Thanks for you're reply. I already was afraid of that :(
Maybe you (or someone else) can help me think of another solution for my problem? I'll try to explain the situation to make things clear.
I'm working on a site for a small low budget non-profit/volunteer organisation. They have just a small internet-budget and very little storage space. However they want to be able to have different headerimages on different pages and these images have to have some copyright-notices in the alt-tag (mostly creative commons). And of course: as soon as they get tired of one, they want to be able to trade a headerimage for another.
So I thought of the following set of solutions:
1) It seemed to be wise to add the copyright-notice to the image-table with dataobjectdecorator (at least: copyright and image belong together and this way the image with the (c)-notice can be reused in other situations on the same site). So I tried to make it possible to edit this db-field from within the dataobject-popup in de DOM, but didn't succeed yet.
2) The next thing that seemed handy was that if the connection of a page to the dataobject (connecting to an image) is deleted, the image will be deleted (this saves serverspace). I'm sure some severe coding will make this possible, but it's way over my head.
3) As the dataobject is only used for the link between page and image, why not cut it short and go directly from page to image. However: the user should be forced to see the add-copyright-notice-popup, instead of going the somewhat longer way through the files&images-tab (I'm always preparing for lazy users).
As point 3 is not possible (yet), I'm back to the 1+2 combination. But as said: that's the option that's beyond my capabilities. So any help is appreciated.