Re: The Wikibook on Category Theory

["Björn Gohla" <bgohla@mat.uc.pt>]

On Thursday August 20 2009, John Baez wrote:
> Andrew Salch wrote:
>
>  I often find that I need to know if certain kinds of limits, or colimits,
>
> > or injective envelopes, etc. etc. etc. exist in a particular category,
> > and having some central database to look at (which would hopefully tell
> > me what I need to know as well as cite whatever paper the result was
> > proved in) would be a lot quicker than having to either search the
> > literature for such a result or try to re-prove the result myself. Does
> > anyone know if there have been any attempts to compile such a database?
>
> I don't know of any such attempts.  I've always wanted such a database!  An
> obvious place to create it is on the nLab.  I just started one:
>
> http://ncatlab.org/nlab/show/database+of+categories
>
> but it will only become interesting after a while.
>
> If everyone here contributes an entry or two today, it will be interesting
> by tomorrow!
[...]

well, ultimately it would be interesting to have a categorical analogue to 
«counterexamples in topology». 

--
regards,
björn




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