CONFUSING LANGUAGE OF REVISED SEGMENT OF PDC RESULTS IN TRACK DEVIATION AT ARR ARPT FOR A FLT CREW.

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WE REQUESTED PDC CLRNC FROM ATL CLRNC VIA ACARS. THE ATC CLRNC THAT WAS FILED WAS ATL DOOLY4 GRD ADENA1 CLT. WE RECEIVED THE PDC WITH A REVISED SEGMENT -- DOOLY4 GRD UNARM -- NOTE: NOTHING WAS PRINTED AFTER THE UNARM INTXN. WITH THE REVISED SEGMENT WRITTEN THE WAY IT WAS WE ASSUMED THAT THE ARR IN CLT WAS CHANGED TO THE UNARM1 ARR FROM THE ADENA1 ARR. THE UNARM INTXN IS THE SAME INTXN ON BOTH THE ADENA1 AND UNARM1 ARR WITH THE EXCEPTION BEING THAT THE ADENA1 IS AN RNAV ARR WITH A NORTHBOUND TURN DOWNWIND FOR S LNDG RWYS IN CLT. ACCORDING TO CLT ATC CTL WE WERE SUPPOSED TO TURN N AS IF WE WERE ON THE ADENA1 ARR BUT WE HAD THE UNARM1 PROGRAMMED INTO THE FMS WHICH HAS NO TURN NORTHBOUND. CLT ATC GAVE US VECTORS FOR THE ARR AND LNDG. UPON LNDG ATC ASKED US TO CALL THEM VIA LANDLINE. ATC TOLD ME THAT WITH THE REVISED SEGMENT IT IS ASSUMED THAT THE WAY IT WAS WRITTEN WE WERE SUPPOSED TO FLY THE ADENA1 AFTER THE UNARM INTXN. MY REMARK TO CLT ATC WAS AFTER WE RECEIVED THE REVISED SEGMENT WE FLEW THAT NEW RTE AND DID NOT MIX THE REVISED SEGMENT AND THE PREVIOUS ATC FILED ROUTING. THERE IS NO WAY TO TELL WHAT ATC WANTS US TO DO IN THIS INSTANCE AFTER THE UNARM INTXN. AS A MATTER OF FACT THE WAY THE REVISED SEGMENT WAS WRITTEN; DOOLEY4 GRD UNARM; AFTER UNARM WE WERE CLRED DIRECT TO CLT. THE REVISED SEGMENT WAS/IS CONFUSING. SINCE THE UNARM INTXN IS ON BOTH THE ADENA1 AND THE UNARM1 ARR I'M NOT SURE I UNDERSTAND WHY THE NEED TO ISSUE A REVISED SEGMENT WITH THE UNARM INTXN AS A REVISED POINT. THE CONFUSION CAN BE ELIMINATED IF ATL ATC HAD ADDED ADENA1 AFTER UNARM IN THE REVISED SEGMENT. MOST PLTS WILL LOOK AT THE REVISED SEGMENT; PROGRAM THE FMS FROM THAT NEW CLRNC; AND DISREGARD THE ORIGINAL FILED CLRNC. THE WAY THE REVISED SEGMENT WAS WRITTEN; DOOLY4 GRD UNARM; A PLT COULD ASSUME THAT AFTER UNARM THE PLT WAS CLRED DIRECT TO CLT.