Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

Bob Badour wrote:
>"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message
>news:3e6e53bf.0_at_news.ruca.ua.ac.be...
>> Bob Badour wrote:
>> >"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message
>> >news:3e6e4547.0_at_news.ruca.ua.ac.be...
>> >> Bob Badour wrote:
>> >> >"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message
>> >> >news:3e6da66b.0_at_news.ruca.ua.ac.be...
>> >> >>
>> >> >> I'm not convinced that bags are never needed. [...] And if you are
>> >> >> then going to simulate them with sets then the cost might become
>> >> >> negative because the set-based optimizer might miss certain
>> >> >> optimizations that would have been easier to spot for a bag-based
>> >> >> optimizer.
>> >> >
>> >> >Such as?
>> >>
>> >> Such as combining two iterations over the same bag into one. [...]
>> >
>> >If we don't have bags, it is not an issue. Is it?
>>
>> Yes, it is. Because then you have to simulate them and what the example
>> showed is that in that case the same optimization becomes very hard to
>> spot.
>
>Why would I have to simulation them?

Because they exist and are used by mathematicians and others to model all kinds of problems.

• Jan Hidders