* Adaptation of the grammar to make more regular w.r.t reference space
names placement.
* Implemented Type check
* Implemented prediction of the result set cardinality. This assumes:
+ A space is not infinite, this is required to compute complementary
sets as we can compute the whole space volume.
+ Density is mostly uniform, this allows us to assume the number of
results is related with a constant factor to the volume in space
of the selection.
+ The prediction is approximated by using the most pessimistic
resulting cardinality for each operator, in order to keep the
operation simple, and fast, at the expense of the precision.
* Implemented execution, which calls into a DB abstraction layer. That
layer is currently mostly empty. Execution is also implemented in a
naive way, and should most likely be optimised.
Lionel Sambuc
6ed76e485e