Phase Transitions of Contingent Planning Problem

Algorithm 2

Contingent plan-existence algorithm.

Algorithm CONTINGENT PLAN-EXISTENCE (𝐍,𝐘,𝐁𝐬,𝐀,𝐎)

𝑓𝑙𝑎𝑔=0;

 for each  𝑠∈𝐁𝐬

  if 𝐍⊄𝑠

  then 𝑓𝑙𝑎𝑔=1;

 endfor

 if 𝑓𝑙𝑎𝑔==0

 then return true

 for each  𝑎∈𝐀

  if applicable(𝐁𝐬,𝑎) and 𝐍∩𝑎𝑑𝑑(𝑎)≠∅ and 𝐘∩𝑑𝑒𝑙(𝑎)=∅

  then 𝐁𝐬^′=𝐁𝐬+𝑎𝑑𝑑(𝑎)−𝑑𝑒𝑙(𝑎);

𝐍=𝐍−(𝐍∩𝑎𝑑𝑑(𝑎));

𝐘=𝐘+(𝐍∩𝑎𝑑𝑑(𝑎));

    CONTINGENT PLAN-EXISTENCE 𝐍,𝐘,𝐁𝐬^′,𝐀,𝐎;

 endfor

 for each  𝑜∈𝐎

𝐁𝐬_𝑇=𝐁𝐬∩𝜑⁻(𝑜);

𝐁𝐬_𝐹=𝐁𝐬∩𝜑⁻(𝑜⁻);

     if 𝐁𝐬_𝑇≠∅ and 𝐁𝐬_𝐹≠∅

     then CONTINGENT PLAN-EXISTENCE 𝐍,𝐘,𝐁𝐬_𝑇,𝐀,𝐎∧

      CONTINGENT PLAN-EXISTENCE 𝐍,𝐘,𝐁𝐬_𝐹,𝐀,𝐎

 endfor

 return don’t know

end