[nmadden]

Great post! Still working through it, but there is a slight error in the nested diagram at the start. Relational algebra has set difference, which is akin to negation-as-failure, but it lacks recursion. So the positive Datalog and RA circles should overlap without either containing the other. See http://www.lifl.fr/%7Ekuttler/elfe/biblio/datalog-overview-g...

[x775]

Hi there. Thanks so much for your feedback, and good catch! I will update the diagram accordingly.

[x775]

I can no longer edit the parent, but this has been updated. Thanks again!