- From: Bob MacGregor <macgregor@ISI.EDU>
- Date: Sun, 27 Jul 2003 19:32:13 -0700
- To: Graham Klyne <GK@ninebynine.org>, "Peter P. Jones" <ppj@concept67.fsnet.co.uk>, www-rdf-interest@w3.org
At 10:03 AM 7/27/2003 +0100, Graham Klyne wrote: >At 20:01 26/07/03 +0100, Peter P. Jones wrote: > >>Hi, >> >>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 >*necessary*. 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
Received on Sunday, 27 July 2003 22:32:29 UTC