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Re: Tech Plenary: agenda Best Practices

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 5 Mar 2004 19:25:54 -0600
Message-Id: <p06001f19bc6e5ad301aa@[]>
To: Christopher Welty <welty@us.ibm.com>
Cc: public-swbp-wg@w3.org

Hi Chris

>I don't deny being a philosophical pundit and I enjoy preaching it 
>from on high, and I will continue to do so.  

Boldly said.

>Of course people are free to ignore it.

Of course. And they are also free to disagree with it, and to tell 
the world that it is best ignored. You have been warned :-).

>  The SW best practices working group is not to be confused with the 
>SW required practices working group, which in some sense is what 
>webont was (webont produced a standard, swbp will not).
>BTW, Most of my philosophical ideas concerning ontology have been 
>tested in the real world and that's where I get the primary 
>justification and motivation to preach it from on high.  

Then I'd suggest (1)  stick to the tested parts and (2)  avoid making 
implicit claims to intellectual authority by using grand-sounding 
language referring to philosophical, as opposed to practical, sources.

>When programming languages  were first introduced, the world of 
>programming was left open as you seem to propose here for OWL, and 
>it created a mess.

What mess was that, exactly?  People are still writing code in 
Fortran and LISP and C, but most of the languages designed by 
preachers have faded into history.

>  THere have always been people preaching good programming practices 
>and there have always been people who ignored it.

There has also been no shortage of people preaching, designing and 
even mandating extremely poor programing practices.  And it has been 
notoriously hard to even tell which was which until after the event.

>  There is nothing about preaching from on high that precludes 
>listening or learning (as a teacher I always learned as much from my 
>students as they did from me), nor do the particular things I preach 
>claim to be solutions to everything.
>So, again, I consider it part of our mandate to define some "best" 
>practises, not just any practises.  For me, these will be based 
>primarily on my real experiences building actual systems that use 
>ontologies, and influenced by my somewhat selective knowledge of 
>I can respond to your points about mereology, modal logic, etc. 
>later, those are more specific comments.
>PS I thoroughly enjoy messages that mix comments like " let the 
>advice be severely pragmatic and free from philosophical punditry." 
>and "the first two of these both have their intellectual roots in 
>the same strand of Polish philosophy from the late 1800s in Warsaw, 
>for some reason."  I suggest you embrace your own philosophical 
>punditry, join the brotherhood, and preach it from high, low, middle 
>- wherever.  I'm expecting to have you as a co-conspirator because I 
>know you can't help yourself either.

You are conflating knowledge with punditry. I enjoy formal philosophy 
but I don't take it to be in any way authoritative, and I enjoy 
noticing historical links like this because they give a sense of 
perspective. (BTW, that reference was slightly muddled. Brentano was 
German/Austrian: the Polish reference was to Lesniewski.)


The problem with mereology (and things like it) as a guide to 
practice is that, like most philosophically motivated theories, it 
tries to be a universal theory of everything. Varzi's excellent 
article http://plato.stanford.edu/entries/mereology/  makes this 
quite clear: it is a theory of parthood IN GENERAL, and is supposed 
to cover every possible sense of 'part', including things like 
physical parts, parts of space and time, pieces of text, parts of 
abstracta, parts of the human soul (one of Brentano's primary 
concerns), parthood in static settings, in dynamic settings, in 
Platonic worlds, etc. . The practical trouble with this motivation is 
twofold.  First, there isn't very much you can reliably say about 
things at this level of generality. It is too easy to find intuitive 
objections to almost any axiom from some source or other (which is 
why general mereology is so weak as a formal system, and even at its 
strongest only gets to be similar to a theory of subsets, rather than 
a theory of set membership.) Second, whatever you do come up with 
isn't much real use anyway, since any particular application of a 
theory of parthood will be about one sense in particular, and most of 
the utility comes from the characteristics of this particular sense 
of 'part', the ones that distinguish it from other senses. This last 
is a very general point, which I learnt from Doug Lenat: the very 
high levels of an ontology are of little importance in practice. Its 
the middle levels where the axioms do the real work. Philosophers 
rarely descend to these middle levels; the concepts are too dense and 
complicated for them to handle. (There is also another reason, which 
works in the other direction: philosophers will often modify or 
reject an idea for philosophical (often described as 'principled' or 
'foundational') reasons, when in fact, in practice, it is quite OK to 
use it. The general philosophical-foundational desire to keep the 
conceptual universe parsimonious is a frequent cause of this.  Cyc 
has axioms in it about arbitrary combinations of stuffs being a stuff 
that would leave many philosophers shaking their heads about all 
those crazy stuff-kind individuals. The Cyc attitude is pragmatic and 
works fine in practice: if you don't think those things exist, don't 
use the axiom. See also Jerry Hobbs' writings on 'ontological 
promiscuity' for more on this theme.)

Now, don't get me wrong, I don't mean to imply that everything called 
'mereology' is useless. If one is interested in axiomatizing a real 
notion of part in, say, a machinery catalog, then it is probably 
worth knowing about some of the applied mereology work. It also has 
applications in ontologies for geographical space, for example, 
because geographical space is indeed very mereological-ish: it can be 
carved up arbitrarily, combined arbitrarily, and is kind of defined 
by its extent. But these applied theories aren't useful because they 
are mereologies (and 'parthood' is some kind of magic key to the 
universe): they are useful because they fit their intended domain 
quite well.  Take mereology and geographical space, for example.  A 
colleague and I once developed a basic ontology for geographical 
space which turned out, after a lot of work, to be almost exactly 
like Tarski's 1935 axiomatization of 'general extensional mereology'. 
I could have saved some time by just knowing more about Tarski, 
except that what I found out was a genuinely *geographical* 
motivation for those axioms: you can derive the 'unique fusion axiom' 
(P12' in Varzi's article) from the requirement that map projections 
are invertible, which is needed in order to make sense of the idea of 
a map having a well-defined semantics. So I don't see this as a 
mereological axiom at all: in this application, it is essentially a 
*cartographical* axiom. In this application, all that stuff about 
parthood being fundamental to the universe is baloney: the intuitions 
come from the idea of rendering a map on a surface as a description 
of geographical space. And this kind of insight is genuinely useful, 
because it ties the formal ontology to intuitions that are robust in 
the application domain, instead of to very abstract, evanescent ideas 
that one quickly loses confidence in, so cease to be useful guides to 
what axioms to write. (Similar comments apply to the notion of a 
'boundary' in geography, as opposed to in philosophical generality. 
You want to find out about geographic boundaries, ask a surveyor or a 
civil servant or a soldier or a map-maker: don't read Aristotle.)

A good guide needs to tell users that they should not assume that 
their problem has been solved by virtue of some Great Thinker having 
made a Universal theory, and they can just take the solution off the 
shelf and run with it. They need to think it through, to see if it 
applies where they need it to apply, or if it needs to be modified. 
They need to think about whether their notion of parthood is really 
transitive or not., and maybe be given some guidance on how to find 
out. They need to think about issues like, what it means to replace a 
part (does the whole with the replaced part stay the same thing or 
does it change? Or both, in two senses that we probably need to 
distinguish? Or is this just not an issue?) They need to be warned 
about the places where an apparently obvious axiom (if the parts are 
all the same, the whole is the same; a part of a part is a part) 
might turn around and bite them (a disassembled lathe isn't a lathe; 
a ballbearing might be part of a bearing assembly but not part of an 
engine.)  Being told that the guys who publish in the journals that 
*real* philosophers read are of the opinion that parthood is 
necessarily transitive and non-diachronic is kind of beside the point.



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Received on Friday, 5 March 2004 20:26:00 EST

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