Dear All,
Here my trial guideline:
Frequently scholars and scientists would like to express more detail
about a particular relation (property) between two entities than the
type of the property itself expresses. These may be more details about
the respective role or attitudes or arguments about the reliability of
the information. In order to formally attach notes to properties in the
currently dominant knowledge representation languages, one needs to
replace the property by an equivalent path with an intermediate,
auxiliary entity. Even though this mechanism has been provided for the
CRM as "property classes", it considerably increases the complexity of
the model and the user interface and decreases the performance of
respective databases. The details given are in most cases not relevant
in order to filter a large set of data by it. In that case they are
relevant for the receiving user, but not for querying, and hence can be
better expressed in a textual note.
The question that arises, is where to put the note, if not to an
intermediate entity: to the domain instance or the range instance of the
respective property. This is often intuitively done in the opposite way
it should be done.
For instance: "Building house X"(E12) - P4 was carried out by - "John
Smith"(E21)- P3 has note: "in the role of designer" sound perfectly
logical, but is wrong!
This is the effect of context-free propositions in KR. The user sees the
local context, but the note is attached to the person, not to the
building activity. The role however does not hold for the person at all
times, but only for this person in this activity. If "John Smith" will
have another role in another activity, the context of this role becomes
ambiguous. Therefore, if a note is meant to describe a property, but is
instead attached to either domain or range instance, it must contain, in
textual form, the path to the other entity instance.
This leaves two choices for the above example:
A)
"Building house X"(E12) - P4 was carried out by - "John Smith"(E21).
"Building house X"(E12) - P3 has note: "was carried out by John Smith in
the role of designer"
B)
"Building house X"(E12) - P4 was carried out by - "John Smith"(E21) P3
has note: "performed Building house X in the role of designer"
Since the instance "Building house X"(E12) is actually the *context* for
this role, or, in other terms, more specific to the property instance
than the actor, the rule is to attach a note about a property to the
more specific domain or range instance, as shown in choice A) in the
above example, if the property is not going to be expanded by an
intermediate entity. Then one has to repeat the missing path in the note
as shown above.
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Dr. Martin Doerr
Honorary Head of the
Center for Cultural Informatics
Information Systems Laboratory
Institute of Computer Science
Foundation for Research and Technology - Hellas (FORTH)
N.Plastira 100, Vassilika Vouton,
GR70013 Heraklion,Crete,Greece
Vox:+30(2810)391625
Email:[email protected]
Web-site:http://www.ics.forth.gr/isl
