Re: [Graphs] g-text equivalence

On 20/03/11 00:16, 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.  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.

Same value (value-equality = bNode-isomorphic set of triples), different 
lexical forms.

 Andy

Received on Monday, 21 March 2011 09:25:24 UTC