Tuesday, October 20, 2009

Moving right along

It's always a good feeling when the desk gets cleared of urgent, high-priority tasks so that long-standing (or potentially long-standing) BACnet tasks can be addressed, and I am well into that mode. Unfortunately, these are likely to be controversial.

One is a task from the BIG-EU/WG-Technique (Technical) meeting in Strasbourg, to address the problem of explicitly identifying the version of software/firmware actually tested by a BACnet test lab. There are two properties, Firmware_Revision and Application_Software_Version, that could supply this information, but neither quite fits the bill. I volunteered to address this for discussion by WG-T; looking at it today the best solution seemed to be to refine the description of Firmware_Revision, even noting that the use of this property might be further contrained by a BACnet testing lab's rules for identifying tested revisions. (How about that for punting it into the next court?) It's been sent off; we'll see what happens.

One that's going to be more interesting is a discussion in my "Elevator Monitoring in BACnet" proposal. The last time it was discussed the Objects & Services working group did not like the Building and Room objects (though the Elevator Group, List and Escalator objects seemed okay -- or perhaps we just had not gotten that far). They didn't do anything, they just indicated data structure. Here's how the hierarchy looked:

The committee wanted to use the Structured View object instead -- "structure" is its intended purpose. So I made a stab at it, but found that for a "clean" presentation I needed to use the Character String Value and Positive Integer Value objects currently in public review (until October 26th). Here is how the left-hand side of that structure looks (color-coded functions match the first image):

A lot of extra overhead for a client device. So I tried a "dirtier" approach in which object count goes back down, but it will require changes in the existing standard and has risks:

It will be interesting to see what the committee says.

Ain't BACnet fun?

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