Hi all,
This is a early "heads-up" on some outputs of a data modelling workshop
I recently participated in that provided an opportunity to explore some
of the relationships between "Simple" and "General" Features and
Coverages, and the underlying phenomena being modelled.
A communique is being prepared with the position reached, but I see
there is various discussion and effort being expended in areas of
relavnce now, and I wanted to put forward some of the ideas to see if
they prompted any discussion.
1) A coverage is a Feature describing the state ("range") of a spatially
distributed phenomenon In many (if not all!) is in fact some sort of
special case of an Observation Feature where the procedure is a remote
sensor, a chain of models or a sampling regime.
2) a WPS may act on Feature Types
So the (usually contentious!) statetment #1 becomes a "no-brainer" when
seen in the context of #2
This also allows us to coherently model a domain irrespective of whether
we collect or package the data as features or coverages.
Other corollaries include:
* A WCS is really a convenience API for the general WFS, where the
FeatureTypes served are coverages
* A WFS can equally serve a coverage feature
* A coverage feature can link the range to a streaming protocol to serve
values - e.g. JPIP
A more profound outcome is that FeatureTypes are polymorphic - and the
"representation views" of a "conceptual model" can be described in terms
of the "operations" that can be done - Simon Cox has dubbed these
"processing affordances". This is not that profound in some ways, since
ISO19110 clearly states this, but in practice we have lacked mechanisms,
and most domain models have been driven by inconsistent approaches -
geometry-centric, semantic, processing-oriented aspects governing the
typology. We can now resolve all these we beleive in a single
methodology, that allows you to have typical "shapefile"
representational views without crippling the underlying conceptual model
of the domain (for example losing all the metadata for an observation).
If this leaves you cold, fine, you probably have minimal actual
interoperability requirements, but hopefully this will allow a few of
you to find some coherence in a range of activities which are being
inexorably drawn together, and prime you to read and respond to the
forthcoming findings.
Cheers
Rob Atkinson
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