Re: NULL problem

On Feb 27, 9:32pm, Kerry Sainsbury wrote: > Subject: Re: NULL problem > I was reading about I-Marks and A-Marks the other day. Anybody heard if > they've made any inroads into any commercial databases yet? > > Specifically: I-Marks and A-Marks are just well defined NULLS. > I-Marks indicate a value is "Inapplicable", eg: for a fish a value in a > Hair Color field is inapplicable while A-Marks indicate a value is > "Applicable", but unknown. > > --------------------------------------,------------------------------------- > Kerry Sainsbury, kerry@kcbbs.gen.nz | THE INFORMIX FAQ I don't believe so. If I remember correctly this was Cobb's R2 or R3 document and covers extended null value information. The problem is that it just extends you into 4 valued logic which is even worse to code for than three valued logic. Also there are all sorts of variations that different people might want to get into such as "applicable but unknowable at the moment"!! I suspect that most commercial developers are more likely to follow Date's view which involves highly extended domain information with the capability of building your own domain classes into the database. I believe that Ingres and a couple of others may already have started towards this approach. Cheers - Jim -- ----------------------------------------------------------------------------- Jim Gordon DHL Airways Inc. jgordon@us.dhl.com -----------------------------------------------------------------------------