The CERN 26Gev Proton Synchrotron (PS) accelerator complex produces a sequence of different beams in cycles of a duration of 1.2 sec or multiple of it.A Main Control Room operator, supervising the functioning of (part of) an accelerator for a particular beam, needs to coherently display on his workstation the beamdependent data, in 'synchronism' with this particular cycle (within a certain time delay).The classical data collection via synchronous Remote Procedure Calls cannot fully answer to these requirements.The PS Data Subscription Mechanism addresses the above-mentioned problems: 0 it allows a client application in a Workstation to dynamically request accelerator data synchronised to a particular beam; e the client collects data related to the same beam from different front-ends The paper exposes the CERN PS specific requirements, and the solution proposed, based on functional data-groups and providing the additional functionality of monitoring process data (i.e., send on change).