Re: Concurrency in an RDB

From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 29 Dec 2006 14:51:24 GMT
Message-ID: <MX9lh.539041$R63.206565@pd7urf1no>

Aloha Kakuikanu wrote:
> Sampo Syreeni wrote:
>

>>Given the current, practical importance of both running text and the RM,
>>I wonder why a) there haven't been any genuine attempts at treating
>>strings, text and language in general in relational terms, or b) why the
>>RM folks won't confess it can't be done, given the current state of
>>knowledge, thereby acknowledging that there is data that just isn't
>>currently amenable to relational treatment.

>
>
> What "text" do you have in mind? A set of strings is formalized nicely
> as Kleene algebra. relational algebra is also Kleene algebra.
>
> Seriously, the parallels between Kleene algebra and relational algebra
> (in Codd's definition, not Tarski:-) are remarkable. If one accepts
> that join and union are the 2 fundamental operators of relational
> algebra, and agrees that Kleene star is somewhat less important
> operator, than both algebras hinge on join and union. The fundamental
> difference is that relational join is commutative, while Kleene's is
> not.
>

I think that exposes half of the question for what it is - not apt. I'd say the other half is simply that an implementation doesn't need to re-prove a theory in order to obey it. Not much progress if they did.

p Received on Fri Dec 29 2006 - 08:51:24 CST