[Graphs] g-text equivalence

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.  For equivalence, yes, it seems like there's a simple and
obvious meaning of equivalence, but I don't know how to formalize it,
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?

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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Received on Sunday, 20 March 2011 00:16:19 UTC