Understanding the ecosystem of MBSE, SysML, and TOGAF
My exploration of complex system development has led me to examine the relationship between several key frameworks and methodologies: Model-Based Systems Engineering (MBSE), the Systems Modeling Language (SysML), and The Open Group Architecture Framework (TOGAF). While it can be tempting to see them as a simple hierarchy, their interactions are more interconnected.
This post synthesises how these concepts fit together, not as layers in a stack, but as distinct, complementary functions within the broader challenge of managing complex systems.
Defining their distinct roles
The most effective way to understand these concepts is to see them as functions with different scopes, all operating within the same ecosystem.
- Systems Engineering (SE) is the overarching discipline. It is the holistic, lifecycle-spanning process for managing the technical development of a system.
- TOGAF provides the enterprise context. It is a framework that helps an organisation align its technology strategy with its business goals, guiding which systems should be built and how they fit together.
- MBSE is a relatively new methodology for executing systems engineering. It is a specific way of doing SE that uses models instead of documents as the primary artefact.
- SysML is the language used to implement the MBSE methodology. It provides the standard notation for creating the models.
Let’s break down each of these roles.
Systems engineering: The overarching discipline
As I explored in my previous posts on core SE concepts and the journey from design to disposal, systems engineering is the discipline that brings structure to complexity. It is a formal process that covers the entire system lifecycle, from defining needs and requirements to design, verification, operation, and retirement.
It is not a single layer but the entire project-level framework. The master plan for this effort is often captured in a Systems Engineering Management Plan (SEMP), which outlines all the technical activities required to deliver the system.
TOGAF: The enterprise context
TOGAF operates at the level above a single project. It helps an organisation answer strategic questions like, “What capabilities do we need to achieve our business objectives?” and “How should our portfolio of systems evolve to provide these capabilities?”
It provides the governance and architectural vision that ensures individual projects, each run using systems engineering principles, are not just successful in isolation but also contribute to the broader enterprise strategy. In essence, TOGAF sets the stage and defines the “why” for a project, while SE manages the “how” for that specific project.
MBSE: A modern approach to systems engineering
MBSE is not a separate discipline from SE; it is an evolution of it. Where traditional systems engineering often relied on a vast collection of documents (specifications, interface control documents, test plans), MBSE centralises this information into a single, interconnected digital model.
Adopting MBSE is more than implementing new tools; it’s about transforming your organization’s approach to systems engineering.
— specinnovations.com
It is a methodological choice. A team applies the discipline of systems engineering by using a model-based approach. This brings benefits like improved consistency, better change management, and clearer communication.
SysML: The language of MBSE
If you choose the MBSE methodology, you need a language to build your models. SysML is the industry standard for this. It provides a precise, graphical notation for defining a system’s structure, behaviour, requirements, and parameters. It is the technical tool that makes the MBSE methodology practical.
How they work together in practice
Imagine a large energy company wants to improve its grid management.
- TOGAF (Enterprise Context): The enterprise architecture team uses TOGAF to analyse business drivers (e.g., renewable energy integration, cost reduction). They identify a need for a new, intelligent grid management system and define its high-level requirements and how it must interface with other enterprise systems.
- Systems Engineering (The Discipline): A project is launched to build this new system. The project is governed by SE principles, documented in a SEMP. This plan outlines the entire lifecycle, including requirements management, design reviews (PDR, CDR), risk management, and its Verification and Validation (V&V) strategy. This strategy ensures the team continuously checks that they are building the system correctly (verification) and building the correct system that meets the user’s needs (validation).
- MBSE (The Methodology): The project team decides to use an MBSE approach to manage the system’s complexity. Instead of writing a multitude of separate documents, they will build a comprehensive system model.
- SysML (The Language): The engineers use SysML to create the model in a tool like Cameo or Enterprise Architect. They use SysML diagrams to capture stakeholder requirements, define the system’s architecture, model its behaviour, and trace everything from end to end.
Benefits of a model-based approach
Choosing to implement SE principles via an MBSE methodology offers several advantages:
- Improved Communication: A unified model becomes the single source of truth, breaking down silos between teams.
- Reduced Risk and Cost: Virtual simulation allows engineers to identify design flaws early, before expensive physical prototypes are built.
- Guaranteed Traceability: MBSE provides clear, end-to-end traceability from requirements through to design and testing.
- Supports Sustainability: It allows for the optimisation of product design to reduce waste and improve resource efficiency.
In the end, everything connects back to the core discipline of systems engineering. As I have explored in my earlier posts, it provides the structured, lifecycle-focused approach needed to manage complexity. Frameworks like TOGAF and methodologies like MBSE, powered by languages such as SysML, represent the evolution of the systems engineering toolkit. They provide engineers with increasingly sophisticated capabilities to manage complexity with greater precision and clarity. As the systems we build become more interconnected and ambitious, the continuous improvement of our engineering tools is what allows us to tackle these challenges, ensuring we not only build the system right, but also build the right system.
