[SysML Forum] Trying to model a functional hierarchy

[Sultan Hashmi]

I'm trying to build and show a functional hierarchy where it is easy to see how higher level functions break down into more granular functions. I'm using Cameo Systems Modeler with SysML

Two ideas pop into my mind immediately to handle this:

1. Using a bdd, and then just creating directed composition and aggregation relationships to create a hierarchy. Issue with that: Then if you ever want to flesh out a flow of sorts of higher level activity, that contains the lower level functions, you have to create new usages of those functions which have no relation to composition/aggregation relationships you've made. So you might end up with duplicate relationships
   
2. Using an activity diagram to populate the activities with other actions recursively. Horrible for visualization, but you can create a relation map going from activity, that then draws a line to activities that it has call behavior actions included in its own activity diagram and so on. However, this can be a tedious process that engineers will not buy into. Also, relation maps are incredibly glitchy and you really can't get a customizable/flexible tree structure this way.
   

I was wondering if I could get some guidance from the SysML community on this.

Thanks
Sultan Hashmi

[Stephan Roth]

Hi Sultan,

there is a little known "built-in feature" in SysML that allows to depict the call hierarchy of activities, i.e., that CallBehaviorActions are calling Activities, as an activity tree. Tim Weilkiens wrote a blog article about this some time ago: https://mbse4u.com/2012/09/10/hidden-feature-of-sysml-activity-trees/

Maybe that's what you're looking for?

Hope that helps!

Cheers,

Stephan

[James Towers]

Option 2 is the way to go. 

As you point out Cameo can use an Activity to draw a built-in Activity Decomposition Map, which is generated dynamically.

Additionally there’s a wizard which will generate a BDD from an activity, showing activities with rectangular symbols and composition relationships between them (option 1). This however isn’t dynamic so you will have to re-run the wizard manually if there are any changes.

So, choose option 2 and get option 1 for free!

Not sure about the “engineers won’t buy into this” comment. Obviously engineers who aren’t competent in SysML won’t, but then why would you try to do MBSE without having the proper skills?

You could try to avoid this by creating the required structure in a table, in Excel and importing or using a product like MapleMBSE

I’ve never had any problems with relation maps, so can’t comment on that. Creating custom maps is relatively advanced, but that’s mainly due to the complexity of the meta-model. 

Sent from my iPhone

On 7 Feb 2021, at 21:20, 'Sultan Hashmi' via SysML Forum <sysml...@googlegroups.com> wrote:



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