Pipeline documentation

[Gianugo Rabellino]

I'm about to finish a small refactoring of the (caching) pipeline 
optional "expires" feature, which allows to override the cache 
algorithms and force an explicit TTL at the pipeline level.

Now, I want to fully do my homework before committing, so I'm more than 
willing to write some docs, but I don't really know what is the better 
place to start. My alternatives would be:

0. expand performancetips.xml where there is already some documentation 
on it (this has to be done anyway)

1. A formal description as per other sitemap components under 
userdocs/pipelines/cachingpipeline.xml

2. An informal howto under howto/howto-pipeline-expires.xml
3. A Wiki page
Where do you think it fits best?
TIA,
--
Gianugo Rabellino
Pro-netics s.r.l.
http://www.pro-netics.com