[Requests] Comments on WCS 2.0 draft

Dominic Lowe dominic.lowe at stfc.ac.uk
Tue Mar 30 12:44:59 EDT 2010




PART A


1. Evaluator:
         Dominic Lowe, STFC (OGC Member), dominic.lowe at stfc.ac.uk

2. Submission:
	09-110r2, WCS Core Interface Standard
	(These comments actually refers to schemas in the RFC bundle).



PART B


1. Comment: 1

2. Implementation Specification Section number: wcsGrids.xsd

3. Criticality:  Major

4. Comments/justifications for changes:

Description of AbstractReferenceableGrid in wcsGrids.xsd does
not match the description of AbstractReferenceableGrid in approved GML
CR 07-112r3.

wcsGrids.xsd states:
"This element and its type are copied from approved Change Request
07-112r3, which adds them to GML 3.2.1"

However the description of this element and type differs between
wcsGrids.xsd and 07-112r3

Specifically the final '<documentation>' sentence in wcsGrids.xsd
definition of AbstractReferenceableGrid refers to an internal crs:
"The inherited attribute group gml:SRSReferenceGroup shall link the
referenceable grid to the internal coordinate reference system of the
grid."

compared with 07-112r3 which refers to an external crs:
"The inherited attribute group gml:SRSReferenceGroup shall link the
referenceable grid to the external coordinate reference system to which
it is referenceable."

Furthermore it is noted that the only substantive amendment of accepted
CR 07-112r3 compared with the previous revision (07-112r2) was to
clarify that the SRSReferenceGroup shall link the referenceable grid to
the external coordinate reference system.

This comment recommends that the GML approved definition from 07-112r3 
is used for correct harmonization with GML.





1. Comment: 2

2. Implementation Specification Section number: wcsGrids.xsd

3. Criticality:  Major

4. Comments/justifications for changes:

The GML SWG recently voted against accepting change request
09-091 (Add ReferencedGridByTransformation :
https://portal.opengeospatial.org/files/?artifact_id=35116)

There is an assumption in wcsGrids.xsd that this change request would
have been approved by the GML SWG.
Specifically the documentation for element
"ReferencedGridByTransformation" states that "This element and its type
are copied from Change Request 09-091r1, which adds them to GML 3.2.1."

Given the aim of harmonisation between WCS and GML any
reliance in WCS 2.0 on 09-091 creates an potential barrier to GML
harmonisation. Specifically 09-091 reverses the decision of the GML SWG
that gml:SRSReferenceGroup shall link to the 'external' crs of the grid
- so this issue is also directly related to the above item.

This comment recommends that ReferencedGridByTransformation is not 
included in its current form in the WCS 2.0 specification for the same 
reasons it was not accepted as a GML CR and for the fact that it may 
therefore be a barrier to harmonisation with GML.





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