Re: object algebra
Date: Thu, 26 Feb 2004 18:31:14 GMT
Message-ID: <SXq%b.50110$qW2.2819_at_newssvr33.news.prodigy.com>
"Neo" <neo55592_at_hotmail.com> wrote in message
news:4b45d3ad.0402242201.72ab2c26_at_posting.google.com...
> Since at design time, it is not possible to know the future, according
> to the above, in RDM a relation becomes flawed by the entry of a tuple
> that don't supply all the values.
*sigh*
Then you haven't thought it through - your analysis was incomplete. You can still fix the mistake - but data with a "new" form, like the "missing" attribute, usually isn't new. It's something you didn't think of.
> What if a tuple has an extra/new
> attribute? (In either case, this flaw doesn't occur with TDM)
You may in fact have a new subtype (in which case it can be stored in attributes of the supertype), or may need to define a new relation. There are other possibilities.
> Also now the domain/type EYE_COLOR has tuples "Not Applicable" or
> "Unknown". Doesn't this violate basic set theory?
I don't think so. Why would it? EYE_COLOR is a type you define.
> Color = {red, green, blue} is valid.
>
> Are you saying the following set is valid or allowed in RDM?
> Color = {Red, green, blue, "Not Applicable", "Unknown"}
Yes, it is.
> Is "Not Applicable" a color?
No, it's an EYE_COLOR. Received on Thu Feb 26 2004 - 19:31:14 CET