Use Case:
Photos are organised in a folder structure by date (by software lightroom/picasa)
Want to run a local webserver to host a web gallery from (already know how to run lamp etc)

I want to be able to attach metadata to the photos (probably through a database not residing in the photos folder) such that they can be tagged/categoried/albumed without affecting the original photos
I want to be able to assign permissions to different albums to set users
I want the software to watch the photo source folder for changes so that new photos are indexed ready for applying metadata and albums.
I'd like the software to handle the rendering of numerous file types (photo formats) as well as video formatts

I am language agnostic so php/python heck even c#, just want software that forfills the requirements. The main reason I am asking this question here as I am unsure what this software would even be called so google searching is quite difficult!

Thanks for reading.