Theory and Practice of Logic Programming

Regular Papers

XSB: Extending Prolog with Tabled Logic Programming


a1 CENTRIA, Faculdade de Ciências e Tecnologia, Univ. Nova de Lisboa, 2825-516 Caparica, Portugal (e-mail:

a2 Department of Computer Science, SUNY Stony Brook, Stony Brook, New York, USA (e-mail:


The paradigm of Tabled Logic Programming (TLP) is now supported by a number of Prolog systems, including XSB, YAP Prolog, B-Prolog, Mercury, ALS, and Ciao. The reasons for this are partly theoretical: tabling ensures termination and optimal known complexity for queries to a large class of programs. However, the overriding reasons are practical. TLP allows sophisticated programs to be written concisely and efficiently, especially when mechanisms such as tabled negation and call and answer subsumption are supported. As a result, TLP has now been used in a variety of applications from program analysis to querying over the semantic web. This paper provides a survey of TLP and its applications as implemented in the XSB Prolog, along with discussion of how XSB supports tabling with dynamically changing code, and in a multi-threaded environment.

(Received October 04 2009)

(Revised February 28 2010)

(Accepted November 22 2010)


  • Prolog;
  • tabling;
  • implementation;
  • non-monotonic reasoning