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Re: Alternatives to containers/collections (was Re: Requirements for a possible "RDF 2.0")

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 14 Jan 2010 14:19:00 -0600
Cc: Danny Ayers <danny.ayers@gmail.com>, Steve Harris <steve.harris@garlik.com>, Semantic Web <semantic-web@w3.org>
Message-Id: <DC227E64-5EAB-47E0-B2A7-D2CB30A1B2E1@ihmc.us>
To: Dan Brickley <danbri@danbri.org>

On Jan 14, 2010, at 11:31 AM, Dan Brickley wrote:

> On Thu, Jan 14, 2010 at 4:20 PM, Pat Hayes <phayes@ihmc.us> wrote:
>> A lot, perhaps all, of this hair could be avoided if RDF allowed  
>> general
>> tuples as well as triples. All that is needed is some way to put N  
>> things
>> into a sequence: so, put N things into a sequence. The 'graph  
>> model' would
>> be a hyperlink, drawn as a polygon (eg triangle for N=3) rather  
>> than a line.
>> In triples-style syntax, it would just be moving a dot.
>
> I periodically wonder what an RDF without the binary restriction would
> look like.

My 2c suggestions, as answers to the questions.
>
> Would each property/relation have a fixed arity, eg. dc:source might
> 'be a 4', 'foaf:knows' a 7?

No. But it might be useful to distinguish 'really binary' ones, which  
only fit in triples, from the others, which can take any number of  
things in the sequence. Or maybe not, whatever. But the default should  
be, any number (even though most of them will be 2 in practice, ie  
triples.)

> That doesn't make a lot of sense to me. So
> presumably they'd vary freely. In which case, we have a lot of
> figuring out to do when wondering whether   livesWith(alice, bob,
> 2007, 'y') implies livesWith(alice,bob) or livesWith(alice, bob, 'y',
> 'foo.html'). The binary straightjacket makes some of these questions
> impossible, albeit maddeningly...

The Common Logic answer is very puritan: each number of arguments is a  
separate assertion, and they are all independent (unless you write  
axioms connecting them.) So liveswith(a b c) has nothing to do with  
liveswith(a b) or with liveswith(a b c d), etc., as far as the logic  
itself is concerned.  This is actually quite elegant and works well  
WHEN you can write the axioms you might need. So maybe we would need,  
for RDF, some way to attach some common inference patterns to these by  
giving properties to the property of the tuple. For example, one  
useful and common pattern allows ends of argument lists to be lopped  
off, so that

liveswith(alice, bob, <address>, <maritalstatus>)
entails
liveswith(alice, bob)

and we might specify this pattern (in a semantically extended RDF) by  
asserting

liveswith rdf:type rdf:ExtendableProperty .

But this is very much off the top of my head. Whaddayathink?

Pat


>
> Dan
>

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Received on Thursday, 14 January 2010 20:20:06 UTC

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