yeah happy.barney,

I was exploring that way right now.
I will just allow rules file to be provided as a parameters (loaded at runtime) to the "rule engine" script.

Like that I can monitor more than one folder (that will be considered as queues like suggested by roboticus) for new images.
Each folder will need different processing.
Images will pass from one folder to an other, giving me my workflow.

That will also give me kind of multi processing.

Sound's good to me !

Thank's for your suggestions !