On Oct 14, 2008, at 1:23 PM, Sean Barker wrote:
Paola
The
question was about what are the expectations of the terms in an
ontology. The Semantic Web version seems to suggest that you just pick
up on the terms that you are interested in, and that's enough.
However, if the term is just the start of a chain of inference, then
someone reading only the term will mis-understand the term, at least to
some extent. In principle, to understand the term in the way that it is
meant, one should follow the inferences which the sender has made, and
probably with the same inference engine - hence the need for
omniscience.
Let me clarify the idea of the semantic web, as this is exasperatingly
close but misses the crucial insight. First, its not necessary have the same
inference engine; only an engine which conforms to the published specs, all
of which have been carefully and consciously written so as to NOT commit to
a particular engine, but instead only to a common semantics. Any engine
which draws valid inferences according to the published semantics is
acceptable.
SB> Agreed, but I had been advised that in practice different
engines may give different results, particularly if one is forward-chaining,
the other backward chaining. Is there any process of certifying an inference
engine actually performs as specified?
Second, its not necessary
to have all the inference chains in order to understand the content. That is
the whole point of inference: you can do it for yourself, with confidence.
If I send you some SWeb content and you draw valid conclusions from it, then
those conclusions are just as much part of what I have sent you as if I had
sent them directly. You have a blanket licence, provided by the published
specifications of the notations themselves, to draw such conclusions. That
is WHY I don't need to send them all to you, you see.
SB> If the primary source publishes all the the information it
infers from, yes. However, the primary source may have made inferences
from other secondary sources, and I have not noted in any of the standards
any obligation on a source to identify the sources it has also used. Does
this therefore oblige the user to search for other sources on the web? And
how would the user know what secondary sources had been used by the primary
source? It is the assumption that the sources are also active consumers of
information rather than passive providers that raises the question of
omniscience.
You state in your reply to Len "When you publish some SWeb content, you
take on the
responsibility for supplying enough information to enable a
reader to
draw the appropriate conclusions. If some assumptions are
left
'implicit', then you, the publisher, have not done your job
properly."
What is the mechanism for this when you have made inferences from
secondary sources?
Copying all the other sources to your content page is
surely
the opposite of the way the web works. Conversely, a
mechanism to redirect a user
to the other sources would suffer from configuration
problems, as the other urces will mostly
likely change over
time.
Alternatively, one might hypothesise that individuals
may only pick up on the knowledge they need - use only the terms without
further inference. That means that they have, to some extent,
misunderstood the
term.
No. They can do as much inference or as little as they like. But their
not doing so does not imply that they are MISunderstanding anything. They
may need only a very limited set of valid conclusions to do their job. That
is not misunderstanding.
SB> Not quite. If correct understanding requires some
level of inference, and the user fails to make this inference, then
they have misunderstood. If they only need a partial understanding,
then agreed it would not be appropriate to call it misunderstanding
with respect to their purpose, however, it may still remain a
misunderstanding with respect to the source's purpose (an occurrence
which many love stories rely on).
This raises two questions; firstly, how can one quantify the
level of misunderstanding? and secondly, how can one then determine if
the level of misunderstanding is significant?
Behind this is my
suspicion is that many people start with the assumtion that, say, nouns
name things or concepts. An alternative is that nouns are a grammatical
category that allow people to play particular word games. Many
- but not all - of these games are games that relate to named
things or concepts. One problem for ontology development is to exclude
from an ontology the nouns which do not name things (are games
only) - all though they may have a function in meta-ontology
conversations. For example, I would classify "property" as defining one
such game. We can cite as properties of a ball its shape, colour, age or
cost without suggesting that there is anything in common between shape,
colour age or cost (other than being a property). Conversely, the game
property rules out "being owned by" or "having followed a particular
course" as properties.
Not in the game played in ontology writing, I assure you. Those are
just as much properties of the ball as its color is. One of the basic rules
of this game is to refrain from drawing 'lines in the sand' like this, as
they don't help get anything done and often get in the way.
SB> The observation was about the habitual use of
English, rather than the technical redrawing of the rules for ontology
games. If I were to state "It is a property of this ball that it has
followed the path from my foot through that window" this would
have the pragmatic of claiming that the broken window was not my
fault, and the statement would be classified as false. The fact
that it may be true for an ontology writer is confirmation
that "property" defines a game. The point is not that it is invalid to
play such games, but rather, that it is invalid to infer that a
word that is used to play a particular game necessarily refers to
something in the world which is not a game.
Pat Hayes
Further, I suspect most
terms in an upper ontology to be word games, that is,
that these terms are contexts in which a particular set of
metaphysical rules may be applied, where:
Context - an agreement on the things
germane to a conversation
Metaphysical rule - a criterion for
distinguishing categories within a context - e.g. change is germane to
physical objects but not to abstract things like numbers.
(At least Ambrose Bierce might
agree).
Sean Barker
Bristol, UK
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Sean
I am curious what is the preamble for this,
or are you just following your train of thoughts?
I have been
working on some aspects of distributed knowledge, in particular in
relation to my interest in 'expertfinding ', and I am interested
in what you say but of all things , its your conclusion that strikes a
chord with me
One
might also observe that to base everything on a single,
comprehensive
ontology, one would need to be
omniscient.
Not necessarily. A single unified ontology can be a
model for omniscience, but individuals (people and machines) only
access parts of it at any given time, until and unless , our cognitive
apparatus (the way we learn and make inferences) is radically
overhauled.
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