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xsd:date in DCAT

From: Phil Archer <phila@w3.org>
Date: Thu, 04 Apr 2013 10:16:49 +0100
Message-ID: <515D4501.5000507@w3.org>
To: GLD Public Comments <public-gld-comments@w3.org>
Having noted this afternoon's agenda item on ADMS I'm working on that 
document right now which is causing me to look at DCAT more carefully 
than I have of late - which is my excuse for just noticing something I 
should have seen before. I ask that the WG treats this as a last call 

In the text related to the use of dcterms:issued [1] we say:

"rdfs:Literal typed as xsd:date. The date is encoded as a literal in 
"YYYY-MM-DD" form (ISO 8601 Date and Time Formats). If the specific day 
or month are not known, then 01 should be specified."

I remember raising this at our previous f2f last year as I find it 
objectionable that we actively encourage sloppy practice and inaccurate 

If I know that something was issued in March 2013 then I can write

dcterms:issued "2013-03"^^xsd:gYearMonth

That conveys exactly what I mean - that the thing was issued at some 
point between 2013-03-01T00:00:00 and 2013-03-31T23:59:59. But I don't 
know when. It is accurate, if not precise.

But DCAT says we shouldn't do this. We should render it as 2013-03-01 
which means that the thing was issued sometime in the 24 hour period 
known as 1st March. That may be wrong by as much as 30 days and gives an 
entirely bogus impression of accuracy.

I suspect that the reason for this is that catalogues habitually don't 
understand xsd:gYearMonth. If that's the case then that's 
application-specific and a profile may wish to make it clear that dates 
must be xsd:date only, even if that means it will create inaccuracies 
where none exist in the original data, but IMHO this sloppiness should 
not be included in the DCAT spec. Therefore I suggest that the text for 
this property says:

"rdfs:Literal using the relevant ISO 8601 Date and Time compliant string 
and typed using the appropriate XML Schema datatype [[XMLSCHEMA-2]]"

[1] http://www.w3.org/TR/vocab-dcat/#Property:catalog_release_date


Phil Archer
W3C eGovernment

+44 (0)7887 767755
Received on Thursday, 4 April 2013 09:17:22 UTC

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