Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

In article <NYqxe.135226$KN7.7252062_at_phobos.telenet-ops.be>, jan.hidders_at_REMOVETHIS.pandora.be says...
> VC wrote:
> > "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> > news:IVhxe.135039$l56.6861917_at_phobos.telenet-ops.be...
> >>Data values are special objects that have one or more representations
> >>associated with them by which they are identified.

[cut and paste]

> Lexical objects are representations of values. Which is slightly
> different from the definition above because there is equivalence
> relation defined.

So a data value and a lexical object is not the same? A data value can have one or more representations, and a lexical object is such a representation?

> > What's that supposed to mean ? 'Value' is just an element of a domain (data
> > type), like, say, '1' is_a_member_of Integer. Are you proposing a new
> > definition of 'value' ?
>
> 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*? The type of the representation, i.e. string or integer? Are there any restrictions on what types can be lexical object types? What are those restrictions based on?

-- 
Jon