W3C home > Mailing lists > Public > semantic-web@w3.org > December 2012

Re: Well Behaved RDF - Taming Blank Nodes, etc.

From: Steve Harris <steve.harris@garlik.com>
Date: Wed, 19 Dec 2012 18:10:26 +0000
Cc: Lee Feigenbaum <lee@thefigtrees.net>, Pat Hayes <phayes@ihmc.us>, David Booth <david@dbooth.org>, semantic-web <semantic-web@w3.org>
Message-Id: <EE1BFFAF-C126-4628-A0A7-B18C99FCC2FA@garlik.com>
To: Henry Story <henry.story@bblfish.net>
On 2012-12-19, at 17:50, Henry Story wrote:
> 
> On 19 Dec 2012, at 18:43, Steve Harris <steve.harris@garlik.com> wrote:
> 
>> On 2012-12-19, at 16:36, Lee Feigenbaum wrote:
>>>> In any otherwise you end up with names that are just complicated blank nodes, and you
>>>> then have exactly the same problem as blank nodes, except you just end up growning and
>>>> growing your names as you go along.
>>> 
>>> Well, except they don't have the same problems as blank nodes: UUID URIs are stable from one query to the next and can be linked to and referenced across document/database-context.
>> 
>> Yes, this is the key problem with bNodes, which means you have to be /really/ careful about how and when you use them.
> 
> No, its' the opposite. This is a key problem with UUIDs as I argued in my later mail
> http://lists.w3.org/Archives/Public/semantic-web/2012Dec/0097.html

Yes, but I don't buy your arguments.

You can't "prove" that you "created" some http: URI either, unless the document is signed by an unrevoked key, and that works just as well for any kind of URI.

Also, you say "If you use a UUID you could accidentally make a UUID that someone else has already used." well, it's either not a UUID (e.g. a bogus implementation) or there's some statistically insignificant chance http://en.wikipedia.org/wiki/Universally_unique_identifier#Random_UUID_probability_of_duplicates
neither of those cases is very relevant.

> Not every thing that looks like a URI really works like one. For example file:///... URIs 
> usually are not global identifiers, and even though software accepts it, it's just a hack 
> people use to get around software that forces them into this kind of situation. 

There are valid uses for file: URIs, but yes, you have to be careful.

> UUIDs are not a good way to go. They make it look like there is agreement, when in fact
> conceptually things are just as broken.

How does that relate to bNodes? Software doesn't [typically :)] have opinions about the appearance of identifiers.

- Steve

>> We have local hacks to get round the issue, but that's not great. RDF 1.1 bNode skolemisation provides a more generic solution.
> 
> Something I'd have to look into.
> 
>> 
>> - Steve
> 
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> Social Web Architect
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> 

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Received on Wednesday, 19 December 2012 18:10:55 UTC

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