Re: Two more FAQ entries

At 16:20 +0200 31.8.04, Lutz Strassburger wrote:
>On Tue, 31 Aug 2004, Alessio Guglielmi wrote:
>  > I don't understand your remark. Take
>>
>>      +----+   +----+
>>      |    |   |    |
>>      a   -a   a   -a
>>       \   |   |   /
>>        \  +---+  / .
>>         \       /
>>          \     /
>>           \   /
>>           a P -a
>>
>>  How am I supposed to turn around this?
>
>like this:
>
>          -a P a
>           /   \
>          /     \
>         /       \
>        /  +---+  \
>       /   |   |   \
>     -a    a  -a    a
>      |    |   |    |
>      +----+   +----+

OK, as I suspected, you have a personal, still not very frequent 
notion of proof net; my problem was to address the frequent notion 
known to the people who frequently ask questions.

As a side remark, I would say: with super-symmetries come 
super-responsibilities (like for Marvel super-heroes). Flipping a 
proof net and getting a refutation net is trivial; after you do this, 
you should also feel the moral obligation of talking about 
*derivation* nets, meaning top-down symmetric objects with non-unit 
premise and conclusion. They represent the natural closure of the 
symmetry you're talking about. And then: what is a correct derivation 
net? Do you have a correctness criterion, sequentialisation, etc.?

What I mean is that a `correct point of view' should be productive in 
some technical sense. I guess we agree, but I still don't see the 
practical benefits of your point of view.

-Alessio