Graph-Based Semantic Web Service Composition for Healthcare Data Integration

Algorithm 2

Backward search.

Input: and are the requested input and output parameters of WS searching (I/O dependency)

Output: is a set of discovered paths of potential web services (sets of operations)

procedure BWS(u,v)

            //V is a set of discovered nodes

          // is a set of queue of ordered pairs of vertices and paths (sets of arcs)

 while do

          //get the ordered pair of vertex and path in queue as

  if has no adjacent arc then   //check if is an origin vertex of a path

       //creating the reverse path of potential services into

            //add into

  else if then        //check if is not equal to input vertex

   for     //to find the adjacent arcs of t through a query “select ?e where {?e head ?t.}”

              //create as a clone arcs set of

           //append an arc e to arcs set

           //find head vertex of arc e from a query “select ?v_i where {?e tail ?v_i.}”

    if is not in then     //check if have not been visited

           //add to the set of visited vertices

    enqueue to     //put order to for the next round in while loop

    end if

   end for

  end if

 end while

 return               //return when is empty

end