Currently, each rule depends on all the existence of input files, which means that the input files have 'and' relationship. Is it possible to support the following case:
'fileA' and 'fileB' or 'fileC' and 'fileD'
If would be useful if two different types of input files are equivalent. For example, '.fastq' and '.fq'
Furthermore, is it possible to add logic flow control in the rules? For example, add another type of rules which support logic control flow. Well, I don't know how to combine this with the current philosophy nicely.