Priors and BDe score

• We need: prior counts ?(..) for each network structure G

• This can be a formidable task

  • There are exponentially many structures…

Possible solution: The BDe prior

• Use prior of the form M0, B0=(G0, ?0)
  • Corresponds to M0 prior examples distributed according to B0
• Set ?(xi,paiG) = M0 P(xi,paiG| G0, ?0)
  • Note that paiG are, in general, not the same as the parents of Xi in G0. We can compute this using standard BN tools
• This choice also has desirable theoretical properties
  • Equivalent networks are assigned the same score

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