Broadcast date: December 2nd, 2021

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Welcome to the 2nd door of our MBSE Podcast Advent Calendar. Behind this door, we describe the system idea and system objectives.

The system idea is the elevator pitch of the system of interest. It briefly and crisply describes what the system is, with a special focus on what makes it special. It is text and provided with graphics if needed.

The SysML language does not know the concept of system idea. Interestingly, SysML does not know the concept of a system either, although it is a Systems Modeling Language. We can teach the language new concepts via the “profiles and stereotypes” extension mechanism. Behind one of the following doors, there will be an explicit explanation about this as well. Here in a nutshell: SYSMOD introduces the concept of a system via a stereotype – specialized from the block – and defines the system idea as a property of it.

In the model, it can then be represented like this. It is a tool-specific property that the text can be formatted. If graphics are part of the system idea, they are referenced.

The system idea of our Christmas tree is as follows:

System Idea in a Diagram

System objectives are also a concept that SysML does not recognize. SYSMOD again uses a stereotype to include it in the language. A system goal is a special form of the SysML requirement.

The following requirements diagram shows the objectives of our Christmas tree:

System Objectives in a Diagram

The diagram is illustrative, but the topology of the elements doesn’t really matter much here. It is a good practice instead to manage the model information in tables. This saves a lot of modeling effort. In addition, in today’s modeling tools, tables are usually model queries, i.e., they show all elements in the model. In the diagram, there are only the elements that a modeler has placed manually.

If needed, the diagram can be created quickly, for example, for a workshop.

System Objectives in a Table

You may have noticed the stakeholder. System objectives have a trace relationship to the stakeholders who are responsible for the goal. Here it is we podcast hosts, as we are responsible for the overall system.

SysML knows the concept of a stakeholder. SYSMOD nevertheless defines a stereotype “extendedStakeholder” to add special properties like contact or a priority.

Since the stakeholders are also related to the requirements and they also belong there thematically, they are stored in the requirements package in the model. You could represent them in a diagram, but it is much more practical in tabular form.

The table does not show all properties of the stakeholders but only the name, documentation, contact information, and priority.

Stakeholders in a Table

So much for the second door of our MBSE Podcast Advent Calendar. We wish you a great 2nd of December.

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