@InProceedings{Torre1997,
  Title                    = {Prohairetic Deontic Logic (PDL)},
  Author                   = {Leendert W.N. van der Torre and Yao-hua Tan},
  Booktitle                = {In Proceedings of the AAAI Spring Symposium on Qualitative Approaches to Deliberation and Reasoning},
  Year                     = {1997},
  Publisher                = {AAAI Press},

  Abstract                 = {In this paper we introduce Prohairetic Deontic Logic (PDL), a preference-based dyadic deontic logic. An obligation `A should be (done) if B is (done)' is true if (1) no -A/\B state is as preferable as an A/\B state and (2) the preferred B states are A states. We show that the different elements of this mixed representation solve different problems of deontic logic. The first part of the definition is used to formalize contrary-to-duty reasoning, that for example occurs in Chisholm's and Forrester's notorious paradoxes. The second part is used to make dilemmas inconsistent. PDL shares the intuitive semantics of preference-based deontic logics without introducing additional semantic machinery such as bi-ordering semantics or ceteris paribus preferences.},
  Url                      = {http://icr.uni.lu/leonvandertorre/papers/jelia98.ps.Z}
}