SysML v2 FAQ: Answers from Tim Weilkiens, Stephan Roth & Uwe Kaufmann

In the last few weeks, there have been announcements on the "usual channels" that the current version of SysML v2 has been accepted by the OMG. Unfortunately, I could find surprisingly few details about what this actually means and how it will continue.

So I contacted the "usual suspects", from whom I received extremely helpful answers, which I would like to share here.

Update: Also check out this great SysML v2 FAQ by Gerd Wagner on LinkedIn

The usual suspects

Probably the best-known SysML v2 driver in German-speaking countries is Tim Weilkinswho also leads the SysML v2 working group for the OMG. Tim also gave me the most important information about the meeting in brief. The Object Management Group (OMG) is actually a very open group that makes information accessible without barriers. However, this does not mean that it engages in excessive marketing.

Unfortunately, the OMG is always somewhat reticent when it comes to providing official information about what happened at the meeting.

Tim Weilkiens

Unfortunately, we were unable to find a meeting at short notice. Tim referred me to Uwe Kaufmann and Stephan Roth, both of whom are also actively involved in the SysML v2 standardization process.

I had a long conversation with Uwe online. Uwe has been involved in various consortia for a long time and already gave an interview published here in 2019 to SysML v2. He is currently also heavily involved in SpecIFa convention for the semantics of system models.

I met Stephan at this year's ReConfwhere he gave a presentation on SysML v2. He has also been involved with the OMG for many years and, like Tim, is a member of oose active.

In addition to the people mentioned here, there are of course many more, especially outside Germany. The best known is probably Sandy Friedenthal be. Further down I have embedded an interview with Sandy.

In the following I have summarized the collected information as FAQ:

What is SysML anyway?

The Systems Modeling Language (OMG SysML) is a graphical, standardized modeling language based on UML 2. It is used in the field of systems engineering for modeling various complex systems

Wikipedia

Most readers probably already know what SysML is (Here is a series of articles on the topic in this blog). It is important to note that although SysML is graphical, the diagrams are only a view of the system. "Painting" is not the same as "modeling".

What are the most important differences to SysML 1.x?

No UML dependencies: The biggest difference is certainly the substructure. SysML was initially an "extended intersection" of UML. Some model elements were omitted, others added, others varied. However, this did not change the fact that the (formal) substructure of the language has dependencies on UML. This is no longer the case with the new version. Furthermore, the underlying language (KerML, see below) is based on formal semantics.

Use before definition: There are two versions of (almost) all model elements: "Usage" and "Definition". However, it is important for use that the definition is optional, which can simplify and speed up modeling.

Textual notation: In addition to the graphical notation, SysML v2 introduces a textual notation.

API: The standard defines an interface (API) with which we can interact with the model. This makes many new use cases possible. In particular, it drastically simplifies integration.

Where can I find the standards and how much do they cost?

In contrast to other organizations (such as ISO), the OMG makes all standards available free of charge. With regard to SysML, however, there is only SysML v1.x to find. For the work on version 2, the working group has used the gitHub repository Systems modeling set up. There we not only find the standard documents, but also many other documents, such as presentations and even a reference implementation.

What does the new substructure look like?

Surprise! There is not just one new standard, but several. The corresponding documents from the gitHub systems modeling repository I have linked directly here:

KerML - The Kernel Modeling Language (KerML) offers an application-independent syntax and semantics for creating more specific modeling languages. SysML v2 is just one of these, and others could be added. KerML is still based on formal semantics (First Order Logic). As a result

It is conceivable that a UML v3, if it should exist, could also be based on KerML.

Stephan Roth

SysML - SysML has now been specified on the basis of KerML.

SysML API - There is also a separate specification for the API.

There is also a document for the Transformation from SysML v1 to v2which, however, is primarily of interest to tool manufacturers.

What exactly does the acceptance of SysML v2 by the OMG mean?

Acceptance does not mean that the standard is official (see next question).

The development of an OMG standard takes place in several phases, including the submission of proposals, review by the technical committee, public review and voting by the OMG members. Once the specification has gone through all these stages and the final version has been approved, it is considered completed. Acceptance is the last step before finalization.

At the end of the meeting in March 2023, three Finalization Task Forces (FTF) were established to finalize the future standards (KerML, SysML and API). The tasks of the FTF include resolving any remaining issues and ensuring that the specification is coherent and complete. The FTF may also make additional changes to the specification if required based on feedback received during the review process.

When will SysML v2 become an official OMG standard?

It takes a maximum of two years from acceptance to official standardization. During this time, the Finalization Taskforce works on completing the standard. The timeline is tough. This means that standardization must be completed by Q1 2025 at the latest. Tim, Stephan and Uwe expect it to be mid-2024.

Who is the driver behind SysML v2?

This is a complex question. One driver is certainly the increasing complexity of systems. Many features of SysML v2 make it possible to master complexity in a way that is not possible with SysML v1. This is due, for example, to the "softened" formalism of v1 (no consistent formal semantics), or the less strict separation between definition and use.

On the commercial side, the Defense industry the drivermore than any other industry.

When will tools support SysML v2?

Almost all major tool manufacturers are planning (at least officially) to quickly support SysML v2. Furthermore, there is already a open source reference implementation.

Personally, I am always a little cautious here. More than once I have seen a tool manufacturer say that "Standard X" is supported, but then it turned out to be more marketing lip service (minimal but not practical). How quickly the tools will be ready for practical use probably depends on the pressure that customers exert.

Which question is missing?

There are certainly many more questions about SysML v2. If an important question is missing or if there are any errors, please let me know. I plan to continue updating this FAQ.

Photo by Ugo Mendes Donelli on Unsplash