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Re: Media types and assertions

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 12 Mar 2004 09:42:50 -0600
Message-Id: <p06001f0dbc77885b4575@[10.0.100.76]>
To: Mark Baker <distobj@acm.org>
Cc: www-rdf-comments@w3.org

>On Thu, Mar 11, 2004 at 09:43:08PM -0600, Pat Hayes wrote:
>>  >As it would be if it were transferred with text/plain or
>>  >application/octet-stream.
>>
>>  Not at all. Unless you know it is RDF, you don't even have a chance
>>  of getting at the content. Conveying it as text/plain doesn't even
>>  tell you how to parse the logical form.
>
>Ah, I see.  By "content" I thought you meant the bytes.

Ah, no, sorry, I was speaking like a logician. I meant the logical 
content, the propositions expressed by the message.

>
>>  >The Web is concerned with more than content, it's concerned with being
>>  >able to serialize up meaning at one end of the pipe, and have it
>>  >accurately reconstituted at the other end.  The media type tells us what
>>  >spec to use to extract meaning from the document encapsulated in a Web
>>  >message, and so is arguably the most important piece of metadata used in
>>  >this process.
>>
>>  Ok, no argument with that. That's why one needs an RDF media type, to
>>  inform the engines that this is RDF rather than plain XML or plain
>>  text.
>
>Right.
>
>>   But all that is basically about what syntax level to parse it
>>  at, so one can get at the semantics. Asserted or not asserted, it is
>>  still RDF rather than plain text.
>
>Agreed.
>
>So in those terms, I claim that whether or not an RDF document is
>asserted is something the publisher of that document needs to make
>clear via the messages they send.

But why do you claim this? That isnt part of the logical syntax, and 
it seems to belong at a  layer above the propositional content. There 
are many things about the process of publishing things on the Web 
that are not made explicit in software-readable forms. RDF and OWL 
enable a new level of expression - the representation of 
machine-processable propositional content - that has not been 
available before.  You want something else as well; but you don't say 
WHY you want it, or what it is for. Seems to me that the best way to 
proceed is to let a larger community gain some realistic-scale 
experience with this new stuff, to see what the world really needs 
next. Maybe web speech acts will be one of the first things that will 
be needed. But right now nobody actually using this stuff (except you 
:-) seems to care about it strongly enough to think that they can't 
make progress without it.

>  The RDF specs don't help you with
>that, therefore, IMO, the media type registration(s) should.

Well, eventually I am sure that something will do it. I reserve 
judgement about whether media types are the best way to handle it, 
though. I think it will require something more complicated and 
nuanced. It almost certainly will have to be involved with trust and 
policy reasoning, for example.

>
>But my requirement (for my needs, at work) is simply that the
>"assertedness" of a document be indicated somewhere in the message.

Can you say why you need this? Suppose you go with the flow and just 
assume that any deployed RDF you find is being asserted. What will go 
wrong? Even if your software believes things like the test cases you 
are unlikely to get into serious trouble if you can legally parse the 
RDF, since they all use fake namespaces so will not interact with 
anything else.

Pat Hayes
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Received on Friday, 12 March 2004 10:42:54 UTC

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