Vicious Circle Principle and Logic Programs with Aggregates
  The paper presents a knowledge representation language $\mathcal{A}log$ which extends ASP with aggregates. The goal is to have a language based on simple syntax and clear intuitive and mathematical semantics. We give some properties of $\mathcal{A}log$, an algorithm for computing its answer sets, and comparison with other approaches. 
Michael Gelfond and Yuanlin Zhang
cs.AI