Jody Garnett wrote:
>> Another  example is the use of property types. Are these even  
>> present in the ISO
>> model, or are they a GML encoding artifact?
> 
> They are present in the ISO model.

I am not so sure. The GF_PropertyType in ISO 19109 is an abstract 
supertype of GF_AttributeType. I think this means that, if GeoAPI 
represents the ISO Feature Model, a Feature with complex properties 
should have them as immediate properties, not enclosed in wrapper 
complex properties like gml:FeaturePropertyType.

>> They appear to me to be present only to cause the striping rule to  
>> be observed.
>>
>> Some UML (see properties, and no property types):
>> https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicUnit
>> https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicFeature
> 
> Can you be more specific - I am not sure what I am looking at in these  
> UML models.

In the UML for GeologicUnit, you can see that a GeologicUnit has 0..* 
CompositionPart. Apologies for my ASCII UML:

GeologicUnit <>--- 1..* CompositionPart

In GML (the GeoSciML application schema), a GeologicUnitType has 0..* 
CompositionPartPropertyType properties, each of which contains a 
CompositionPartType:
http://www.geosciml.org/geosciml/2.0/xsd/geologicUnit.xsd

In UML, the XML looks like:

GeologicUnit <>--- 1..* CompositionPartProperty <>--- 1 CompositionPart

and the encoded XML has XPaths like this:

gsml:GeologicUnit/gsml:composition/gsml:CompositionPart

It seems to me that in GML an enclosing type has been introduced as an 
artifact to ensure that every complex property contains an element that 
gives its type information. To me this seems to be an encoding artifact 
that should be created at encoding time, not stored in our GeoAPI 
representation of the data. GML is only a representation of the GeoAPI 
model.

In short, should GeoAPI represent the General Feature Model or the GML 
encoding? Or am I missing something?

Kind regards,

-- 
Ben Caradoc-Davies <[email protected]>
Software Engineer, CSIRO Exploration and Mining
Australian Resources Research Centre
26 Dick Perry Ave, Kensington WA 6151, Australia

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