Re: Perhaps an idiotic question

Neo wrote:
>>>First, to make the declaration, your language has to make some sort of
>>>forward reference to the type. Second, to have this exactly as stated
>>>yields a potentially infinite progression of the type. In practical
>>>terms, one would have to settle for a finite recursion because computers
>>>are finite machines. ie. If one serially ungroups the A attribute, at
>>>some finite step, ungrouping would yield an empty relation with
>>>cardinality zero.
>>
>>Thanks for that. I agree about the forward reference but it seems
>>non-controversial, eg., not uncommon, to me and as well about the
>>infiniteness (which might be the aspect that intrigued me). As for the
>>infiniteness, I don't want to distract into what's practical and what's
>>not except to say that we sometimes ignore infinite issues in practice,
>>given enough memory we are sometimes prepared to let things 'fall apart'
>>at some point, eg., crash/fail as long as we never get a wrong answer
>>for the progressions we can handle.

> 
> 
> I think you are saying, since a table is defined after its columns are
> defined, this leads to a catch-22 situation if a column needs to
> reference the table it is in which hasn't been defined yet. Would one
> way around this be, to create the table without the column and then add
> it later?
> 

I didn't intend to suggest that. I think it is possible to define both at once.

p Received on Thu Nov 30 2006 - 03:54:02 CET