Geometry Examples: CarWithShapeAndCSG.sysml [WITH EXPANDED DISCUSSION]

Practical modelling concerns are critical for the uptake of SysMLv2, and this topic is very important to me professionally.

In some of the diagrams in this slide trail (and in the Webel SysMLv2 course) including some of the supporting SysMLv2 machinery was educationally helpful (including also relationships from the user model elements to metaclasses and such); here, with this quite complex modelling target, it is not so effective.

Indeed, even the more "minimal" upper diagram is a lot of information for non-SysMLv2 fluent stakeholders to take in, and unfortunately, because AFAICT Cameo 2026xHF2 does not have a compartment for listing basic refs on symbols, one has to use symbols in cases where simply listing the element along with any feature values would suffice and be more concise.

The lower diagram also includes some tips on how one might Divide & Conquer it, including:

• Use mostly compartments (but does not work with basic refs in Cameo)
• Use separate Views for different aspects.
• If you want to explore relationships to specific metaclass of model library elements use separate dedicated non-stakeholder Views.

It's okay to have some diagrams that sprawl during your own modelling (for yourself) but take some time to Divide & Conquer them before presenting them to other colleagues.

Prefer Black-on-White with colours only for special highlighting!

If you've every attended a Webel SysML course or you've seen any of the online tutorials for SysML, you'll know that I am a HUGE fan of just using black and white styles (no MagicDraw or Cameo colours) and only using colours for special highlights, such as my favourites blue or magenta for symbol outlines.

That said, not everyone is such a fan of magenta (or may have some irrational fear of things that a "pinkish") but blue and magenta work brilliantly together for contrast.

In any case, overuse of colours is a Modelling Anti-Pattern. One quickly runs out of distinguishing colours, and it undermines the effectiveness of using the widely recognised orange for warnings and red for errors or bugs.

And it can also exclude readers with Colour Deficiency Conditions).

If you have lots of relationships it can be useful to use coloured lines to distinguish their roles (as shown in the lower diagram, which without that would be almost impossible to discern). But then you might be better off adopting a more SysMLv2-friendly compartment oriented approach (see below).

If you find yourself using lots of different colours it's often a hint to Divide & Conquer using separate views of different aspects of the same system!

BTW Most Webel SysMLv2 slides use a different colour policy for KerML metaclasses and SysMLv2 metamodel elements to distinguish them:

Did you know? Dr Darren, who swears by Black-on-White for most SysML diagrams, just loves colourful Light Art & Flower Photography and makes beautiful colourful Maths Art using Mathematica (mostly) and Blender. Just DO switch off the default "Cameo colours" and use Black-on-White for SysML, and then a little colour used for special highlighting has some contrast.

The trend in SysMLv2 is to more compartment oriented representations

For those of use who have used SysML for decades, strongly associative modelling is not only easy to read, it offers some very powerful capabilities that a more "text like" or "code like" approach cannot. But not everyone has used SysML for decades.

In the Webel SysMLv2 course slides a decision was made to mostly indeed use associate modelling with relationships, in order for students to become more familiar with the relationships.

But the wider industry trend is towards more code-like representations, perhaps in part because SysMv2 itself now has a textual representation code.

Learn about modelling best practices for SysMLv2 in Cameo from Webel!