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Number of Transitions Aggregate Clarifications

SambsivaReddy Appireddygari

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05/25/2016 - 23:09

Hello,

Number of Transitions Aggregate description provided in section 5.4.3.24 of OPC UA Specifications:

The earliest transition shall be calculated by comparing the earliest non-Bad value in the interval to the previous non-Bad value.

A transition occurred if no previous non-Bad value exists or if the earliest non-Bad value is different

With reference to the above description, I have the following questions.

1.Is the Previous non bad-value refers to the same processing interval or previous interval last non bad sample?

2. Do we need to keep track of previous interval samples to evaluate the aggregate for current interval?

3.Do we need to use bounds? If so what bounding strategy(Interpolated vs Simple ?)

3. Do we need to consider data points with Uncertain quality?

4. The following Use Bounds description is not clear. Could you please explain?

Use Bounds

Custom, a non-Bad value prior to the interval is used

With reference to output (Section A.21.4) against Historian1 , I need clarifications.

1.Why the first interval has result as 0? where I am expecting result as 1

12:00:00.000

Good, Calculated, Partial

2.Why the below interval has result as 1? where I am expecting result as 2

12:01:20.000

Good, Calculated, Partial

Thanks & Regards

Samba

Paul Hunkar

Cleveland, Ohio, USA

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06/08/2016 - 10:25

Samba,

Some answers:

There are three possible overall statuses - Good, Uncertain or Bad. In the specification, it will refer to these states, but sometimes it will reference Not-Good or Not-Bad. These are used when Uncertain is to be included. i.e. Not-Bad means "Uncertain or Good"

The previous value can be in the previous interval or a number of intervals back. Think of it as a bounding value - what is the value at the start of the interval - which you might have to go back and find. Since it is looking for a custom bound - in that it is not simple or interpolated - it wants a value - where the value is not-Bad. The normal bounding rule do not apply.

What version of the specification are you looking at? I don't have a section A 21.4 in the released 1.03 spec I'm using. I'm assumming you are looking at Number of transition samples for Historian 1 - which I think has a mistake in it. both in the heading that lists a different interval than what the table is displaying and also with the first record, since the initial value should be counted as a transition. From the spec" A transition occurred if no previous non-Bad value exists or if the earliest non-Bad value is different." I'll take this up with the editor.

Also the last value should be a 2 - again I'll take it up with the editor.

Paul

Paul Hunkar - DSInteroperability