examine function-derived attributes

I wonder if SQL-style views could be superseded by function-based attributes. I imagine the function signature would look something like this:

```haskell
f :: RelationTuple -> Atom
```
where the tuple is the current tuple context to be used for deriving new attributes. This could also be used with grouping for

This would allow derived columns to be conveniently attached to relations without incurring a storage cost.

I need to investigate if such a feature would break any of the laws involving data independence or constraints.