> Serious Datalog environments will identify strictly monotonic programs [...] Yes. And that is extra work that must be done. Admittedly, it probably isn't the

> Serious Datalog environments will identify strictly monotonic programs [...] Yes. And that is extra work that must be done. Admittedly, it probably isn't the "large factor" mentioned by DannyBee. > A Datalog solver with the property that it can run faster on certain classes of input is great; it is not "no longer a Datalog solver". I was talking of a special, user-requested mode in which the user guarantees that the input program they are interested in will not contain certain constructs, and the solver can reject programs that do contain them. A "Datalog" solver that rejects programs containing, say, negation, does not handle the full Datalog language and is therefore no longer a Datalog solver. As an analogy, Clang is a C++ compiler, but passing it the "-xc" flag causes it to reject valid C++ programs, so then it's no longer a C++ compiler (although it is still the same program!).