the a mathematical model of the behavior of a system of interest, where the model is defined as a set of mathematical equations. When properly defined and applied, Parametric diagrams are capable of Mathematical ModSim; no other SysML or UML 2 diagrams are capable of this.

*: Although Use Case diagrams are generally classified as Behavior diagrams by both the OMG SysML and UML 2 specifications, their Behavioral semantics are ambiguous and incomplete. Whereas Activity, Sequence, and State Machine diagrams are Turing Complete and their dynamic behavior can be simulated or executed, Use Cases diagrams are not Turing Complete and are not simulatable.

What are the SysML diagram types?

Question Variant(s): How do the SysML diagrams compare and contrast?; What are SysML Allocation Tables and what are they used for?

The SysML is composed of nine (9) diagram types and Allocation Tables for mapping language elements across diagram types:

The SysML Diagram Taxonomy comparison table below explains the similaries and differences among the various SysML diagram types.

SysML Diagram Taxonomy for Agile MBSE™
SysML Diagram Taxonomy

The SysML is composed of nine (9) diagram types and Allocation Tables for mapping language elements across diagram types:

DIAGRAM PROPERTIES
EXECUTABLE SEMANTICS
FORMAL SEMANTICS
Diagram Name Diagram Type UML 2 Analog SDLC Usage Essential
AGILE SYSML?		 Dynamic
Sim †		 Math
Sim ‡		 Auto
Code
Gen		 Rigor Semi Informal
Requirement diagram (req) Static Structure
[Declarative]		 N/A Requirements Analysis
Use Case diagram (uc) Behavior *
[Non-Simulatable]		 Use Case Requirements Analysis
Activity diagram (act) Dynamic Behavior
[Simulatable]		 Activity
[minor mods]		 System Analysis,
Functional Analysis,
System Design
Sequence diagram (sd) Dynamic Behavior
[Simulatable]		 Sequence System Design
State Machine diagram (stm) Dynamic Behavior
[Simulatable]		 State Machine System Analysis,
System Design
Block Definition Diagram (bdd) Static Structure
[Black Box
Definition]		 Class
[moderate mods]		 System Analysis,
System Design
Internal Block Diagram (ibd) Static Structure
[White Box
Usage]		 Composite Structure
[moderate mods]		 System Analysis,
System Design
Parametric Diagram (par) Static Structure
[White Box
Usage]		 N/A System Analysis,
System Design
Package diagram (pkg) Static Structure
[Grouping]		 Package
[minor mods]		 All SDLC phases
Allocation Table N/A
[Relationship Matrix]		 N/A All SDLC phases

†: Dynamic Simulation (a.k.a. Dynamic System Simulation) refers to the capability of a computer program to execute the time-varying behavior of a system of interest. In general, with the exception of Use Case diagrams, SysML and UML 2 Behavior diagrams are potentially capable of Dynamic System Simulation.

‡: Mathematical Modeling & Simulation (a.k.a. Mathematical ModSim, Mathematical M&S, Parametric Simulation) refers to the capability of a computer program to execute the a mathematical model of the behavior of a system of interest, where the model is defined as a set of mathematical equations. When properly defined and applied, Parametric diagrams are capable of Mathematical ModSim; no other SysML or UML 2 diagrams are capable of this.

*: Although Use Case diagrams are generally classified as Behavior diagrams by both the OMG SysML and UML 2 specifications, their Behavioral semantics are ambiguous and incomplete. Whereas Activity, Sequence, and State Machine diagrams are Turing Complete and their dynamic behavior can be simulated or executed, Use Cases diagrams are not Turing Complete and are not simulatable.

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