Modeling with ARCADIA as a method and Capella as a tool during a bid

Today's article was written by Michael Schäfer. Michael has been Lead System Architect at Thales Germany since 1992, is a Certified System Engineering Professional (CSEP) and is an expert on modeling in the rail industry. Michael writes and speaks a lot about the open source modeling tool Capella, as well as the associated development methodology ARCADIA. In this guest post, he describes how Capella modeling has already been successfully used in the bidding phase.

When to model?

Modeling in the bidding phase of a project? If someone had asked me a good year ago whether this made sense, I would have looked at them rather doubtfully. As a system architect who manages larger and smaller projects in the field of control and safety systems for railroad operations, I had always seen model-based system architecture in the project phase. Models should and should provide a good basis for the developers and define the requirements for them in such a way that the context is also understandable.

But then I was asked to help with an offer that had me laughing at all the things I knew from the days when model-based working was introduced:

• "Babylonian linguistic confusion." Due to the history of rail operations, each country has its own terms and the manufacturers use different expressions. This was also reflected in the tender documents.
• Technical diagrams, created with various tools, inhomogeneous in presentation, content and granularity.

The diagrams in particular gave the impression that the teams involved did not communicate enough with each other: different color meanings, very different representations (from images with detailed network components to abstract block diagrams). The mixing of logical views with physical aspects was quite typical. At one point, the author of the image considered a physical aspect to be important, so he simply incorporated a radio link into an otherwise abstract communication diagram... I think many readers will recognize images like this.

Modeling essential elements

But it is precisely at this point that ARCADIA as a methodology and Capella as the associated tool to get these problems under control. Even though these approaches offer many more possibilities, we concentrated on the essential points during the offer phase:

• Representation of the (component) architecture and all external communication partners (as actuators) at the logical architecture level
• Representation of the physical architecture (including a simplified deployment of the SW) at the physical architecture level
• In some critical cases, we have modeled the data flow and a rough function distribution on this basis

Important results were, for example: In the physical architecture, it was possible to specify as a property of a model element whether this element is part of the delivery or is provided by the customer. As we were then able to display this in different colors, we had a good basis for discussion with the customer. Furthermore, we were able to infect missing components in some places that had been lost due to the mixture of logical and physical architecture.

Of course, there are still challenges: You shouldn't underestimate the time it takes to implement a proposal, which is why we were only able to partially model the distribution of functions, for example. You also encounter the type of employee who loves their familiar drawing tools even more in proposal teams than in development teams: "What, I'm not allowed to create architectural images with my presentation program? Can people even read your cryptic images?" However, it turned out that if the images were processed a little graphically, the customer could also understand them quite well. That was another reason why we won the contract in the end.

Hello World!

For some readers, this type of modeling may seem more like a "Hello World example", but it has helped us: Despite having only relatively few diagrams (compared to a development project), it resulted in a uniform representation and methodology. Even if you can achieve a lot at this size without a modeling tool, the methodology and the tools lead the team to a more uniform way of working, which also makes work easier, especially in the hectic bidding phase.

If anyone wants to see and hear this in more detail, here is the webinar:

Cover photo from Clem Onojeghuo on Unsplash
Diagram by Michael Schäfer