Re: What is Aggregation? Re: grouping in tuple relational calculus
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Fri, 18 Feb 2005 23:19:11 GMT
Message-ID: <PJuRd.14977$ow4.1162376_at_phobos.telenet-ops.be>
Date: Fri, 18 Feb 2005 23:19:11 GMT
Message-ID: <PJuRd.14977$ow4.1162376_at_phobos.telenet-ops.be>
Mikito Harakiri wrote:
>
> All of them -- sets, bags, and lists -- have their place in RM. The
> importance is shifted heavily toward the left side: bags are only important
> in the context of aggregation, and lists are even less important as the
> "order by" SQL clause is virtually the only usage for them.
Indeed. Frankly, I fail to see any big difference between our positions.
> Once again, if we loose accociativity, then we have to expand our semantics
> spectrum to admit trees
Not necessarily. Structural recursion over lists is often based on this.
- Jan Hidders