There’s been a lot of debate in the systems engineering community about what model-based systems engineering means. We have given several presentations on the subject and there are a number of on-going LinkedIn threads. To some drawings are sufficient as a model. To others, including us, model-based systems engineering should be based on data or language elements, not just drawings. Obviously drawings are important as they provide a means of expressing the language elements visibly, which should enhance understanding.
In the last few blog articles in this series, we have taken an in-depth look at what a model is and what it means to systems engineering. This week we will discuss the current definition of model-based systems engineering and if we need a better definition.
The common definition to use is from INCOSE (International Council of Systems Engineering).
“Model-based systems engineering (MBSE) is the formalized application of modeling to support system requirements, design, analysis, verification and validation, beginning in the conceptual design phase and continuing throughout development and later life cycle phases.” – INCOSE
What the Definition Tells Us
By this definition, MBSE has been around for a long time – ever since someone drew the first flowchart. However, this is not how many of us generally refer to model-based systems engineering. The first time we heard the term, it was in conjunction with the RDD-100 tool. RDD-100 was based on an ontology derived from work TRW performed for the aerospace community in the late 1960s and 70s. More recently it has come to mean a way to capture the essential elements of information in a database and then visualize that information in many different ways, including the production of the many SE documents needed (plans, specifications, risk reports, etc.).
By the use of the term MBSE above, we would not expect a “language” of diagrams to meet this idea. However, today many systems engineers equate SysML with MBSE. We disagree, so we think a better definition for MBSE than the one INCOSE uses today is in order.
The lack of an ontology in SysML drove the Lifecycle Modeling Language (LML) Steering Committee to develop its specification (see www.lifecyclemodeling.org for more information). The Innoslate® tool was built to instantiate LML and has been extended to support other languages, including SysML. SPEC Innovations and many in the academic community are using this tool to explore other domains to provide better support to those domains using MBSE.
Do We Need a Better Definition?
Perhaps many feel we don’t need to change the INCOSE definition, but we at least need a better understanding of what we should do:
- We need to capture all the lifecycle information that describes a system in a database
- The database must support all systems engineering processes, including requirements, design, analysis, verification and validation
- Information contained in the database can then be consistently visualized, reviewed, validated, and reported on by the database tool
If we decide to create a better definition of MBSE, the bullets above could form the basis for this. In either case, let’s make sure that we SE practitioners provide better products, faster and cheaper, to enhance our value to the entire lifecycle.