I find it interesting that the cross-product is showing up here, as I'm used to applying it to vectors. I'm not sure why it's being used here, or how it's contributing to the queries done by Widom? The form for using SELECT seems to be...
> SELECT attribute FROM relation WHERE attribute has condition
...which is a sort of speaking style that I feel I could learn over the course of this class. I haven't been able to sort out the difference between project and select, as anything project could do, select can do as well?