[Nepomuk] syncing nepomuk <-> exif metadata: recent changes, storage service hooks?

[Kristian Rink]

Folks;

am about to play with PyKDE4/Nepomuk bindings and pyexiv2, trying to come up 
with some script to take image metadata (mostly keywords and comments) stored 
in Nepomuk and write this back to the image headers (EXIF, IPTC, XMP, ...) in 
case the file in question does support that. It generally works and doesn't 
seem rocket science as Nepomuk API seems rather straightforward about that, 
leaving figuring out which images should be treated like that as the only real 
problem, as running such a script across a larger digital photography 
collection doesn't seem a good idea.

Two approaches I had in mind:

(a) check Nepomuk service to get a list of image resources which have recently 
(since last checked?) seen a metadata update,  or

(b) hook some handler / extension into Nepomuk Storage Service to 
automatically do this sync whenever some kind of image resource is being 
updated.

So to ask: Is any of these approaches doable with Nepomuk? Is there some way 
to query for (file) resources that have seen a metadata update, say, in the 
last n hours? Is there some way to add extensions to Nepomuk services to 
trigger external actions whenever some resource of some sort is about to be 
updated, preferrably using PyKDE4?

Thanks in advance and all the best,
Kristian