Entity sets - containment and parent-child

[Tim Tautges]

Mark Beall wrote:
> 
>>
>> Here's an example:  Suppose you're doing swapping, or any other 
>> topological modification to a mesh.  Chances are excellent that you 
>> only want to do the 2-2 swap on the surface if both surface faces 
>> classify on the same model face.  Now, if you've got an entity-entity 
>> relation giving you classification, that's an easy test.  On the other 
>> hand, if you've got a geometric entity-mesh set relation, you have to 
>> find out which set a mesh face is in, which can only be done through 
>> an exhaustive search of faces.  So the higher memory (e-e) relation is 
>> much lower CPU.
> 
> Right, sorry, I was thinking about the entity sets in the wrong way 
> (somehow my brain was thinking that the switch_order argument would 
> magically do this, but that's not what it does).
> 
> So then createAssociation(model,mesh) should create a entity-set 
> relation and createAssociation(mesh,model) should create a different 
> entity-entity relation. Of course, in our implementation, these are 
> really just things that are pretending to be relations and entity sets, 
> but that doesn't really matter.

Note that as currently spec'd, relations are two-way, so I suspect having a mesh/geometry entity/entity-type relation 
wouldn't be much good, since each geometry entity would only be related to one mesh entity (which couldn't be an entity 
set, since those are different things in the iMesh interface).

- tim

> 
> If that's the case, it would seem you just need to ask for the right 
> relation, not necessarily be able to change them from one type to 
> another (in this case it's pretty equivalent, maybe not in other cases 
> that I haven't thought of).
> 
> mark
> 
> 

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              Tim Tautges            Argonne National Laboratory
          (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
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