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How to work around the lack of SysML diagram frames? [message #1768518]

Wed, 19 July 2017 12:13

Eclipse User

Hello--
There are several posts already requesting SysML diagram frames, but I would like to hear from people who use Papyrus for SysML modeling as to favored work-arounds in situations where the frame is an integral part of the diagram. Specifically:

--constraint parameters placed on PAR diagram frames
--ports/flows placed on IBD frames
--activity parameters places on ACT diagram frames

In my understanding of SysML, the diagram frame represents the top-level model element of the diagram, so I just can't see how one gets by without frames. How do you guys do it?

Thanks in advance for any wisdom shared!

Re: How to work around the lack of SysML diagram frames? [message #1768758 is a reply to message #1768518]

Sun, 23 July 2017 12:53

Eclipse User

What is the semantic of a diagram frame?

I my point of view despite the fact a diagram visualizes elements of a model, a diagram is not an element of the model. Consequently in my opinion it does not make sense at all to place constraints, ports, etc on a diagram frame.

And I feel my opinion backed by the fact diagrams are not defined as UML Metaclasses in the UML 2.5 abstract syntax specification (http://www.omg.org/spec/UML/20131001/UML.xmi), the fact ANNEX A and B of the UML 2.5 specification (http://www.omg.org/spec/UML/2.5/PDF) and also ANNEX B of the SysML 1.4 specification (http://www.omg.org/spec/SysML/1.4/PDF) abstract syntax specification and diagrams are distinguished. I just need to cite the first sentence of ANNEX A of the UML 2.5 specification: "This annex describes the general properties of UML diagrams and how they relate to a UML (repository) model and to elements of this.".

Written this I can ask more specific: What is the semantic of a diagram being an element outside the model in the context of the model?

The SysML specification circumvents this issue by referencing the model element the diagram border represents by the element's name. But this reference is not guarantied to be unique. In UML-- SysML is an UML profile -- a package is defined to be a name space. As a result elements of the same name and type are allowed to co-exist in different packages of a single model.

Tools like IBM Rational Rhapsody or Sparx Enterprise Architect work around this problem by forcing the diagram to be a child [element] of the element it represents.

All this in my opinion the SysML approach of making diagram borders proxies of model elements violates IMHO the engineering rule of separation of concerns. For me this approach is bad style engineering.

I prefer using the model elements themselves rather than proxies and feel this as the way it should be.

[Updated on: Sun, 23 July 2017 15:07] by Moderator

Re: How to work around the lack of SysML diagram frames? [message #1768791 is a reply to message #1768758]

Sun, 23 July 2017 19:52

Eclipse User

Thank you Carsten! Your reply both answered my question, and spoke to some of the underlying confusion I've felt on this point as I've studied SysML. It seems that, at the very least, your approach would be easier for the uninitiated to understand.

To be ultra-concrete, I've attached an image taken from the book A Practical Guide to SysML, which show an ibd of a block called Camera with a port (shown on the frame) called boundary: Light Interface. How would you communicate the same information about the usage of the port on this block?

Thanks again!

index.php/fa/30088/0/

Attachment: Port on ibd frame.png
(Size: 60.42KB, Downloaded 1318 times)

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