Aggregates provide a concise way to express complex knowledge. The problem of selecting an appropriateformalization of aggregates for answer set programming (ASP) remains unsettled. Thispaper revisits it from the viewpoint of Approximation Fixpoint Theory (AFT). We introducean AFT formalization equivalent with the Gelfond–Lifschitz reduct for basic ASP programs andwe extend it to handle aggregates. We analyze how existing approaches relate to our framework.We hope this work sheds some new light on the issue of a proper formalization of aggregates.
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