[vo-dml] Clarification on composition rule..

[Laurent MICHEL]

Hello,

I follow the Pat's point of view.
I never really get the deep justification of not using open-ended 
multiplicities, or more accurately, I've never really understood how the 
conflicts between this rule (maxOccus = -1 discouraged) and the real 
world (camera pixels, polynonial functions, polygons..) are conceptually 
resolved.
Anyway, the fact that this discussion arises from time to time shows 
that the question is still relevant.

I think that using this feature is the responsibility of the modeler and 
the standard should not give more than a simple advice on this point, 
not a red flashing warning.
We can assume that a modeler describing polygons as an open-ended array 
of coefficients won't expect to have those coefficients individually 
stored in a any DB. From another hand, if he/she want to expose those 
coefficients as individual values, he/she will use another pattern on 
purpose.

Laurent

Le 09/03/2020 à 15:42, Patrick Dowler a écrit :
> As you may know, I don't let the warning from vo-dml validation about 
> open ended multiplicity bother me too much. Polynomial is another good 
> example where it greatly limits/impacts how one might model something... 
> I ran into it way back at point, circle, polygon (oops! non-fixed size). 
> I don't expect this can be feasibly made illegal in future... I expect 
> the warning/admoinishment to be softened, maybe with some good advice 
> about when such cardinality is warranted and when another pattern may be 
> a better choice.
> 
> my 2c,
> 
> 
> --
> Patrick Dowler
> Canadian Astronomy Data Centre
> Victoria, BC, Canada
> 
> 
> On Mon, 9 Mar 2020 at 06:05, Gerard Lemson <glemson1 at jhu.edu 
> <mailto:glemson1 at jhu.edu>> wrote:
> 
>     HI Mark____
> 
>     Just for now:____
> 
>      From the vo-dml spec:____
> 
>     “Modelers SHOULD NOT use open ended multiplicities, i.e. with
>     maxOccurs=-1, but it is not illegal in the current version of this
>     specification. "____
> 
>     indicates it is not illegal to use non-fixed size data type
>     instances. (not that I like them as you know)____
> 
>     __ __
> 
>     The fact that you think you need it here may be due to an
>     incompleteness in the model as I described in my previous email.____
> 
>     It may well be that the structure of the mapping, including
>     explicitly representation of what-is-mapped-to-what, could make the
>     need for an explicit indication of forward vs inverse redundant.____
> 
>     So looking forward to seeing more details of the model (and I can
>     comment on another thread).____
> 
>     __ __
> 
>     Cheers____
> 
>     Gerard____
> 
>     __ __
> 
>     __ __
> 
>     There are flavors which have open ended list of content____
> 
>         Lookup table has open ended list of Entries____
> 
>         Polynomials have open ended list of Coefficients,  to avoid
>     individually modeling the different order of polynomial functions.____
> 
>     __ __
> 
>     DataTypes are supposed to have fixed size.____
> 
>     __ __
> 
>     Mark____
> 

-- 
---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
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