another question: sometimes i want to run solids in a certain order, but i don't want the input from the previous ones. is that possible, or is the only way to force them to run in series to have them use the input from the previous one?

Yes, to enforce the sequence, there must be a dependency, even if the data is not directly used from the downstream solid

cool that makes sense, thanks

It may also make sense to have some sort of placeholder metadata object that acts as a proxy for the implicit dependency (which usually exists if there is a need to enforce sequential execution)

you might also want to use configurable inputs