[Crm-sig] Extended CRM Graph of E52 Time-Span

martin martin at ics.forth.gr
Thu Jul 2 20:01:55 EEST 2009


Bernhard Schiemann wrote:
> Dear SIG,
> Find attached the Erlangen CRM variant of the graphical representation
> of CRM's E52. Maybe we can discuss the yellow areas in the graph as
> extensions or additions to the CRM?
> 
> 
> kind regards
> Ben
> 
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Dear Bernhard,

Obviously, the xsd:dateTime does not have the properties by which the TimePrimitive
in the CRM is characterized, namely to represent an Interval. The recommended implementation
is not, to attach to E61 a primitive value, such as xsd:dateTime, but to replace E61 by
the primitive values a certain implementation foresees:

"This class comprises instances of E59 Primitive Value for time that should be implemented with appropriate validation, precision and 
interval logic to express date ranges relevant to cultural documentation. "

This indirection does not serve anything. Once you have no interval primitive,
you better declare P81a, P81b, P82a, P82b, from E52 Time-Span to xsd:dateTime,
describing the endpoints of the outer and inner interval, as Christian-Emil points out,
and delete E61 from the OWL schema.

The idea to extend P79, P80 is not very helpful: These links describe reasons or qualifiers
of datings. The Time-Span is, as Christian-Emil points out, determined by four values, and not
two, which would logically conflict with P81,P82.

Note, that any implementation representing a Primitive Value in a suitable form is part of an
information system, and thereby not of an ontology in the proper sense. Therefore, an extension
as I describe above, i.e., P81a, P81b, P82a, P82b, from E52 Time-Span to xsd:dateTime, is a compatible
interpretation of the CIDOC Model, it does what the ontology intends to describe for your OWL environment.
As such, it cannot be a CRM extension, but is a compatible implementation.

This is yet another example why a database schema is not an ontology...

The links P79a, P80a you are proposing are ultimately incompatible, because they introduce ambiguity of meaning between
P79a,P80a and P81 and P82.

Similarly, any implementation of the CIDOC Model should make suitable replacements of ALL Primitive Value classes
according to the local abilities.

Best,

Martin


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