- From: David Booth <david@dbooth.org>
- Date: Sun, 25 Nov 2018 22:13:27 -0500
- To: semantic-web <semantic-web@w3.org>
On 11/24/18 2:08 PM, Pat Hayes wrote: > On 11/22/18 5:49 PM, David Booth wrote: > . . . >> A blank node . . . asserts that there *exists* >> a thing, as explained in the RDF Semantics: >> https://www.w3.org/TR/rdf11-mt/#blank-nodes In contrast, >> an IRI represents *a* thing. I'm sorry to be pedantic >> here, but I mention it because it underscores my point: >> the semantics of blank nodes really *are* subtle -- at >> least to *average* developers. > > Is this idea really hard for anyone? Short answer: Yes! > If URIs are names, then blank nodes are pronouns, like > 'anyone' in the previous sentence. People don't seem to find > pronouns hard or subtle or confusing, or complain that they > have devious semantics. Longer answer: I think an average developer certainly could understand that concept if it were isolated and explained that way. But it isn't. It is only one of *several* concepts that are used in *combination* in RDF. And the implications of the resulting combination are *not* so easy to grok. (Case in point: No middle 33% developer is going to grok the RDF Semantics document, though it is based on simple concepts.) This principle shows up all the time in every scientific field -- mathematics, biology, etc. -- where a few "simple" concepts combine to have consequences that are amazingly hard to understand. But this "existence" issue is a bit of a red herring, because it is not the most significant stumbling block with blank nodes. The most significant stumbling block is around blank node *identifiers". > . . . > However, I agree with your point about bnode > *identifiers*. . . . There is something inherently > contradictory in having an identifier for something which, > by definition, is something which does not identify. Agreed. David Booth
Received on Monday, 26 November 2018 03:13:50 UTC