>> The first scam was Prolog: The language is not really declarative.
The language is not fully declarative. It's something like 90% declarative, but that is not enough to satisfy the purists, who demand 100% purity, or else!
... or else they will stick to their C++'s and their Javas and SQLs, that are, oh, about 0.01% declarative. Because that makes sense, right? If you can't have a perfectly, purely declarative language, throw out the baby with the bathwater and go back to your purely imperative languages.
That kind of criticism has never made any sense and it doesn't make sense now.
>> But the scam is that if you want to do anything serious beyond your stupid positive first-order queries, you need more.
You can't do anything serious with Datalog? Sure you can- you can do machine learning with Datalog: