> Isn't this .. the spreadsheet?You nailed it, it's a spreadsheet - but one that doesn't constraint all data to live on the same application window, but could access and transform it throughout the whole system - just like copy/paste can transfer data from one program to another, where it can be transformed with a different toolset.
Copy/paste is the most fundamental tool in the toolbox of the end user, since it's the only universal* way to transfer data between apps without accessing an API programmatically, so I think it's undeservedly neglected as a tool to build real life practical workflows.
Incidentally, spreadsheets are one of the most versatile and successful End-User Development tools, allowing users to build information systems tailored to their business purposes. A system combining those design capabilities with the flexibility of building system-wide workflows could transcend the current model of siloed apps.
* Intents on mobile devices are similar, but they are not universal - many times the app to which you want to transfer data is not recognized as a valid target for the shared data.