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Re: blank nodes question

From: Graham Klyne <gk@ninebynine.org>
Date: Mon, 28 Jul 2003 09:20:45 +0100
Message-Id: <>
To: Bob MacGregor <macgregor@ISI.EDU>, www-rdf-interest@w3.org

I agree with you... I was trying to acknowledge the other point of view, 
which has been expressed in the past.


At 19:32 27/07/03 -0700, Bob MacGregor wrote:
>At 10:03 AM 7/27/2003 +0100, Graham Klyne wrote:
>>At 20:01 26/07/03 +0100, Peter P. Jones wrote:
>>>I have a question about blank nodes in RDF that's probably not as
>>>naive as it sounds.
>>>Q: Why are blank nodes necessary?
>>There is, I think, a sustainable argument that blank nodes are not 
>I beg to differ.  Blank nodes are absolutely necessary.
>Consider translating an XML file into RDF, where typically
>none of the incoming resource nodes have URI's.  You have two choices, you
>can use blank nodes to represent them, or you can use (globally
>unique) URI's.  If you use URI's, then you need a scheme for
>generating them so that (1) you don't clash with other uniquely
>generated nodes, (2) you need to figure out how to label
>the nodes each of the subsequent times that you load the same
>graph, (3) you still need a scheme to know that these nodes are
>semantically "blank", so that your application can avoid generating
>"pointers" to them.  Its not safe to reference the URI's of blank
>nodes, since typically they won't recur the next time you load, or
>if they do recur, there is no way to guarantee that they denote
>the same node they did the first time.
>So, you can have blank nodes, or you can have a maintenance
>nightmare.  The choice is yours.
>Cheers, Bob

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Monday, 28 July 2003 07:03:21 UTC

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