Thank You, McKenzie, but that is not what I'm looking for.
My user of the gallery d'ont know the name of the keyword to look for. Maybe he sees one random picture and regarding this he becomes knowledge of the name of the author. Then he look in the categories (or in the listing of a cms part) for the name of this author, and with a clic, all pictures of this author appears.
The exhibitions are published on the site in a way I do not yet know, it is a text. But I can not instruct the user to take the exhibition name and as a user make a search!
For looking for all the pictures of an exhibition, I have to give the oppurtunity to clic easily on a exhibition name ( I thought that this could be another category without loading the data a second time, otherwise sorted) and in the same way must appear all pictures of this authors inside this exhibition. (Can be that there is one exhibition of more than one author, so by the exhibition name I look for all the works of these authors in one named exhibition.)
For the moment, the question remains how I can in the best way organise data on the coppermine database and if possible make the much I can inside it.
From your answer, I suppose the way is the definition by keywords as suggested.
But the user cannot act as the admin, and he would not have the idea to make a search with the exhibition name.
The question is how to acces to all pictures by name of the author AND also by the exhibition-name as an second acces way.
In my idea I thought at something like making other categories labeled with the name of the real exhibition, but I will not put into it a second time all the data needed, that would be double work and space. Instead I would like to to load inside this exhibitionname-categorie a kind of link or other reference - maybe a keyword fixed before - to call up automatically all the pictures belonging to this exhibition which is shown in the manner of an additional category.
But even if I would install - I should at the end -a cms system as drupal, with text content to show listings of the exhibitions and the authors represented too, there is always this question of referencing the same picture data by more than one relation (author AND exhibition) .
I hope it is now a little more clearer what I am looking for?
May be there is no possibility other than keyword referencing. In this case, I need to know if without programming I can in a cms system (maybe minicms) have a link o something which can give to coppermine the "keyword" to look up for the right serie of pictures.
regards
GH