Workflow over the web, best approach with full generalization

The question might sound foolish to some. I am totally new to this workflow concept.

My employer has to give a proposal regarding a complex workflow scenario over the web. We need a document management system where we can use Sharepoint.

And we need a technology with full generalization possible for managing workflow.

Please suggest something killer.

We can even combine other technologies like java and .net . Our primary focus is on .net .

[Apologies, I work for IBM, can't see how this question can be answered without mentioning specific products, so I'm mentioning ours.]

Workflow is a deceptively simple concept. Just pass tasks from person to person, how hard can that be? As we might expect the real world tends to intrude. You need to be able to fine-tune workload, adjust priorities, call external systems, do some actions conditionally, get reports about what's been happening ...

IBM's Lombardi to my untutored eyes looks pretty good, it has Sharepoint integration and I guess is the kind of thing you are looking for. I've got no idea how it stacks up against any competing vendors, but my colleagues who work with it all see pretty enthused.

In summary: This is not a trivial problem space, there are serious products out there because this stuff can get quite complex.