[GeoSciML] 4.x potential change request

Boisvert2, Eric (NRCan/RNCan) eric.boisvert2 at canada.ca
Tue Sep 25 08:35:00 EDT 2018


Just emerging from summer gap / September madness

Following discussion with Teemu Lindqvist (GTK) -  I realised that we forgot to provide extension points to some of the GeologicStructure sub types.

As a reminder, we have AbstractDescription types (eg: EarthMaterialAbstractDescription. GeologicUnitAbstractDescription) to add more properties to existing types (here GeologicUnit) without subtyping the main feature type itself.  We all agree it's a hack to deal with UML/XSD, but I can't think of a better solution.  (In the mean time, I realised this is quite similar to "Strategy Design Pattern" in the Gang of 4 book).

Teemu started looking carefully at the model to assess usefulness for engineering geology, and pointed out there are no such *AbstractDescription for some of the GeologicStructure subtypes (Fracture, Lineation, Layering).  So for those, the only way to add properties is to subtype them.

In retrospect, this most probably happened because the initial motivation to create AbstractDescription classes was to move the properties into Extension, and Fraction, Lineration, Layering were moved completely into Extension  - so, no need to pull the properties from them.  And Fracture/Join does not even have properties at all (other than the one inherited).

So this means that one can add new properties to gsmlb:Folitation by extending FoliationAbstractDescription but must subtype Layering to do the same.
I think we just forgot the *AsbtractDescription pattern could be used outside our immediate need to split Basic/Extension.

Adding AbstractDescription to those subclasses would be a backward compatible change to 4.1 (or add a single generic AbstractDescription to GeologicStructure which will be inherited by all sub classes).

The other - clunky -  but without any change option to the model is to use GeologicFeatureRelation and pack you new property in a GeologicFeature (ugh - this makes me think of cars with snow plows)


Thoughts ?

Eric Boisvert
Expert  TI-GI / IT-IM Expert
eric.boisvert2 at canada.ca<mailto:eric.boisvert2 at canada.ca>,
orcid: http://orcid.org/0000-0001-6256-2912
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