How to model valid time of resource properties?

Hello!

I wonder if a way of recording changes in properties of resources can be 
recommended. Many resources in real life have properties that have a 
time range of being valid. In some datasets, only the current (or most 
recent) state of a resource is stored, but in many cases it is important 
to keep track of the history of development of a resource.

An example:

:john_smith
     a foaf:person ;
     foaf:name "John Smith" ;

Let's say that on 2013-09-27 John Smith marries Betty Jones. John Smith 
is still the same person, so it makes sense to extend the same resource, 
not create a new version:

:john_smith
     a foaf:person ;
     foaf:name "John Smith" ;
     ex:marriedTo :betty_jones ;

How could I efficiently express the fact that the statement :john_smith 
ex:marriedTo :betty_jones is valid from 2013-09-27? And if the couple 
divorces, that the property has expired after a certain date? It would 
be nice if the way of modelling makes it easy to request the most recent 
state of a resource, any historical state, or a list of changes during a 
time period.

A quick web scan on the subject revealed some interesting research 
papers, but as far as I can tell all solutions need extensions of RDF 
and/or SPARQL to work.

Perhaps this question is really about the ability to make statements 
about a triple? Which is a problem for which no satisfactory solution 
has been found yet?

Regards,

Frans

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Frans Knibbe
Geodan
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1079 MB Amsterdam (NL)

T +31 (0)20 - 5711 347
E frans.knibbe@geodan.nl
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