|From:||William Frank <williamf.frank@xxxxxxxxx>|
|Date:||Thu, 8 Mar 2012 12:23:15 -0500|
I think is the essence of this point is:|
"The number of possible conflicts is infinite, and no fixed set
of universal definitions can anticipate and rule out all of them."
This is true of *logical necessity*; so it is something that we always live with
The reason for this truth is that
there is no guarantee that all the models for
any theory G are consistent with one another. Two applications
A and B that are each consistent with G can have info in their
local contexts that conflict with info in the other's context.
More strongly, unless the theory G is complete, which no theory as expressed in an application will be (only theories as bounded and richly expressed as second order arithmetic tend to be complete),
there will always be models, describe in theories G' that are extensions of G, as expressed in different applications, that ARE inconsistent with each other. As in John's example, "an employee must be at least 21 years of age," may be a rule expressed in one applicaton, while in another employees may be 16, or have no specified age limits.
But, unless I am mistaken,ontologies should express ONLY what is true about concepts by their very meaning, what is "true by definition,"* such as that employees work for some institution or person, and are bound by some agreement with them, with respect to that work, rather than expressing things that are not an essential part of the concept of employee, but only a policy stipulated at a given institution, such as how old employees must be. Then, ontologies cannot and should not provide whatever "full interoperability" might be, as opposed to the economic ecosystem collaboration that for example S.W.I.F.T has enabled, seemingly without running up against these kinds of problems. ( Historical evidence that what Paul says and we all seem to agree with is true: "My only claim is that if you use URIs consistently for referring to things, and RDF consistently for making assertions about things, you have an easy road to improved communication.)
*This ignore the embarassing fact that the line between what is true by defintion and what is true by current prescription is not sharp, but that is a different topic, and the above still holds: "this is an employee of C, so therefore he has some kind of agreement with the employing institution about their relationship." is sound reasoning, (if no such agreement exists, then he is not an employee, whether believed to be or not) but only a particular well known kind of foolish reasoning would say, "well this is an employee, so therefore he MUST be at least 21." Maybe he used a false id? The only thing we can reason is, this is an employee of C, so therefore, if C's HR did their job properly, they have sufficient reason to believe he is at least 21.
On Thu, Mar 8, 2012 at 11:16 AM, John F. Sowa <sowa@xxxxxxxxxxx> wrote:
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