[galaxy-dev] tools to reduce list of datasets.

Hi All, Can someone point me to documentations/ examples of how to write a tool to reduce a a list of datasets back into a single dataset. == What I want to do is process multiple pairs of reads. 1. load all the fastq files. 2. create a list of pairs 3. Run tools of each pair in the list (As a seperate job for each pair) 4. Run a single tool over all the results of 3 at the same time! (One job which takes all the files/ whole collection) as input. thanks in advance Christian