Thanks for the citation, didn’t know that such a thingy exists.
Just a remark on Craft of Prolog by Richard O’Keefe.
If somebody wants an intro into fixpoint calculations
for for example Datalog. You find that also in the 1990
book, just the next sections after ord_union/3. The above
amateur introduction is a little heavy compared
to what Richard O’Keefe presents in his book.
Another likewise introduction could be this XSB tutorial:
Trie-Terms for Sets and Prolog Databases
David S. Warren - ?date?
https://github.com/GunterMueller/XSB_Prolog/blob/e72d74b627a9e4014937abca7941589b27047319/Sources/xsb-code/XSB/lib/prolog_db_doc/prolog_db.pdf
Its hidden inside the source forge distribution of XSB
Prolog, a file by the name prolog_db.pdf. Don’t know
exactly how to cite it.