Rich and Gary, (01)
Rich's note on the new thread of Quality is related to Gary's
comment about quality in this thread. So I'll discuss them
both in this thread. (02)
RC
> I found this quote on a SEMWEB list:
>
> “(_X) tells me that empirical evidence suggests that using a
> larger number of relationships correlates to poorer ontologies.”
>
> Note that _X reportedly used the descriptive word “relationship”,
> not the usual suspect “relation”, so the total number of
> tuples/rows/records in each relation that involves the ontology,
> summed over all such relations, would seem to capture the intuitive
> meaning of that phrase. (03)
The word 'relationship' usually refers to instances rather than types.
For example, a person with a thousand Facebook "friends" has a thousand
relationships of the same type. (04)
I suspect that _X was counting instances rather than types. Perhaps
_X meant that a better ontology might choose relation types that
could represent the same information with fewer instances. (05)
For example, the verb 'buy' could be defined by two instances of 'give': (06)
X buys Y from Z for W amount of money: (07)
X gives W to Z in order to cause Z to give W to X. (08)
If your ontology does not have the concept type Buy, it would have
more instances of the simpler relations. Perhaps that is _X's
measure of quality. But you might ask _X. (09)
GBC
> John’s example was the cutting up of some water domain into various
> categories (rivers, steams etc.) that often come to have a term
> associated with it. We might have an application dealing with floods
> in which these distinctions are important. To start on a quality
> ontology for such an application it should be able to make meaningful
> statements about what exists in its focused domain. (010)
I agree that if a term is significant for a particular domain a good
ontology should provide some way to express it. Sometimes, the formal
definitions have a very direct mapping to the informal terms, but
sometimes a different choice of formal relations might be more useful. (011)
For the example about floods, you might represent the basic idea
of water flowing in a channel at a certain rate (say cubic meters
per second). The common terms, such as creek, stream, and river
might be less useful, since a flooded creek might have a greater
flow than a river during a dry spell. (012)
You might also choose to represent the maximum desired channel
depth and define a flood by the distance above that depth. (013)
GBC
> The hydrological concepts are more basic and underlie the real world
> phenomena at the river-stream level. For many applications they will
> therefore organized things. (014)
That depends on your application. If you happen to be a landscape
designer, you might consider the common terms as useful ways to
characterize the visual features in your design. (015)
GBC
> ... for IT applications we need to formalize these axioms in a language
> that on the one hand faithfully reflects this conceptualization and
> on the other can be processed by applications. (016)
Yes, but I would emphasize the word 'application'. The quality of
an ontology depends critically on the way its used in an application.
Even for the same basic phenomena, different ontologies might be better
suited to one purpose or another. (017)
John (018)
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