Date: 201501
Local time of day: 0601-1200
Location: ZBW.ARTCC, NH
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Contributing factors: Chart Or Publication; Human Factors; Procedure
Primary problem: Human Factors

Narrative: There we were; FL230 direct ROBUC on the ROBUC1 arrival. We were issued a clearance; 'cleared via the ROBUC arrival; runway 27 transition.' We verified the route in the box matched the charts. I set 11;000 in the window as it was the lowest (final) altitude on the arrival at PROVI. I started a managed descent at 1;000 feet per minute. At FL225; the air traffic controller told us to maintain FL210. He said 'center' does not issue 'descend via' clearances and that we were cleared to fly the lateral path only. I immediately realized my error. The controller was very understanding of the situation. He said this is happening all the time now with the new 'via' clearances and said he normally follows up a cleared via route with 'maintain FL230'. He said he forgot to add it. He apologized for the confusion as did we.This whole 'via' push has added unnecessary confusion in my opinion. When we are tasked with parsing words (innuendos) during critical phases of flight; the program needs to be revisited.As another example; during climb via and descend via check ons; if the controller responds with 'climb and maintain' it is now secret aviation code' for cancel the restrictions. What was wrong with 'cancel the restrictions?' Seems plain to pilots.Now we have: Climb via Climb via except Cleared via and on and on. Cleared via vs. climb or descend via is subtle. All 3 are 'clearances. We all have 'English proficient' on our certificates. It seems plain English would be the best way to communicate. I knew the difference in the clearances; yet this one slipped by both of us. Frustrating and embarrassing.


Second narrative: Center clears us direct ROBUC and to descend to FL230. Once level at FL230 ATC states: 'cleared via RWY 27 transition'. Both pilots erroneously believed we had been cleared to 'descend via' the arrival. We began our descent and ATC called us and told us to level at FL210 and stated that we were not cleared to descend via the arrival but only cleared via the transition routing. ATC informed us that it was 'no problem' and that it happens frequently. So frequently in fact that he usually makes a point of saying 'MAINTAIN FL230; cleared via the runway 27 transition'. He stated that he had forgotten to say it that way to us. ATC then transferred us to the next frequency and apologized to us for the mix up.Excessive use of the word VIA is the problem. It's everywhere these days. Change the ATC to PILOT lexicon to limit its use to only descents or climbs. Or; do what the controller we dealt with usually does: Make it procedure to state 'MAINTAIN FLXXX' if issuing a VIA clearance that is not a DESCEND VIA or CLIMB VIA clearance. This event is our fault as we misinterpreted an ATC clearance. But it's an easy one to misinterpret; and as the controller stated we were not the first to do so. I will pay much closer attention to any clearance that has the word VIA in it from now on.


Synopsis: The flight crew of an A321; after being cleared via the ROBUC RNAV STAR to BOS; began their descent from FL230 to comply with the arrival restrictions. Shortly after beginning descent ATC advised they had not been cleared to 'descend via' the arrival; only 'via.' The reporters vociferously address what they believe is the excessive use of the word via and the ease with which the precise meaning of via clearances can be misinterpreted by busy flight crews during critical phases of flight.