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--- controls:protocols:bacnet:qna [2020/10/02 21:27] – old revision restored (2020/09/20 21:08) 207.180.224.141
+++ controls:protocols:bacnet:qna [2020/10/04 00:48] – old revision restored (2020/09/30 16:24) 92.220.10.100
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-====== BACnet Questions and Answers ======
+====== Questions and Answers ======
 Here are a few interesting Q&A gathered from the BACnet mailing list.
@@ Line 29: / Line 29: @@
 - Coleman
-===== DateRange =====
-??? BACnetDateRange every year
-One of our customers wants to setup a BACnetDateRange from 1.November to 30.April. _Every Year_
-In my reading of the BACnet Spec, this is not allowed:
-Chapter 12:
-...Date_List property ...  Both startDate and endDate may be an unspecified date or a specific date only.
-Is there an other solution?
-- Andreas
-!!!
-There is a long and complex history behind DateRanges in Schedules.
-The short version is that the original 1995 language in the standard was not sufficiently
-clear about how DateRanges were intended to work, due to a lack of consensus
-about the wording. Regrettably this caused several incompatible implementations to
-exist in the marketplace. When the SSPC attempted to readdress this issue in the
-standard, the compromise was to make the restriction of “all wildcard” or “no wildcard”
-as the only options for DateRange. This is too bad because there are many DateRange
-wild combinations that are useful.
-The original idea (which was not articulated thoroughly in the standard) was that in DateRanges
-where there are any wildcards, each of the four ranges needs to be treated in a strict
-order of precedence: year, month, day-of-month, day-of-week. The test for something
-being “within the date range” is that it passes four tests in this order:
-. Is today’s year within the range of years?
-and
-. Is today’s month within the range of months?
-and
-. Is today’s day-of-month within the range of days?
-and
-. Is today’s day-of-week within the range of days of week?
-So using Gerhard’s example:
-startdate             year=ANY, month=ANY, day=ANY, dayofweek=Monday
-enddate               year=ANY, month=April, day=ANY, dayofweek=ANY
-To match this range a date must perform these steps:
->since start and end year=ANY it always matches year
->since start and end month is ANY through April this is the same as having said “January through April”
->since start and end day=ANY it always matches day
->since start and end dayofweek is Monday through ANY this is the same as having said “Monday through Sunday”
-So the <<intended>> logic of Gerhard’s example boils down to “is the month between
-January and April inclusive”?
-The key idea, which a lot of people didn’t get because the standard was not clear enough,
-was that the evaluation of range is different when there are any “ANYs” in the 8 fields of the range.
-This is a moot point now, but that’s how we intended for it to work.
-- David Fisher
 ===== max_info_frames =====
@@ Line 106: / Line 47: @@
 - John Hartman
-!!!
-To question 2)
-Devices not supporting READ-PROPERTY-MULTIPLE may significantly slow down the network.
-The reason is:
-- If multiple properties from the same device need to be polled by another deivce (controller or workstation) then individual READ-PROPERTY services need to be issued.
-The amount of extra tokens used when a workstation updates it's status depends on how many properties are read from single devices.
-- Christoph Zeller