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Question about Nested Parts

Chandan Mathur

Hello All, first time posting here.  

I've attempted to attach an image, but not sure if it worked.

I'm using Cameo v19, SP4 and SysML

A very simple BDD

  1. Door block composed of a Window block
  2. A Car block with two compositions to the Door block named door1 and door2.  Two compositions so I can refer to each Door part individually.
  3. I create an IBD for Car and display the two Door parts, door1 and door2.
  4. I then display the parts within door1 and door2
  5. As expected, i see a Window part in each Door part
  6. But, unexpectedly, the Window part is the same model object for both Door parts.  It has the same element ID.  I would have expected to see a different Window parts for each Door.

How should i structure my BDD so that each Door has its own, unique Window part?

thank you, 

Chandan

 

 

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  • Chandon,

    You have defined only 1 definition of «block» Door and «block» Window in your model. The «block» Door has a single Usage of the «block» Window as a part property. No matter how many usages (aka: Composite Association) of the «block» Door the «block» Car has, the Window usage by the Door is always the same part property. “Usage” as a part property, is in essence, an “instance” of the “Definition” of the Block which defines the part property.

    The semantics of this model asserts that the «block» Door ALWAYS has the same properties. If that is not true, then you need to create unique definitions of Door and Window in the model.

    I’d like to suggest 2 papers by Conrad Bock that may more completely illuminate this issue for you.

    1) UML 2 Composition Model &
    2) Componentization in the Systems Modeling Language

    Regards,
    Geoff
  • in reply to Geoffrey Shuebrook
    Geoff is correct. I don't often use instances...and if the doors are really different (LH/RH, for example), you should make a LH Door and RH Door block (with LH and RH Windows, respectively). It depends upon how you want to structure your model.
    I'd also ask you to consider what you're trying to do...I find BDDs are often misused to show things that are better represented in a table, matrix, or relation map...or IBD, for that matter.
    Focus on getting the containment tree (model) right and the rest will flow naturally!
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  • in reply to Geoffrey Shuebrook
    Geoff is correct. I don't often use instances...and if the doors are really different (LH/RH, for example), you should make a LH Door and RH Door block (with LH and RH Windows, respectively). It depends upon how you want to structure your model.
    I'd also ask you to consider what you're trying to do...I find BDDs are often misused to show things that are better represented in a table, matrix, or relation map...or IBD, for that matter.
    Focus on getting the containment tree (model) right and the rest will flow naturally!
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