[galaxy-dev] Order of element in datasetcollection "List"

Hi all, I've created a tool which takes a collection List as input. This tool iterate on this collection with a "for" loop. I'd like to know the order of my datasets in this collection for the next treatment in my tools.

For example, when I take dataset number 1 and number 2 and number 3 to create my collection. When I iterate on it : what is the first element? the number 1 or the number 3. I ask it because I've seen that when a tool works on a dataset collection, the first job in the history (number of dataset in history is the lowest) ran on dataset number3 and not on dataset number 1 as I expected !

Thanks in advance.

Julie Chevalier