I'm relatively new to Arch, although I've been using various Linux distributions (mostly Debian/Ubuntu, early Fedora (2 - 4)).
However, I came across the guidlines mentioned above, stating that web-apps (such as phpMyAdin etc...) should NOT be installed in /srv/http, but must install in /usr/share/webapps.
I must admit, that I cannot grasp the underlying rationale. The FHS states that everything beneath /usr/share is considered to be read-only architectute independant data.
Of course "shareable and architecture independent" is true for web apps written in e.g. PHP.
However, according to my opinion a web app's files aren't necessarily readonly, because one might need to adapt files like "config.inc".
Here's the only reason to put those files beneath /usr/share/ that came to my mind: Because the FHS states /usr as beign read-only this partition could be mounted as readonly, possibly protecting the web app's files from being tampered with.
Is this the motivating rationale behind this guidline?
I'm sorry, I don't know the answer to your question, but I do remember when the switch happened, when web applications were moved from "/srv/http" to "/usr/share/webapps".
I use WordPress and ZenPhoto. It was around that time that I read some comment from somewhere about how pacman kind of make web application maintenance awkward. Since then, I've been installing / upgrading WordPress and ZenPhoto "by hand" without using pacman, and my life has been SO much easier.
If you're interested in more information, my "document root" (or whatever it's called) is at "/home/http", owned by the "http" user. WordPress has a built in upgrade feature that is blindingly simple to use, and ZenPhoto just involves me unpackaging a tarball over the old directory.