OWL Reasoning Framework over Big Biological Knowledge Network

Algorithm 3

Efficient OWL reasoning algorithm based on MapReduce.

Map(key, value)

   // key:linenumber(irrelevant)

   // value:instance triple

   PID = PCS·getPID(𝑡𝑟𝑖𝑝𝑙𝑒·predicate);

   //get the PID of the triple

  If   PID==−1   then

   return;

  end if

  if   PID==(len−1)&len%2==1  then

   emit(null, triple);

   return;

  end if

  if   PID%2==1  then

    𝑘𝑒𝑦=(PID−1)+“_”+𝑡𝑟𝑖𝑝𝑙𝑒·getSubject();

  else

    𝑘𝑒𝑦=PID+“_”+𝑡𝑟𝑖𝑝𝑙𝑒·getObject();

  end if

  emit(𝑘𝑒𝑦, 𝑣𝑎𝑙𝑢𝑒);

Reduce(key, value)

   // key:join key

   // value:triple

   𝑠𝑢𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡 = empty;

   𝑜𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡 = empty;

   len=PCS·length;

  for each 𝑡𝑟𝑖𝑝𝑙𝑒∈𝑣𝑎𝑙𝑢𝑒   do

    PID = PCS·getPID(𝑡𝑟𝑖𝑝𝑙𝑒·predicate);

   if   PID%2==1  then

      𝑠𝑢𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡·add(𝑡𝑟𝑖𝑝𝑙𝑒·subject);

   else

      𝑜𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡·add(𝑡𝑟𝑖𝑝𝑙𝑒·object);

   end if

  end for

   𝑛𝑒𝑤_OPC=ComputeOPC();

  for each 𝑠∈𝑠𝑢𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡   do

   for each 𝑜∈𝑜𝑏𝑗𝑒𝑐𝑡𝐿𝑖𝑠𝑡   do

     emit(null, triple(𝑠, 𝑛𝑒𝑤_OPC, 𝑜));

   end for

  end for