Hello,

If we have the following functions and function spaces:

```
V1 = element("Lagrange", "interval", k)
V2 = element("DG", "interval", k-1)
f = Function(V1)
g = Function(V2)
```

we can clearly see that g should be in the same fucntion space with f.dx(0), so can we obtain g from f in the strong form, i.e., g = f.dx(0), or we can only do that using some weak form like:

g * v = f.dx(0) * v

Thanks!