Forgetting in Logic Programs with Ordered Disjunction

We present a new forgetting method in logic programs with ordered disjunction (LPODs). To forget a literal means to give it up from the answer sets of the program. There is a known method for doing this in an extended logic program (ELP) by transforming it into another such program whose answer sets have only lost the forgotten literal. However, a naive application of it to an LPOD can produce undesirable results. Our new method avoids these, and ensures that the answer sets of the LPOD, as specified by its so-called split programs, only lose as few literals as are necessary. To achieve this we introduce two new literals "⊤" and "⊥" into the syntax of LPODs and extend the definition of an answer set accordingly.