Re: [SysML Forum] AggregationKind::[shared|composite]

[James Towers]

Hard to say. One formal constraint of composition is that the upper bound of the multiplicity at the ‘whole’ end can’t exceed 1. This means that (proving the multiplicity is 0..1) an instance of a part can be removed from an instance of a  whole, can exist independently of the whole and can be added to another instance of a whole (if required).  However, an instance of a part can only belong to (at most) one instance of a whole at any one time. 

Do you require instances of your ‘entity’ to exist in multiple contexts at the same time? i.e. are the contexts overlapping?

On 24 Jul 2022, at 18:21, gashu...@gmail.com <gashu...@gmail.com> wrote:

Should an Association’s AggregationKind be “shared” or “composite“ when the relationship between the aggregate (e.g., a whole, a collection), when the aggregate represents a context (e.g., a simulation, a situation) not an [Item|Entity], and the part(s) (e.g., member(s) of the context, situation, simulation) whose life time(s) is/are NOT dependent on the life time of the aggregate?  I argue the AggregationKind SHOULD be “shared”.  The OMG’s “Risk Analysis and Assessment Modeling Language (RAAML) uses “composite” in its examples when given the aforementioned.  I argue that “composite” explicitly asserts “Parthood” of the related model element to the aggregate model element.  In the case of the aggregate representing a context (e.g., analysis, simulation, situation) AggregationKind should be “shared’; as all of these contexts explicitly represent collections of entities having a membership in the collection with each being independent of the aggregate’s life time.

 

Other’s insights?

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