Re: Operationalize orthogonality
Date: Mon, 05 Jun 2006 12:36:25 GMT
Tony D wrote:
> x wrote:
>>"Tony D" <tonyisyourpal_at_netscape.net> wrote in message >>news:1149504303.205324.83320_at_j55g2000cwa.googlegroups.com... >> >>>x wrote: >>> >>> >>>>How complicated! It would not be easyer to follow Mr. Codd advice ? >>>>Domains, not types. >> >>>And the difference between a domain and a type is what ? Precisely ? >> >>The "standard" answer would be "educate yourself". :-)
> Alternatively, you could attempt a non-standard answer ?
The answer depends on whether one accepts specialization by constraint as specifying a new type. If one does, then domain and type are synonymous. If one does not, then a domain is generally a specified subset of some type used in a specified context.
>>I don't know how "precisely" you want me to be.
> As precise as you need to be to point out what you believe the
> difference between a domain and a type is.
>>I would say that my current understanding of this (because I have not yet >>read Codd's 1990 book - which I strongly recommend because I browsed it) is >>that domains do not include any kind of operator.
> So, if domains include no operators, what can you do with them ?
> In this context, I equate the terms domain and type - as mentioned in
> the presentation pointed to elsewhere on this thread. (I don't,
> however, equate classes with domains or types - principally because (a)
> I'm not 100% clear on what a class is exactly, and (b) from what I do
> understand about classes & objects, there is a dynamic element to them
> that I wouldn't expect to find in a domain or type. I am open to
> persuasion on these points.)
- Neither are the OO proponents.
- That comes from the frequent use of 'object' as synonymous with 'variable'. However, 'object' gets used for a lot of different things too.