- From: Pat Hayes <phayes@ihmc.us>
- Date: Sat, 19 Mar 2011 20:29:31 -0500
- To: Sandro Hawke <sandro@w3.org>
- Cc: Andy Seaborne <andy.seaborne@epimorphics.com>, RDF Working Group <public-rdf-wg@w3.org>
On Mar 19, 2011, at 7:16 PM, Sandro Hawke wrote:
> On Sat, 2011-03-19 at 19:02 -0500, Pat Hayes wrote:
>> On Mar 18, 2011, at 3:56 PM, Sandro Hawke wrote:
>>
>>> On Fri, 2011-03-18 at 19:22 +0000, Andy Seaborne wrote:
>>>>
>>>> Is g-snap->g-text is just a function of the content type?
>>>
>>> Well, probably, for our purposes, I think so.
>>>
>>> There's a trivial case where it's not: the arbitrary non-semantic
>>> variability in serialization, eg whitespace. So, some notion of
>>> equivalence class of g-texts may be important.
>>
>> Can't we simply *define* g-texts to be equivalent under such trivial variations? It is our notion, after all.
>
> I'm not quite sure what you mean. I think it's important the g-text be
> a subclass of character or byte strings, so *equality* is string
> equality.
Well, that kills my suggestion right there. So let me push back on this point. Why do you think this is important? Why should a g-text not have its own g-style notion of equality? Why should it be a subclass of byte strings?
> For equivalence, yes, it seems like there's a simple and
> obvious meaning of equivalence, but I don't know how to formalize it,
You did later in the message :-)
I guess my overall question is, why do we need to distinguish identity from equivalence? Maybe this question is a residue from when I used to think like a mathematician, but I'd be interested in your answer.
Pat
> and I maybe it's not that quite that simple, for example:
>
> g-text t1: '_:x <http://www.w3.org/2000/01/rdf-schema#comment> "Hello"'
> g-text t2: '_:x <http://www.w3.org/2000/01/rdf-schema#comment> "Hello"'
> g-text t3: '_:y <http://www.w3.org/2000/01/rdf-schema#comment> "Hello"'
>
> I think all of the are equivalent, but the equivalence of t1 and t2
> (where the difference is just whitespace), seems somewhat different from
> that between either of them and t3 (where the difference is in blank
> node labeling).
>
> Should we just define a single standard "equivalence" of g-texts, or do
> we need to allow room for there being several different kinds?
Why would anyone need different kinds?
>
> Maybe the simple notion is "semantic equivalence" of g-texts, which I
> might define as: T1 and T2 are semantically equivalent iff the RDF
> graphs produced by correct parsing of either of them are
> indistinguishable.
>
> -- Sandro
>
>> Pat
>>
>>>
>>> There's a related problem I don't know if we can or should address,
>>> which is how to deal with websites which use cookies or other
>>> information (IP address, browser sniffing, etc) to customize content.
>>>
>>> Does AWWW deal with these at all? Not that I recall.
>>>
>>> For an RDF example, I could make it so http://hawke.org/ip returns
>>> something like
>>>
>>> { <> eg;currentClientIP "128.113.1.1" }
>>>
>>> ... but returning your actual IP address. Given the right cloudhosting
>>> infrastructure, I could meaningfully, and perhaps usefully, return two
>>> different non-equivalent g-texts (ie g-texts for different g-snaps), at
>>> the exactly same moment in time.
>>>
>>> So, I think the model of web addresses identifying g-box which contains
>>> one g-snap at any point in time is as good as REST, and probably good
>>> enough, but still not perfect.
>>>
>>> -- Sandro
>>>
>>>
>>>
>>>
>>
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>>
>>
>>
>>
>>
>
>
>
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Received on Sunday, 20 March 2011 01:30:07 UTC