- From: Steve Harris <steve.harris@garlik.com>
- Date: Mon, 10 Jun 2013 11:48:05 +0100
- To: Pat Hayes <phayes@ihmc.us>
- Cc: "Sven R. Kunze" <sven.kunze@informatik.tu-chemnitz.de>, public-lod@w3.org
On 2013-06-09, at 20:36, Pat Hayes <phayes@ihmc.us> wrote: ... >>> - value uknown (it should be there but the source doesn't know it) >> Actually that piece of information could be written down in a RDF Schema graph like this: > > It can be written far more simply in RDF just by using a blank node: > > :a :p _:x . Yes, a blank node is probably the closest thing to a SQL NULL in RDF. Though it would be safer/clearer to write: :a :p [] . To emphasise the (NULL = NULL) → FALSE behaviour, which is key to the uses of NULL in SQL. However, the convention in RDF is just to omit the property for that subject where something is unknown - as others have said. - Steve -- Steve Harris Experian +44 20 3042 4132 Registered in England and Wales 653331 VAT # 887 1335 93 80 Victoria Street, London, SW1E 5JL
Received on Monday, 10 June 2013 10:48:33 UTC