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Re: Social meaning discussion 6th March

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 4 Mar 2003 12:18:17 -0500
Message-Id: <p05111b06ba8a8cf71a13@[64.134.139.17]>
To: Graham Klyne <GK@NineByNine.org>
Cc: Tim Berners-Lee <timbl@w3.org>, Dan Brickley <danbri@w3.org>, Brian McBride <bwm@hplb.hpl.hp.com>, pat hayes <phayes@ai.uwf.edu>, Bijan Parsia <bparsia@isis.unc.edu>, RDF Core <w3c-rdfcore-wg@w3.org>

>At 10:31 PM 3/1/03 -0700, pat hayes wrote:
>>>  Something has one meaning.
>>
>>This isn't true even in ordinary human discourse in natural 
>>language. There just is no such notion of a single 'one meaning'; 
>>the idea isn't coherent.
>
>Pat,
>
>I'd like to explore this a little, noting that RDF is not "ordinary 
>human discourse in natural language".
>
>Stepping back from meaning that can be formally specified, I'd like 
>to try a notion of a single meaning (in RDF):
>(a) each URI used has exactly one denotation
>(b) each URI used as a property has just one relational extension
>
>(A consequence --for which this is sufficient but not necessary-- 
>would be that the truth or falsity of any expression using a given 
>vocabulary of URIs is fixed.)
>
>I'm not attempting to describe a specific interpretation in the 
>model theoretic sense.

Well, in fact you are. That is, if you fix the denotations and the 
relational extensions, you've fixed everything.

>Though I suspect that there can be only one such interpretation (on 
>a given vocabulary) that could concur with such a meaning.

Right.

>
>We have no way of fully specifying such a "one meaning", but I think 
>it's reasonable to allow that we can develop successive 
>approximations that converge (asymptotically, as it were) to such a 
>meaning.

Well, maybe that is a reasonable idea, but there are several 
limitations to it, since one can easily show that there is never a 
single such satisfying interpretation as far as the MT is concerned. 
So the single intended model has to be defined by some extra-MT-ish 
constraints.

More seriously in the context of the original thread, this entire 
picture assumes that it makes sense to think in MT terms over a range 
of languages. This is indeed possible with RDF/S/OWL-Full, but (a) 
setting this up was a major piece of work, and amounted to making 
these into a single language; it is meaningless when we are supposed 
to have a single meaning which crosses arbitrary language boundaries; 
and (b) it may well not be possible for future languages, or 
extensions which take the RDF/S/OWL axis in some other direction (eg 
some of the 'rules' proposals).

Pat

>
>This may not be a useful idea, but I'm trying here to see if there 
>may be ways to reconcile what I think are two apparently-reasonable 
>viewpoints.
>
>#g
>--
>
>At 10:31 PM 3/1/03 -0700, pat hayes wrote:
>>>Jeremy Carroll wrote:
>>>
>>>>
>>>>tbl:
>>>>
>>>>>>>2. The meaning of the statement is defined by the definition
>>>>>>>of the predicate, as applying to the subject and object 
>>>>>>>identified by the
>>>>>>>definition of the subject and object terms.
>>>>
>>>>Danbri:
>>>>
>>>>>>This for me is the crux: do we mean the machine oriented 'definition'
>>>>>>in RDFS or OWL or N3, or some more rounded/scruffy/social 
>>>>>>notion of definition.
>>>>
>>>>
>>>>I find Bijan's observation compelling
>>>>[[
>>>>But there's no vague, much less precise, definition of "defining 
>>>>information". And I'm a logical reasoner, will this information 
>>>>be opaque to me? (Well, if in German, yes, but *all* human 
>>>>reasoners?)
>>>>[...]
>>>>So it's formal meaning isn't fixed IN ANY WAY by the "authority"? 
>>>>And the social meaning?
>>>>]]
>>>
>>>
>>>There seem to be a confusion here that things have two meanings, a 
>>>"formal" one
>>>and a "social" one.    I don't think that is useful.
>>
>>I think it is essential, although this way of putting it is 
>>potentially confusing. It might be better to distinguish between 
>>how much of the meaning is accessible to who and to what. The 
>>'formal' meaning is that part which is accessible to software. But 
>>even the 'social' part, ie all the rest, varies from reader to 
>>reader. In some cases, a reader might find more meaning than the 
>>original writer thought was in the document.
>>
>>>  Something has one meaning.
>>
>>This isn't true even in ordinary human discourse in natural 
>>language. There just is no such notion of a single 'one meaning'; 
>>the idea isn't coherent.
>>
>>>"inverseProperty" can be defined mathemaically, but remember that  the
>>>mathematical symbols used are probably defined in english somewhere.
>>
>>That is highly debateable and depends what you mean by 'defined', 
>>but in any case its irrelevant to the issue here. If your point is 
>>that *all* meanings are ultimately described in English, that isn't 
>>true.
>>
>>>"color" can't be defined formally in terms of mathemaics, unless you have
>>>assume a lot of other terms to do with spectral reflectivity and light.
>>
>>Well, "color" actually can be defined in scientific terms, in fact, 
>>but you'd be better with an example like "red" which probably can't 
>>be defined at all. This has got nothing whatever to do with 
>>mathematics, but it does tend to show that there isn't any single 
>>meaning to words like color names.
>>
>>>>
>>>>Two points:
>>>>- "whatevers available" is simply not clear enough.
>>>
>>>There are a lot of social systems for relating definitoins to terms.
>>>These include domain name owndership, the Web, etc.
>>>The web is a big place.  Predciates and terms vary enormously.
>>>For RDF to be able to describe real things, it is essential that
>>>some terms be defined in english.
>>
>>Why English? And why is this true? You can't define "red" in 
>>English. And more to the point, maybe, what does 'defined' mean 
>>here? RDF can't use definitions given in English.
>>
>>>  Look at the cyc ontology.
>>
>>That is a very bad example for your point: the intended purpose of 
>>Cyc is precisely NOT to rely on English definitions.  The meaning 
>>of any CYC term is completely defined by the CYC axioms using that 
>>term (and all linked axioms, ie ultimately by the whole of Cyc.) 
>>You can strip out all the English comments and the meaning is 
>>unchanged. The same goes for almost all large-scale ontology work, 
>>in fact.
>>
>>>I'm not sure what you are unhappy with, here.
>>>Are you saying it is not clear enough?
>>
>>It certainly is not clear enough.
>>
>>>Are you saying that
>>>it is not clear what the definitions of the terms are?
>>
>>It is clear that any English definitions cannot be reflected in any 
>>normative account of meaning which is reflected in any operation of 
>>any RDF software. IF RDF tries to incorporate any such notion of 
>>meaning into its spec, then it has just become a joke.
>>
>>>Are you saying that the english definitions should not be allowed?
>>
>>Allowed in what sense? What I am saying is that allowed or not, 
>>they are not the slightest actual USE. Any sense of 'meaning' which 
>>depends on them isn't going to influence in any way what any piece 
>>of software does to the RDF. And since the point of the spec is 
>>largely to help writers of software, referring to something that is 
>>necessarily irrelevant is either pointless or actively harmful.
>>
>>>Or do you want a clean algorithm for determining which
>>>english documents define a given term, from the web?  (That we 
>>>could probably
>>>arrange.)
>>
>>That would be very interesting. I doubt if this can even be made 
>>precise enough to be meaningful, let alone provided as an 
>>algorithm. And in any case, suppose you could. Now, how is my RDF 
>>engine going to read and understand those English documents?
>>
>>>>
>>>>- RDF has decided to avoid the notion of definition for the 
>>>>formal semantics, we shouldn't then have it in the informal 
>>>>semantics.
>>>
>>>Well, every specification upon  which the web has depended up till 
>>>now, including
>>>Ethernet and unicode and TCP/IP and HTTP has had the meaning of its terms
>>>and structures explained in english, informally.  These specs have been used
>>>to build software, resolve many discussions,  and so on.
>>
>>Yes, but this reply misses an essential point. The part of those 
>>specs whose meaning is fixed between software apps is the part that 
>>can be specified in the specs. None of those specs have set out to 
>>define a general meaning-carrying representation. In the case of 
>>ontology languages like RDF, the common part that can be defined by 
>>the spec is the *general rules* for meanings, ie the semantics, NOT 
>>the 'meaning' of particular RDF URIrefs. The spec says nothing at 
>>all about what <ex:myUri> 'means', and if you write a document in 
>>English explaining what its supposed to mean, then its not the 
>>slightest use or relevance, since no piece of software on the 
>>planet in the forseeable future is going to be able to read your 
>>English 'definition'.
>>
>>>  There are a mass of
>>>RDF schemas and related documents going to be written -- but it 
>>>needs the RDF
>>>spec to pass on the authority to them to define their fields.
>>
>>I don't see how the spec of a language can, or should, pass on any 
>>authority to define anything. It didnt have the authority to define 
>>the meanings of any items not in its namespace in the first place. 
>>What it can do, and does, it specify how to characterize the 
>>content of any piece of the language, so that definers of meanings 
>>can determine how to constrain those meanings using the language. 
>>That is what the model theory sets out to do.
>>
>>>Just because *some* aspects of the meaning of *some* RDF terms can
>>>be expressed formally
>>
>>THOSE ARE THE ONLY ASPECTS OF MEANING DEFINED BY THE SPEC. If you 
>>want the spec to define other aspects of meaning, please tell us 
>>how to write it (the spec) so as to refer to those other aspects of 
>>meaning. Its not good just using words like "meaning" and 
>>"definition" without saying what we mean by them. Words like this 
>>don't have exact enough meanings to use in a specification.
>>
>>>   does not remove the duty of the RDF spec to
>>>say what an RDF document means.
>>
>>The SPEC cannot possibly say what a particular RDF document means, 
>>any more than a dictionary can tell a story. It can only give 
>>general rules for attaching meanings to documents, which is what 
>>the semantics does.
>>
>>>The formal semantics cannot define "color".
>>
>>Right, and "color" can't be defined in RDF.
>>
>>>Suppose I send you an RDF document syaing (in n3)
>>>
>>><http://example.info/ips/gg5#y004> <http://example.com/dsaf#enFap> "176".
>>>
>>>How would you know what I was telling you?
>>
>>I would know that some thing had some property with value '176' (a 
>>string), and if that's all the RDF I can see, that is ALL I know. 
>>If you want me to know more, you had better send me some more RDF.
>>
>>>How would someone who had not heard of RDF before?
>>>The mime type would take them to the RDF spec and -- then what?
>>
>>The above is what I would learn from the RDF spec. Of course the 
>>RDF spec can't tell me what you mean by 
>><http://example.info/ips/gg5#y004>; and you might tell ME what you 
>>mean in English, but (this being the semantic web) that's largely 
>>irrelevant; the question at issue is what some piece of software 
>>acting on my behalf can get out of it. If its written in English, 
>>the answer is, nothing.
>>
>>>>For me, either of these is fatal. This cat has had its nine lives.
>>>
>>>Fatal for the idea of defining what an RDF document means?
>>>How sad.
>>>In that case, I suppose we had better start all over again, as
>>>we have ended up with a languge of meaningless documents.
>>
>>You can start over all you want, but you will not get anything much 
>>better than this (except in the sense that OWL is better than RDF, 
>>and full FOL would be better than OWL). To get better than this you 
>>will need to create a web of movie-style Artifical Intelligences, 
>>and you won't get that done by a W3C working group. All languages - 
>>even human languages like English - are 'meaningless' in some very 
>>strict sense. Their meaning is what a cognitive agent can get out 
>>of them, and RDF agents - in fact, any software agents that we know 
>>how to build -  have pretty limited cognitive powers.
>>
>>>If  RDF is only be to be used to encode mathmeatical
>>>formalisms,  and not information about the real world,
>>>do we need another langauge to express data?
>>
>>This discussion has nothing to do with mathematics versus the real 
>>world. Model theory is about worlds, including the real world. The 
>>point at issue is HOW MUCH INFORMATION is encoded in some RDF; and 
>>the answer is, rather little. But we knew that up front, before we 
>>started. It is obvious that RDF cannot encode the kind of 
>>information that humans can send to one another using languages 
>>like English, in a form useable by software agents. But that's not 
>>a failure of RDF: *nothing* can do this. To do this would require 
>>us to be able to provide software with human-level cognitive powers.
>>
>>Pat Hayes
>>--
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>
>-------------------
>Graham Klyne
><GK@NineByNine.org>
>PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E


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Received on Tuesday, 4 March 2003 12:18:58 EST

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