RE: Temporal validity: alternative for dcterms:valid?

Hi Frans,

On Thursday, January 21, 2016 1:28 PM, Frans Knibbe wrote:

> I notice a friction between a standard for a temporal property (dcterms:valid in
> this case) and standards for expressing time on the other hand. A solution does
> not necessarily have to found at the side of the time data type. In this case, if
> dcterms were to change the range restriction the problem would be solved too.
> I can imagine that there are other vocabularies that assume time can always
> be captured in a single literal. Perhaps that needs to change?

But if we change the range from Literal to something else (e. g. time:TemporalThing), we also make it an object property instead of a datatype property and then we cannot use it with (date) strings. Or we could of course just remove the range restriction and use either a resource or a string in the object position but then we're in OWL Full and might hamper decidability (if that is a requirement).

Best,

Lars

> P.S. we know each other from the public-sdw-wg list, but this discussion is
> taking place on public-lod. I thought perhaps you hadn't spotted that.

Ah, no I hadn't spotted that so I cc the SDW list, too.

> 2016-01-13 21:43 GMT+01:00 <Simon.Cox@csiro.au>:
> OK - I understand.
> 
> However, I'm generally wary of inventing new microsyntaxes.
> We already have
> (i) time position - 7 information items in a string
> (ii) WKT
> 
> Back in the day I was responsible for developing DCMI:Period, DCMI:Box,
> DCMI:Point. I now regret those, since it was essentially just about field
> separators and punctuation. Since XML was emerging at the time it was all
> rather unnecessary.
> 
> Now we have RDF for structuring complex data, so best not create more syntax.
> (yes, I know the "/" interval separator is in ISO 8601, but didn't make it into
> XML, so there is no software to support it. )
> 
> Simon
> 
> -----Original Message-----
> From: Svensson, Lars [mailto:L.Svensson@dnb.de]
> Sent: Thursday, 14 January 2016 3:58 AM
> To: Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au>; frans.knibbe@geodan.nl
> Cc: public-lod@w3.org
> Subject: RE: Temporal validity: alternative for dcterms:valid?
> 
> On Tuesday, January 12, 2016 10:13 PM, Simon.Cox@csiro.au wrote:
> 
> > > an interval datatype similar to the ISO 8601 format ("2007-03-
> > 01T13:00:00Z/2008-05-11T15:30:00Z") -- where start and end could be
> > any xsd temporal datatype -- would be useful. Perhaps we can include
> > that in the time deliverable.
> >
> > time:Interval already exists in OWL-Time, which will be the basis for
> > the SDW time deliverable.
> > (In fact it is the fundamental class in the Allen calculus.)
> 
> Yes, but here the idea is to create a _datatype_ so that we can use a literal
> (essentially a microsyntax) as the object of dct:valid, e. g.
> 
> :someAssertion dct:valid "2015-12-31 / 2016-01-01T01:00:00Z"^^time:interval .
> # interval with a minor i, not the class Interval...
> 
> The temporal expressions before and after the '/' map nicely to
> time:hasBeginning and time:hasEnd and can thus be transformed to an instance
> of time:Interval (the class) and they can have different specificity (as in the
> example).
> 
> There is a similar proposal in EDTF [1] but there the syntax only allows year,
> year-month or year-month-day, and I think we should allow any of the
> date/time-datatypes in xsd.
> 
> [1] http://www.loc.gov/standards/datetime/pre-submission.html#interval

> 
> /Lars
> 
> > -----Original Message-----
> > From: Svensson, Lars [mailto:L.Svensson@dnb.de]
> > Sent: Wednesday, 13 January 2016 3:41 AM
> > To: Frans Knibbe <frans.knibbe@geodan.nl>
> > Cc: public-lod@w3.org
> > Subject: RE: Temporal validity: alternative for dcterms:valid?
> >
> > Frans, all,
> >
> > (Sorry for a latish reply, I'm still catching up on email...)
> >
> > On Thursday, December 24, 2015 4:57 PM, Frans Knibbe wrote:
> >
> > > The DCMI Metadata Terms vocabulary seems to have all the basic
> > > ingredients for building a versioning mechanism in to a dataset
> > > (which is or should be a very common requirement). Objects in a
> > > dataset can have life spans (temporal validity), be versions
> > > (dcterms:hasVersion/dcterms:isVersionOf) of another resource and
> > > replace
> > each other (dcterms:replaces/dcterms:isReplacedBy).
> > > But as Jeni Tennison has noted some time ago (see final section
> > > 'Unanswered Questions'), a versioning scheme based on DCMI has a
> > > weak
> > > spot: the property for denoting temporal validity (dcterms:valid) is
> > > impractical to the point of being unusable. Dcterms:valid only takes
> > > literals (rdfs:Literal) as value, which makes it hard to use it for
> > > practical expressions of time intervals. Time intervals should be
> > > compound objects that are based on useful datatypes. For instance,
> > > xsd:dateTime (for dates) or xsd:integer (for years or seconds (e.g.
> > > in UNIX
> > time)) could be used in SPARQL queries to filter or order temporal data.
> > > In a versioned dataset queries like 'give me all changes between
> > > time
> > > T1 and time T2' or 'give me the state of the dataset at time T3'
> > > should be easy to create and to resolve. It seems to me that this
> > > requires proper and well supported data types. A text string
> > > notation for time intervals is recommended by DCMI: dcmi-period. It
> > > is easy and versatile enough, but the average triple store probably
> > > does not recognize
> > this notation as temporal or numerical data.
> > > So I wonder if there is a good alternative for dcterms:valid
> > > somewhere that can be used to indicate temporal validity.
> >
> > I don't have a solution but only wanted to throw in that this question
> > was discussed on public-lod in November 2013 [1] and that no real
> > conclusion was found there either... That said, I still think an
> > interval datatype similar to the ISO 8601 format
> > ("2007-03-01T13:00:00Z/2008-05-11T15:30:00Z") -- where start and end
> > could be any xsd temporal datatype -- would be useful. Perhaps we can
> include that in the time deliverable.
> >
> > [1] starting at https://lists.w3.org/Archives/Public/public-

> > lod/2013Nov/0019.html
> >
> > Best,
> >
> > Lars

Received on Wednesday, 27 January 2016 09:05:39 UTC