Systems Modeling Language (SysML)

The Systems Modeling Language (SysML) is a general-purpose modeling language for systems engineering. It is an Object Management Group (OMG) standard, developed jointly with the International Council on Systems Engineering (INCOSE), for specifying, analyzing, designing, and verifying systems that may include hardware, software, information, processes, personnel, and facilities.

SysML is defined as an extension of a subset of the Unified Modeling Language (UML). It reuses seven of UML’s diagram kinds and drops the diagrams that are software-centric, such as object, communication, deployment, component, composite structure, and timing diagrams. Two new diagram kinds are added for systems engineering work: the requirement diagram, which captures requirements and their relationships to the parts of the system that satisfy, verify, or derive them, and the parametric diagram, which expresses quantitative constraints for performance and other engineering analyses. The result is a smaller language than UML, with nine diagram types in all.

The central structural concept in SysML is the block, a more general unit than UML’s class. Blocks model any system element — a physical component, a software subsystem, a person, a facility — and the relationships between them. Block definition diagrams describe the structure of blocks and their relationships, while internal block diagrams show the parts and connections internal to a single block.

History

The SysML initiative began in January 2001, when an INCOSE working group on model-driven systems design decided to customize UML for systems engineering. INCOSE and OMG jointly chartered a Systems Engineering Domain Special Interest Group later that year, with the ISO AP 233 workgroup also contributing. The SysML Partners, an open source specification team led by Cris Kobryn, produced the first draft (v0.9) in January 2005, and the v1.0 alpha followed in November 2005.

OMG adopted SysML in July 2006 and issued the v1.0 specification as an Available Specification in September 2007. The line continued through v1.6, issued in November 2019. SysML was also published by the International Organization for Standardization as ISO/IEC 19514:2017.

A Request for Proposals for SysML v2 was issued by OMG in December 2017, alongside a parallel RFP for a v2 API and services. OMG approved final adoption of SysML v2.0 in July 2025 and published the specification in September 2025. SysML v2 is a substantial redesign. It replaces the UML-profile foundation of v1 with a new metamodel, and it specifies both a textual notation and a graphical notation, where v1 was graphical only. The textual notation aims to make models easier to author, diff, and manipulate programmatically.

Use in model-based systems engineering

SysML is the dominant modeling language for model-based systems engineering (MBSE), the practice of making a formal model of the system the shared reference artifact throughout its lifecycle — analysis, design, implementation, verification, and validation. The requirement diagram in particular supports requirements engineering by capturing functional, performance, and interface requirements in the same model as the design, and by recording traceability relationships between requirements and the blocks that realize or test them. This is a notable contrast with the conventional split between a system requirements specification (SRS) document and a separate design.

Because SysML is itself a UML profile in v1, other OMG profiles can sit on top of it. The Risk Analysis and Assessment Modeling Language (RAAML) is published as a SysML profile for safety, reliability, and security analyses, and is most relevant to teams building safety-critical systems where structured analyses must be maintained alongside the design.

Relationship to other OMG modeling standards

SysML is one of a family of modeling standards maintained by OMG. Its parent language, UML, is oriented toward the design of software systems. Model-driven architecture (MDA) is the OMG’s framework for deriving implementations from UML models through transformations, and is concerned with software platforms rather than whole engineered systems. SysML complements these by addressing the system as a whole, including its non-software parts and the engineering analyses that constrain them. Models are exchanged between tools using OMG’s XML Metadata Interchange (XMI) standard.

See also

References

  • Object Management Group (2007). OMG Systems Modeling Language (OMG SysML) v1.0. https://www.omg.org/spec/SysML/1.0/
  • International Organization for Standardization (2017). ISO/IEC 19514:2017 — Information technology — Object management group systems modeling language.
  • Balmelli, L. (2007). An Overview of the Systems Modeling Language for Products and Systems Development. Journal of Object Technology, vol. 6, no. 6, pp. 149–177.