From: Mike Bennett [mailto:mbennett@xxxxxxxxxxxxxxx]
To: [ontolog-forum] [mailto:ontolog-forum@xxxxxxxxxxxxxxxx]
Sent: Sat, 06 Sep 2008 12:21:44 -0500
Subject: Re: [ontolog-forum] Thing and Class
John,
The IBM component idea is pretty much universal nowadays in system
design, as the "Least Replaceable Assembly" or some such name. Designers
are encouraged to design such that these are replaceable in the field
with a minimum of spares holding, which leads to something like object
design for hardware, and of course standard backplanes.
As a result, something like a fire alarm system, HVAC system or
emergency shutdown system consists entirely and only of parts (like your
rifle). This is further complicated by the fact that the parts are often
arranged in a dual-redundant or triplicated arrangement. The result is
that the "Continuant Thing" which is your industrial system, continues
to exist and function when any one of these parts fails, rather like a
person with one kidney, except that it continues to perform according to
the full design specification (all it loses when a component fails, is
the ability to survive a further similar failure). So unlike the family
axe or the rifle it remains the same thing, without that part.
The same is true of many non-manufactured things, though. A tree grows from a sapling and then loses two limbs in a hurricane, all the time remaining the same tree. We all lose and gain cells by the hundred every minute, but remain the same person, with the same body; and so on. Some things are in a permanent state of dynamic replenishment, and wouldn't be possible any other way, yet we individuate them as one lasting thing: rivers, tsunami waves, thunderstorms, the Olympic flame, etc.. And I think the point of the family axe is that is really is the same axe, even though none of its parts are original. Continuity of the assembly need not depend on continuity of its components. We choose, for practical reasons, to individuate some pieces of the dynamic world as 'being the same thing' even though their physical make-up, either of components in an assembly or of actual physical stuff, may change. In some cases - a shadow (see Casati's wonderful monograph) or an edge - there need not be any actual physical 'parts' of the 'thing' at all, yet we will still individuate it and name it if we find it useful to do so. Shadows are real enough, but they are not part of anything and have no substance. Edges are real enough, and can even be dangerous, even though they have no volume and cannot be made of anything.
The moral is that this should not be surprising or challenging. Why should the individuation criteria across time be determined by parthood? The two topics have, prima facia, nothing really to do with one another. I think we expect that they should because in the (common) case where something is not thought of as having parts, when it is nothing more than a piece of stuff, we tend to use sameness of that stuff as the individuating criterion; but even here , the rule is not universal: a vase and pile of broken vase-pieces are not the same thing.
I must admit I struggled with the parts thing, having tried to create an
ontology framework based around your first/second/third order,
continuant v occurrent and concrete v abstract. I could not see that any
of these corresponded to "Part" so I wondered whether to add that to
this overall framework or if I was missing something.
In the end I went for defining "Part" as a continuant, relative thing,
with a relationship "is part of" to "Continuant Thing", with the inverse
relationship "has part" from Continuant Thing to Continuant Thing.
I suggest that to relate parthood to continuant is a mistake, in general. First of all, the very idea of a continuant is seriously flawed. Second, non-continuant things can surely have parts; and, most serious of all, the whole point of examples like these is that even if one believes in continuants, you will be forced to admit that there are continuants whose identity criteria are completely at odds with any account of how they are made up of parts or components. As Heraclitus noted some time ago, if a river is made of the water that comprises it, then you never step in the same river twice. But still, rivers are made of water: its the water that makes your foot wet, after all.
Pat Hayes
My
reasoning was that a thing can be a continuant thing and still be a part
of another thing, but a thing defined as a Part is a second order
definition of that (first order, continuant) thing as a part. I'm not
sure if the inverse property should be to Part instead.
I've no idea if that's the best way to do it but it seems to cover the
requirements. For example I have "Contractual Terms Set" as a part of a
Contract, and this is used when modelling relationships between say a
bond security and its interest payment terms, which are a kind of
Contractual Terms Set.
Mike
John F. Sowa wrote:
>This thread touches on many practical and philosophical issues, which
>have important implications.
>
>MB> An interesting ontological problem, otherwise known as the
> > "Family axe" i.e. this axe has been in our family for generations.
> > My father replaced the handle, his father replaced the head etc.
>
>The US Army had a problem with identifying rifles. They kept
>track of the rifle assigned to each soldier, but not of the parts,
>which could be replaced. But what if a soldier requested parts
>one at a time and reassembled them to form a duplicate rifle?
>
>Their solution was to declare that one part could not be replaced.
>That was the stock, which had a unique serial number. If the stock
>was broken, the soldier had to replace the entire rifle.
>
>SB> In engineering practice (at least as described through ISO
> > 10303), a part is either an inseparable component or an assembly.
> > An assembly consists of sub-assemblies (which are assemblies)
> > and components. The definition of assembly is recursive.
>
>Fifty years ago, almost all products were built as assemblies.
>Anybody who had modest skills with a screwdriver and a set of
>wrenches could take apart, reassemble, and repair cars, toasters,
>and even radios. But getting beyond replacing tubes in the radio
>required some technical knowledge and skill with a soldering iron.
>
>When individual transistors became integrated circuits, the
>"field replaceable units", as IBM called them, kept getting
>bigger and more expensive. For their Quasar TV sets, Motorola
>had the bright idea of designing components as pluggable units
>that could be replaced as easily as vacuum tubes. Unfortunately,
>the most unreliable components turned out to be the plugs.
>Furthermore, the cost of maintaining a vast inventory of such
>units was prohibitive. As a result, Quasar TVs were more
>expensive and more unreliable than competing brands.
>
>LO> The replacement and maintenance problem in the "equipment" area
> > is very like to the "replacement" and "maintenance" in the Personnel
> > area ! In the IFS ERP product they are under the common "object"
> > topic . Suppose it will be good to have some common description
> > for them although of course it will be hard to describe a body as
> > an "assembling" .
>
>For living organisms, there are no assemblies. Every component
>grows from a single egg that divides and subdivides into the
>specialized cells of every organ from skin to bones to lungs to
>the heart and brain. A heart may be replaceable, but a successful
>replacement requires adjacent cells to grow, subdivide, and bond
>together. As a result, the new heart becomes seamlessly integrated
>with the other organs of the body.
>
>RHM> Thus my concept hierarchy - my point of view - changes
> > with time, as the parts are assembled or disassembled.
>
>That is one more reason why a strict tree is an inadequate
>logical structure for representing an ontology. Aristotle's
>syllogisms supported multiple inheritance, and Leibniz took
>the next step of systematizing the partial order into a lattice.
>
>With a partial ordering (multiple inheritance) the type hierarchy
>need not change, even though individual instances may be changing
>constantly.
>
>DN> Alignment with UML at a conceptual level is probably a great
> > goal given it allows the structure to also be expressed in UML.
> > If UML is not robust enough, custom stereotypes can easily be
> > built into a UML profile.
>
>I strongly agree. My major complaint about the Semantic Web is
>that the designers ignored the most widely used official and
>de facto standards and practices in comp. sci. and IT.
>
>UML and relational DBs are two examples, but there are many others
>that they ignored. Now they complain that commercial enterprises
>ignore their recommendations. That shouldn't be a surprise.
>
>John Sowa
>
>
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--
Mike Bennett
Director
Hypercube Ltd.
89 Worship Street
London EC2A 2BF
Tel: 020 7917 9522
Mob: 07721 420 730
www.hypercube.co.uk
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