The substitution to resolve the first two rules on q is θ
7
= {U := Χ; V := X},
which is read "replace U by X; replace V by X." The substitution to resolve
the second rule with the "ghost" on ρ is θ
2
= {U := f{W); V := Since
these substitutions cannot be composed into a single substitution, the apparent
loop will never be realized. •
Conclusion
We have presented a new semantics, the tight tree semantics, for general logic
programs that has advantages over the rule-based semantics in that a larger por-
tion of the Herbrand base tends to be classified as belonging to either the suc-
cess set or the failure set. We have defined a reasonabl ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.