Then we can add a third class, call it “System” and put that
name in a NameType intentionally constructed by Matthew. The point was that the
name doesn’t matter as long as we can identify the extent of the class. For
example, I might decide to call the class you identified “widget”.
Extensionally, it’s the same class, I just give it a different name. Because
IDEAS/BORO has a sophisticated(ish) naming pattern, I know that when Canadians
say “system” they are referring to a different class to the one you call
“system”.
We didn’t have the option to impose a new definition of “system”
on any of the parties.
[MW] That’s fine. My approach is usually to try to find the most
general sense, and then qualify it to produce the more restricted senses. This
has the advantage of giving you a model that shows the relationships between
them.
They had their own definitions, and a tiny ontology project was
going to stop the combined systems engineering departments of some the largest
defence agencies in the world from doing things their own way. The same goes
inside companies, I should add. This is why corporate taxonomies are all
given a stiff ignoring by the users, and one of the reasons why all those
“corporate data model” projects of the 1990s ended up producing something
no-one ever used. Either the users don’t agree with the terminology (in which
case, they dismiss it off hand), or they see a word they think they recognise
and use the model/taxonomy in an unexpected manner.
[MW] Which is why with the DDM we (including you) tried hard to
preserve the meaning the business gave to terms, but place them in the ontology
such that they were correctly defined by the relationships they had to other
entity types (especially subtype/supertype).
Regards
Matthew West
Information Junction
Tel: +44 560 302 3685
Mobile: +44 750 3385279
matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
http://www.matthew-west.org.uk/
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in England and Wales No. 6632177.
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<snip>
The big challenge in ontology is to figure out what’s different
about a system to any other physical item.
[MW] I agree
Why is a car considered a system, but a rock isn’t, for example.
We had a lot of debates around this in IDEAS meetings. You can easily
ascertain the extents of aircraft, armoured vehicles, etc., but the extent of
the classes each nation were calling system differed. The UK framework (MODAF)
saw a system as any kind of man-made object that had functionality (i.e.
cars=yes, rocks and humans = no). The Canadians were very specific that a
physical object only became a system when it was manned, maintained and ready
to function – a narrower set than the UK one. The US (DoDAF) description was
similar to the UK but also included humans/animals. So, we had three
overlapping classes, each of which was called “system” by different parties. By
extensional analysis, we worked out that what MODAF calls
“CapabilityConfiguration” was an exact match for the Canadian “System”.
[MW] Well I don’t think any of those are wrong, but perhaps a
little restrictive. The two things that characterise a system for me are:
1.
It has a function/capability/purpose.
2.
Has parts that can be
replaced by functionally equivalent parts.
Regards
Matthew
West
Information Junction
Tel: +44 560 302 3685
Mobile: +44 750 3385279
matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
http://www.matthew-west.org.uk/
This email originates from Information Junction Ltd. Registered
in England and Wales No. 6632177.
Registered office: 2 Brookside, Meadow Way, Letchworth Garden
City, Hertfordshire, SG6 3JE.