Dear All,
Here my proposal for a text about temporal validity of properties for
the CRM introduction:
Properties, such as having a part, an owner or a location, may change
many times for a single item during its existence. Stating instances of
such properties for an item in terms of the CRM only means that these
properties existed at some time-span. Therefore, one item may have
multiple instances of the same property reflecting an aggregation of
these instances over its time-span of existence. If more temporal
details are required, the CRM recommends to explicitly describe the
events of acquiring or loosing such property instances explicitly, such
as E9 Move etc. By virtue of these principle, the CRM achieves
monotonicity with respect to an increase of knowledge about the states
of an item at different times regardless of their temporal order.
However, for some of these properties many collection databases describe
the "current" state, such as "current location" or "current owner".
Using such a "current" state means, that the database maintainer is able
to verify the respective reality at the latest date of validity of the
database. Obviously, this information is non-monotonic, i.e., it
requires deletion when the state changes. In order to preserve a reduced
monotonicity, these properties have time-neutral superproperties by
which respective instances can be reclassified if the validity becomes
unknown or no more holds. Therefore the use of such properties in the
CRM is only recommended if they can be maintained consistently.
Otherwise, they should be reclassified by their time-neutral
superproperties. This hold in particular if data are exported to another
repository.
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Dr. Martin Doerr | Vox:+30(2810)391625 |
Research Director | Fax:+30(2810)391638 |
| Email: [email protected] |
|
Center for Cultural Informatics |
Information Systems Laboratory |
Institute of Computer Science |
Foundation for Research and Technology - Hellas (FORTH) |
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Web-site: http://www.ics.forth.gr/isl |
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