Re: How to model valid time of resource properties?

Hi Kingsley,


> On October 15, 2014 at 2:59 PM Kingsley Idehen <kidehen@openlinksw.com> wrote:
> 
>  On 10/15/14 8:36 AM, Frans Knibbe | Geodan wrote:
> 
>      > >      On 2014-10-13 14:14, John Walker wrote:
> > 
> >          > > > 
> > >          Hi Frans,
> > > 
> > >          See this example:
> > >          http://patterns.dataincubator.org/book/qualified-relation.html
> > > 
> > >      > >      Thank you John! Strangely enough, I had not come across the
> > >      > > Linked Data Patterns book before. But I can see it is a valuable
> > >      > > resource with solutions for many common problems. And it looks
> > >      > > pretty too! I am sure it will come in handy for problems that I
> > >      > > haven't stumbled upon yet.
> > 
> >      A nice thing about this solution is that it doesn't need any extensions
> > of core technologies. I do see some downsides, though:
> > 
> >      Let's assume I want to publish data about people, as in the examples. A
> > person can have common properties defined by the FOAF vocabulary, like
> > foaf:age or foaf:based_near. Properties like these are likely to change. If
> > I want to record the time in which a statement is valid I would have to
> > create a class for that relationship and add properties to that class that
> > will allow me to associate a start time and an end time with the class. But
> > by doing that I would not only be forced to create my own vocabulary, I
> > would also replace common web wide semantics with my own semantics. Or would
> > it still be possible to relate the original property with the custom class
> > somehow?
> > 
> >      In the cases known to me that require the recording of history of
> > resources, all resource properties (except for the identifier) are things
> > that can change in time. If this pattern would be applied, it would have to
> > be applied to all properties, leading to vocabularies exploding and becoming
> > unwieldy, as described in the Discussion paragraph.
> > 
> >      I think that the desire to annotate statements with things like valid
> > time is very common. Wouldn't it be funny if the best solution to a such a
> > common and relatively straightforward requirement is to create large custom
> > vocabularies?
> > 
> >      Regards,
> >      Frans
> > 
> >  >  Frans,
> 
>  How about reified RDF statements?
> 
>  I think discounting RDF reification vocabulary is yet another act of
> premature optimization, in regards to the Semantic Web meme :)
> 

Just wondering if the semantics of RDF reification would accurately capture the
semantics of what Frans wants to model.

If the idea is to capture the start and end date of a relationship, then is RDF
reification the answer in this case?

As the reified statement has rdf:type rdf:Statement, wouldn't we that be making
the additional statements about the statement, not about the relationship it
represents. If so, what does it mean to indicate a start and end date of a
statement?

To use a real life example discussed during Pilod [3] we have multiple
conflicting source of information:

Tax office records show Alice and Bob were married from 2010-03-01 to
2014-01-01.
Local council records show Alice and Bob were married from 2001-03-01 to
2014-10-10.

This probably requires a mix of different modelling techniques and there's no
right or wrong way to do it.

[3] http://www.pilod.nl/

>  Some examples:
> 
>  [1] http://bit.ly/utterances-since-sept-11-2014 -- List of statements made
> from a point in time.
>  [2] http://linkeddata.uriburner.com/c/8EPG33 -- About Connotation
> 
These are great examples of using RDF reification, good stuff!
It's really clear that here you are capturing additonal (meta)data about who
made the statement, when, etc.

John

> 
>  --
>  Regards,
> 
>  Kingsley Idehen
>  Founder & CEO
>  OpenLink Software
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