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Re: New proposal (Re: getting rid of xsd:dateTime ?)

From: Felix Sasaki <felix.sasaki@fh-potsdam.de>
Date: Wed, 6 Apr 2011 09:35:13 +0200
Message-ID: <BANLkTi=pe13xqEmzQdMYmb_ekbFALi1QKw@mail.gmail.com>
To: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
Cc: "public-media-annotation@w3.org" <public-media-annotation@w3.org>
Hi Pierre-Antoine,

2011/4/6 Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>

> Felix,
>
> On 04/06/2011 12:32 AM, Felix Sasaki wrote:
> > 2011/4/5 Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr
> > <mailto:pierre-antoine.champin@liris.cnrs.fr>>
> >
> >     Hi all,
> >
> >     there seem to be a recurring problem with dates and the ma: ontology.
> I
> >     encountered it, Martin encountered it, I know that Joakim also did...
> >
> >     The fact is that most metadata formats we are dealing with allow
> dates
> >     to be more or less precise, like
> >
> >     * just a year
> >
> > in XML Schema, this would be gYear
> http://www.w3.org/TR/xmlschema-2/#gYear
> >
> >     * a year and a month
> >
> > this would be http://www.w3.org/TR/xmlschema-2/#gYearMonth
> >
> >     * a year, a month and a day
> >
> > this would be date http://www.w3.org/TR/xmlschema-2/#date
>
>
> You are completely right.
>
>
> >     * ...
> >
> >     while xsd:dateTime imposes to us to commit to a 1sec precision...
> >
> >     I suggest we change the range of date properties to rdfs:Literal, and
> >     specify in the documentation that they should be of the form
> >     YYYY[-MM[-DD[Thh[:mm[:ss[.fff]]]]]], to be interpreted as an
> incomplete
> >     date.
> >
> > This would be very bad. RDF in many areas is linked to XML datatypes,
> > see e.g. http://www.w3.org/TR/rdf-primer/#typedliterals , and I would
> > encourage us to follow this approach as close as possible. To solve your
> > problems, I would rather say that a date should be one of the above
> > built in XML Schema data types.
>
> I probably jumped to fast to the proposal above, for the reasons
> explained below. Nevertheless I agree with you that a better solution
> would be that section 4.5 be rewritten:
>
>  A Date value MUST be represented using one of the following XML
>  Schema datatypes: gYear, gYearMonth, date, dateTime, dateTimeStamp,
>  depending on the precision available on the data.
>
> NB: I add dateTimeStamp which is new in XSD 1.1 [1], and imposes a
> timezone. I know that XSD 1.1. is not recommended yet, but OWL2 found a
> nice way to get around this problem [2].
>
> This would have to be reflected in the API document as well [3].
>
>
> Now, if I had to do only pure RDF, I would be happy with this solution.
> My problem is that we have been asked in some comments to make the
> ontology compliant with the OWL2-RL profile which, I think, makes sense
> (OWL-RL inferences can be efficiently implemented on top of a rule
> language). And OWL2-RL does not support xsd:gYear or xsd:gYearMonth. In
> fact, on only support dateTime and dateTimeStamp [4].
>
> Hence my first proposal to use the smallest common denominator
> (rdfs:Literal), although we lose some semantics in the process.
>
>
> Here is a second proposal that I think will suit you better: we leave
> the range of 'date' (and its subproperties) *unspecified* in the OWL
> ontology, and refer to the document to explain that only date-related
> datatypes are expected (and only dateTime[Stamp] are supported by OWL2-RL).
>


This sounds good to me, so also a +1 like Florian in this thread. I think it
might be worthwhile to explain the issue in our spec, basically use your
text in this thread, so that users understand the rationale.

Out of curiosity: Do you know why OWL2-RL only supports the above date /
time related types?

Felix


>
> On the one hand, I'm afraid that this is only translating the problem
> from the ontology to the data: if people publish data using a datatype
> not supported by OWL2-QL, will their data be correctly processed by a
> OWL2-QL inference engine?...
>
> On the other hand, this would *allow* people to use the correct datatype
> if they want to, and/or to be compliant with OWL2-QL if they want to.
>
>  pa
>
> [1] http://www.w3.org/TR/xmlschema11-2/
> [2]
>
> http://www.w3.org/TR/2009/REC-owl2-conformance-20091027/#XML_Schema_Datatypes
> [3]
>
> http://dev.w3.org/2008/video/mediaann/mediaont-api-1.0/mediaont-api-1.0.html#attributes-7
> [4] http://www.w3.org/TR/owl2-profiles/#Entities_3
>
> >
> > Felix
> >
> >
> >
> >
> >     This hinders interoperability a tiny bit, but not as much as
> inventing a
> >     day and an hour for media resources for which we only know the year.
> >
> >      pa
> >
> >
> >
> >     To all, some general remarks and conclusions
> >
> >     * as most metadata format are more permissive regarding dates than
> >     xsd:dateTime, I suggest we simply use rdfs:Literal for all our date
> >     properties, and explain that it should be of the form
> >     YYYY[-MM[-DD[Thh[:mm[:ss[.fff]]]]]]
> >
> >
>
>
>
Received on Wednesday, 6 April 2011 07:35:41 UTC

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