Tabling Strategies

The above description gives a general characterization of tabled evaluation for definite programs but glosses over certain details. In particular, we have not specified the criteria by which

• a newly issued call is determined to be a producer or consumer, and
• a derived answer to a tabled subgoal is determined to contain information not in the answer set of that subgoal.

Many different measures can be used as a basis for these determinations. XSB supports two distinct measures within its engine, variance and subsumption, and allows users to program other measures in certain cases (see Section 5.4).