Editing Prolog (section)

=== Tabling ===
{{main|Tabled logic programming}}
Some Prolog systems, ([[B-Prolog]], [[XSB]], [[SWI-Prolog]], [[YAP (Prolog)|YAP]], and [[Ciao (programming language)|Ciao]]), implement a [[memoization]] method called ''tabling'', which frees the user from manually storing intermediate results. Tabling is a [[space–time tradeoff]]; execution time can be reduced by using more memory to store intermediate results:<ref>{{Cite journal |last1=Swift |first1=T. |journal=Annals of Mathematics and Artificial Intelligence |volume=25 |issue=3/4 |pages=201–240|title=Tabling for non-monotonic programming |year=1999 |doi=10.1023/A:1018990308362 |s2cid=16695800}}</ref><ref>{{cite journal|last1=Zhou|first1=Neng-Fa|last2=Sato|first2=Taisuke|title=Efficient Fixpoint Computation in Linear Tabling|journal=Proceedings of the 5th ACM SIGPLAN International Conference on Principles and Practice of Declarative Programming|date=2003|pages=275–283|url=http://www.sci.brooklyn.cuny.edu/~zhou/papers/ppdp03.pdf}}</ref>
<blockquote>Subgoals encountered in a query evaluation are maintained in a table, along with answers to these subgoals. If a subgoal is re-encountered, the evaluation reuses information from the table rather than re-performing resolution against program clauses.<ref>{{Cite journal |doi=10.1017/S1471068411000500 |title=XSB: Extending Prolog with Tabled Logic Programming |journal=Theory and Practice of Logic Programming |volume=12 |issue=1–2 |pages=157–187 |year=2011 |last1=Swift |first1=T. |last2=Warren |first2=D. S. |arxiv=1012.5123 |s2cid=6153112}}</ref></blockquote>
Tabling can be extended in various directions. It can support recursive predicates through '''SLG resolution''' or linear tabling. In a multi-threaded Prolog system tabling results could be kept private to a thread or shared among all threads. And in incremental tabling, tabling might react to changes.