- From: David Wood <david@3roundstones.com>
- Date: Mon, 3 Jun 2013 09:43:51 -0400
- To: Jan Michelfeit <michelfeit.jan@gmail.com>
- Cc: "public-lod@w3.org" <public-lod@w3.org>
Hi Jan, That's because nulls are generally not represented in Linked Data by design. One "represents" a null by failing to include the relationship. Regards, Dave On Jun 3, 2013, at 4:38, Jan Michelfeit <michelfeit.jan@gmail.com> wrote: > Hi, > I was doing some comparison of relational databases and Linked Data and ran into the problem of representing an equivalent of database NULL in RDF. > > I was surprised I haven't found any material or discussion on this topic (found only [1]) - is there some?. I believe it would be beneficial if this question was answered somewhere for future reference. I started a question on Stack Overflow [2] where I think it will be easier to discover and so that this list won't get polluted. > > I'm aware of the open world assumption in RDF, but NULL or a missing value can have several interpretations, for example: > > - value not applicable (the attribute does not exist or make sense in the context) > - value uknown (it should be there but the source doesn't know it) > - value doesn't exist (e.g. year of death for a person alive) > - value is witheld (access not allowed) > > I would like to known whether there is some *standard or generally accepted* way of distinguishing these cases. If you have an answer, please put it on [2], is possible. > > Thanks in advance, > Jan Michelfeit > > [1] http://lists.w3.org/Archives/Public/public-rdf-wg/2011Nov/0167.html > [2] http://stackoverflow.com/q/16873174/2032064 > >
Received on Monday, 3 June 2013 13:44:54 UTC