[crm-sig] Question about temporal validity

martin martin at ics.forth.gr
Fri Jun 17 14:36:34 EEST 2005


Dear Patrick,

You send me a message about how to model for instance a serial
changing from Monthly to Quarterly.

The CRM has no mechanism for temporal validity of properties. That was
outcome of early decisions, because no relevant data structures at museums could be found that
did such things. Equally the CRM does not model any kind of growth
or continuous change. Further temporal validity implies knowledge about
states, whereas we prefer registering state transition event for reasons of
monotonicity.

The partial mechanism to deal with that is the Transformation event, where
a new unit or sub-unit is defined, which may or may not have the properties
of the previous one. This is well justified as long as the properties that change are
"essential", but may cause proliferation of subunits in case of
non-essential properties, and causes replication of all unchanged properties.

For the purpose of information integration, it is normally sufficient
to sum up all properties within a phase, even if they did not co-occur.
So the serial would simply be "Monthly" and "Quarterly", not stating when
in particular. Details may go into a note. This would not cause much noise
in a respective query.

The only system I am aware of that dealt comprehensively with temporal validity
is the full version of TELOS, implemented at some sites. Each property and classification is associated
with a valid-time stamp, and a belief-time stamp. The implementation
became so heavy that to my knowledge there was no particular uptake of this
technique, but I do not know what OWL or other current languages or systems
do support.

So, an extension of the CRM using properties of properties could do the job,
a kind of "reification".

Comments welcome.

Best,

martin
-- 

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  Dr. Martin Doerr              |  Vox:+30(2810)391625        |
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