Click on the title to obtain a gzip-ed PostScript version of the paper (82K).
This paper presents an implementation of the well-founded semantics in the SLG-WAM of XSB. To compute the well-founded semantics, the SLG-WAM adds three operations to its tabling engine --- negative loop detection, delay and simplification --- which serve to detect, to break and to resolve cycles through negation that may arise in evaluating normal programs. We describe fully the addition of these operations to our tabling engine, and demonstrate the efficiency of our implementation in two ways. First, we present a theorem that bounds the need for delay to those literals which are not dynamically stratified for a fixed-order computation. Secondly, we present performance results that indicate that the overhead of delay and simplification to Prolog --- or tabled --- evaluations is minimal.