Cascalog isn't really datalog. It is a datalog like fragment without recursion but with added negation. Which makes it more like a pretty syntax for conjunctiv

Cascalog isn't really datalog. It is a datalog like fragment without recursion but with added negation. Which makes it more like a pretty syntax for conjunctive queries with negation and thus equivalent in power to SQL. The tree example of the article would thus not be possible in cascalog.