Re: A Logical Model for Lists as Relations
Date: Wed, 10 May 2006 16:47:59 GMT
Message-ID: <3Po8g.5966$A26.151364_at_ursa-nb00s0.nbnet.nb.ca>
Marshall Spight wrote:
> dawn wrote: >
>>Marshall Spight wrote:
>>
>>>What about imperative operations? This is a bit more complicated.
>>>We have to consider whether we want to enforce the usual
>>>list semantics, where for example if we delete an element, the
>>>higher indicies are accordingly reduced.
>>
>>You likely want both operations - a delete and a ripple delete. A
>>deleted list value without the ripple delete would make that value a
>>"2-valued-logic null".
>
> An empty set.
Marshall,
Does it surprise you at all that one of the newsgroup's resident cranks not only fails to question the logical requirements but jumps straight to imagined physical requirements?
>> You wouldn't want to have only the ripple
>>delete in case there is an application need to remove a value in one
>>transaction before "replacing" it in another. No need to renumber,
>>only to do it again with an insert.
>
> What's wrong with "update" in that circumstance?
I suggest the appropriate challenge is much more basic than "update" vs. "delete/insert". The appropriate challenge is: "What possible relevance does this have to the logical model or to any theoretical basis for the type? What possible relevance does this have to the concern for correctness?"
>>By the way, what are your goals/requirements for reinventing this wheel
>>-- what are MS, Intersystems, IBM... not doing that you want to do, or
>>are you just trying to roll your own? Just curious. One guess is that
>>you want declarative constraint handling, perhaps? I don't know if
>>anyone has that in combination with list-valued attributes.
> > Well, yeah I do want to roll my own. From the beginning I've wanted > a more algebraic algebra, more general declarative constraint > handling, more embedding of proofs in code, higher order > functions, stuff like that.
Does it surprise you at all that the resident crank has no concept of abstract thought and can think only in terms of existing products and concrete examples? Received on Wed May 10 2006 - 18:47:59 CEST