Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Mon, 04 Jul 2005 20:13:10 GMT
Message-ID: <qLgye.137278$Nn7.7012386_at_phobos.telenet-ops.be>
>
> Let me try to sum up.
>
> A value has one or more representations.
Date: Mon, 04 Jul 2005 20:13:10 GMT
Message-ID: <qLgye.137278$Nn7.7012386_at_phobos.telenet-ops.be>
Jon Heggland wrote:
> In article <NBAxe.135734$rx6.7273595_at_phobos.telenet-ops.be>,
> jan.hidders_at_REMOVETHIS.pandora.be says...
>
>>>>Not really, I'm restricting it slightly. I'm using the one that says >>>>that a value is something that (1) has one or more representations, >>>>i.e., can be encoded in memory and (2) is identified by that encoding in >>>>the sense that some equivalence relation over all possible >>>>representations is defined and each value corresponds to an equivalence >>>>class defined by it. >>> >>>This sounds just like D&D's definition in TTM. But a lexical object is >>>not a value, it is the representation of a value? What then is a lexical >>>object *type*? >> >>A set of values.
>
> Let me try to sum up.
>
> A value has one or more representations.
Yes, but note that that was true in *my* definition of value. In ORM terminology the notions of value and representation are usually considered synonymous.
> A lexical object is a representation, not a value.
Again, under my definition of value. In ORM's vocabulary this would not be true.
> A lexical object type is a set of values.
Yep, although it would probably have been less confusing if I would have said it was a set of representations. My apologies for that.
- Jan Hidders