Forum OpenACS Development: Response to Multiple package instances - correct behavior on instance deletion?

Don, on "dismounting" packages, yes, the Site Map already supports
that.  It's not immediately obvious, but "mounting" and "unmounting"
packages just moves an existing pacakge instance around to different
URLs, without otherwise changing the instance in any way.  You can
also have the same instance mounted at more than one place.

When you click "new application", on the other hand, a new package
instance is created.  (If the pacakge is a "singleton" and already has
one instance, then that package will not show up in the list of
possible new applications to create.)  And then even if you unmount
that instance, you still have to go to "unmounted applications" and
delete the instance, in order to really get rid of it.

That all seems as it should be to me.  However, as far as I know,
there is no hook to run an "instance create" or "instance delete
script", or anything like that.

At the lowest, package install level (controlled from the APM), there
are the load and drop sql scripts, which I imagine are sufficient.
(At least, they've been sufficient for me so far.)  And at the
highest, URL mapping level, there's probably no need for hooks to do
anything special upon mount/unmount of a package.  But at the middle,
package instance create/delete level, there's nothing, and I'm
guessing there probably SHOULD be some sort of hook there to do
package-specific stuff.  But I haven't looked into it carefully.

(Personally, as far as the Site Map UI goes, I think it's a mistake to
complicate the terminology by saying "new application" when what we
really mean is "create a new instance of an application package".
Better to use the precise term and teach admins what it means, then to
use some vauge "friendly" sounding term that could mean anything.)

As for joining your merry band, well, I think I have to at least
download Postgres and the OpenACS 4 codebase and try them out first.
All of which is on my todo list - no promises, but I do look forward
to it.  :)

On the Static Pages package, I'm probably going to try some solution
to the multiple trees issue soon.  (I've already done some minor stuff
to make it work correctly with PDF files and arbitrary MIME types -
this is on ACS 4.2 of course.)  But I haven't decided yet whether I'll
try the muliple instances way of doing it yet or not.  So I'll give
Dave a holler once/if I actually do something there, rather than just
talking about it.  :)

The general-purpose abilitiy to map file-system content to the CR
should be very cool - sounds much cleaner than the current Static
Pages solution, which is to load a copy of all the content into
Oracle, and periodically run a proc to re-scan, diff, and re-stuff
anything modifed into the CR in Oracle again.