mapping A :: A2B() : B{
  self.ref1 -> forEach(ref1){
     if (not result.ref2 -> exists (O2 : Object2 | //condition)){
          var O2Object : object Object2{
               //assign all references and attributes
         };
     ref2 += O2Object;
    };
   else if(result.ref2 -> exists (O2 : Object2 | //condition)){
      ....
  }
}