From their early documents, it looks like the KDE4 developers got out to create exactly what you describe. But they created something with very little semblance with this. What you describe is hard, and may not be possible to define well enough for implementing. It's good to know that some people try it, maybe someday somebody will get there.

But, anyway, no you'll still need a filesystem to organize the data you use on each task. Do you use only one level of directories?