McDonnell Douglas Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Confusion
No Specific Anomaly Occurred All Types
General None Reported / Taken
Human Factors; Chart Or Publication; Procedure
Approach assigned us the Quiet Bridge Visual approach for 28R.  We departed ARCHI heading 260 as depicted; and intercepted the 275 course inbound to SFO VOR as depicted.  I had entered the radial and we armed the VOR.  The autopilot intercepted and flew the inbound radial.  The approach page shows altitudes at 20; 15; 10 and 6 DME from SFO VOR; each accompanied with the parenthetical statement '(For Class B Airspace)'.  In my mind; these were only recommended altitudes to keep us above the Class B floor; and I did not attempt to hit each one exactly.  Approach control gave us at least a couple further descent clearances while on this segment; which seemed to be corresponding to the depicted altitudes.  After the ILS glide slope came alive; I followed its descent path fairly closely until intercepting the ILS course inside the San Mateo Bridge; after which I followed it exactly.  The approach resulted in an uneventful landing and rollout with no comments by either Approach Control; or the Tower Controller.  After the flight; the First Officer and I discussed the intent of the Quiet Bridge Visual Approach; and it wasn't entirely clear whether the depicted altitudes were merely recommended; or required - and that is what prompted this report.We are very accustomed to IFR STAR's; which specify altitudes as 'at or below;' 'at;' or 'at or above.'  Although the Quiet Bridge's status as a visual approach implies pilot discretion with respect to altitudes; it nevertheless specifies an exact track to be followed -- which led us to wonder after the fact if the altitudes were expected and not merely recommended. Perhaps the addition of clarifying words such as 'at' or; 'recommended' would solve this ambiguity (as is done on the JFK Parkway Visual approach).
[Raport narrrative contained no additional information].
McDonnell Douglas widebody flight crew reports being confused by the altitudes depicted on the Quiet Bridge Visual approach and whether they are manditory or recomended.