Tuesday, July 6, 2010

All Quiet on the BACnet Front

Having been away from my work e-mail for a three-day holiday weekend I was dreading what I would find when I logged in this morning. Two surprises: 1) very little e-mail, and 2) absolutely nothing BACnet-related. Well, except for a note sent to the committee chair about the status of a proposal I had drafted and filed before I left Albuquerque.

After the contention and multi-direction split of the committee over its predecessor, it's going to be interesting to see what happens on this one, because it doesn't actually do anything except add a suggestion to the implementer, to wit:

[Change Clause 13.1, p. 290]

It is the responsibility of the COV-server to maintain the list of active subscriptions for each object that supports COV notification. This list of subscriptions shall be capable of holding at least a single subscription for each object that supports COV notification, although multiple subscriptions may be supported at the implementor's option. The list of subscriptions is network-visible through the device object's Active_COV_Subscriptions property. Subscriptions may be created with finite lifetimes, meaning that the subscription may lapse and be automatically canceled after a period of time. Optionally, the lifetime may be specified as infinite, meaning that no automatic cancellation occurs. However, the COV-server is not required to guarantee preservation of subscriptions across power failures or "restarts." Periodic resubscription is allowed and expected expected, at least at the longest interval after the last received COV notification for which it is acceptable for the COV-client device to operate unawares on "stale" COV information ("stale" because the COV-server is not operating, has been removed or has been replaced), and shall simply succeed as if the subscription were new, extending the lifetime of the subscription.

I'm sure there will be quibbles with the phrasing (I'm not completely happy myself), but beyond that we'll see.

(It's good things are slow because I have to write a BACnet-related article due next week.)

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