On 10/29/2011 12:58 PM, Paul Brown via Cory Casanave:
> It occurs to me that there are two distinct notions of type that are
> relevant here: representational type (as defined in a schema), and
> ontological type, reflecting what can happen in the real world. To me, a
> representational type defines the aspects that are relevant (whether
> mandatory or optional) in the context for which the representation was
> designed. If the representational types are mapped to the ontological
> types that they represent, then these mappings can be used to relate
> representational types via the ontological types. This is Cory’s pivot. (01)
I agree that the distinction is important. But I would say that the
representational types (and the schemata that define them) are a version
of ontology. (02)
To give an example, consider the ontology of Amazon.com, which would
represent real-world items that they sell, the customers who buy them,
and the suppliers that provide them. For each of those things, their
software would only use a small subset of the information about them. (03)
They would also require an ontology about time, space, and events
to cover the locations of their customers and suppliers, the taxes
for those locations, the shipping methods and times, the kinds of
events that might cause delays (holidays, weather), etc. (04)
But Amazon would also have an ontology of their business, the
software that supports it, and the kinds of operations for
all the interactions with customers, suppliers, locations. (05)
What Paul calls the representational type consists of the union of
the business ontology, the software ontology, and a very small subset
of the ontologies for all the real-world people, places, things,
and events that the business must deal with. (06)
This observation does not automatically solve the problem, but it shows
how the problem can be restated: (07)
1. Information federation is a problem of relating multiple ontologies. (08)
2. Some ontologies may have a very large overlap, such as the ontology
of Amazon's business with Amazon's software. (09)
3. But other ontologies may have a small overlap with the information
that Amazon needs. For example, a customer may be defined as a
human being, but only a tiny subset of all the possible information
is relevant to the operation of their software -- name, address,
credit card, previous purchases, etc. (010)
4. Using the same tools to format the information may simplify the
syntactic problems, but it does not solve the semantic issues.
Matching a supplier's RDB to Amazon's RDB is a nontrivial task. (011)
Sometimes, there are mismatches along the way. This morning I received
email from Amazon with a notice of a big bargain: (012)
> Maxell Rewritable DVD+RW (15-Pack)
> by Maxell
>
> List Price: $366.99
> Price: $10.57
> You Save: $356.42 (97%) (013)
A discount of 97% sounds very good, but there was undoubtedly some
mistake with the list price. (014)
By the way, anybody who is looking for realistic use cases for
information federation and ontology merging should look at the
Amazon specifications. They are publicly available, and the task
of matching a supplier's software to the Amazon schema takes a
considerable amount of time and effort. (015)
John (016)
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