[foaf-dev] beyond foaf:mbox_sha1sum

Norman Gray norman at astro.gla.ac.uk
Tue Dec 22 16:16:12 CET 2009

Steve, hello.

On 2009 Dec 22, at 14:39, Steve Harris wrote:

> On 22 Dec 2009, at 14:26, Norman Gray wrote:

>> I don't think there's any need for a convention.  The URI http://foo is necessarily identically equivalent in function to the URI http://foo/, by virtue of the HTTP spec.  Thus although they don't compare equal as strings, they are explicitly noted as equivalent in section 6.2.3 of RFC 3986 (which includes equivalent in the owl:sameAs sense, though I doubt it would be either necessary or useful to state this explicitly).
> That's not my reading of RFC 3986.
> It says: “Implementations may use scheme-specific rules, at further processing cost, to reduce the probability of false negatives. For example...” then goes on to give an example of some HTTP-specific normalisations.

But that paragraph ends "the following four URIs are equivalent" -- not "might be", or "can be taken to be", but "are".  And it's not itself mandating this equivalence -- I think it's just remarking on an equivalence which is deducible from RFC 2616.

There's a rabbithole opening up here...

It's not that I have a particular attachment to declaring root URIs without trailing slashes (I have no desire to make things hard for you!).  I suppose I'm simply remarking that the equivalence is one of the list of hassles that RDF-consuming software has to deal with (which this broader mbox_sha1sum thread is illustrating is a long and aggravating list!).

For what it's worth, it's the same situation with <mailto:foo at example.com> and <mailto:foo at Example.COM> -- the two URIs are scheme-specific equivalent, and it lands to you as the data consumer to handle that equivalence.  Doing so by normalising the URIs during ingestion, or handling it with owl:sameAs triples, both have difficulties I can appreciate.

But it seems to me that the normalisation effort has to be on your side as the data consumer, rather than on mine as the data provider (the syntactical difference doesn't matter to me -- I'm making true statements whichever form I use).

All the best (and happy christmas/New Year!),


Norman Gray  :  http://nxg.me.uk

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