[auscope-geosciml] CGI_Term/value should be nillable?

Sen, Marcus A. mase at bgs.ac.uk
Fri Jun 24 06:46:28 EDT 2011


> -----Original Message-----
> From: auscope-geosciml-bounces at lists.arcs.org.au [mailto:auscope-
> geosciml-bounces at lists.arcs.org.au] On Behalf Of Laxton, John L.
> Sent: 24 June 2011 11:02

> I don't see how value can be nillable as that is the principal
> information CGI_Term is delivering
The reason I was asking is that in our current BGS example instance we have...

<gsml:bodyMorphology>
	<cgu:CGI_Term>
		<cgu:qualifier
			xlink:href="http://resource.geosciml.org/classifier/cgi/ValueQualifier/200811/always" xlink:title="Always"
			xsi:nil="true"/>
		<cgu:value xlink:href="http://www.opengis.net/def/nil/OGC/0/unknown" xlink:title="Unknown"/>
	</cgu:CGI_Term>
</gsml:bodyMorphology>

This is using an OGC nil HTTP-URI in the xlink:href attribute but we have decided (https://www.seegrid.csiro.au/wiki/AppSchemas/NilValues) that we should use xsi:nil="true" with a nilReason attribute for nil properties. So, at first I was thinking of altering cgu:value above to something like

<cgu:value xsi:nil="true" nilReason="unknown" />

but cgu:value isn't nillable.

On reflection, the better thing to do in this case would be to nil the whole gsml:bodyMorphology property

<gsml:bodyMorphology xsi:nil="true" nilReason="unknown" />

as the meaning of a qualifier on an unknown value seems unclear, so maybe I don't want cgu:value to be nillable after all.

(In this example all our features have the same constant "unknown" bodyMorphology so it is easy to do. I'm not so sure how easy it will be to configure our WFS software where we have known values for some features but unknown for others and want to switch to using the xsi:nil pattern in the latter cases; I need to look into this.)

Marcus

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