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IDProjectCategoryView StatusLast Update
000160310000-011: Historical Accesspublic2012-02-10 17:02
ReporterNathan PocockAssigned ToRod Stein  
PrioritynormalSeverityminorReproducibilityalways
Status closedResolutionfixed 
Fixed in Version1.02 
Summary0001603: Clarification: UpdateDataDetails vs. ReadModified (multiple modified values for 1 timestamp)
Description

Clause 6.4.3.3 describes the ability to obtain the potential for MULTIPLE modified values on a node for a specific timestamp (not a time-range, but a specific timestamp).

Clause 6.7.2.2 describes that inserting data is not possible when a value exists at the specific timestamp.

Clause 6.7.2.3 describes that replacing a value at a specific timestamp is allowed, but makes no mention of whether or not the server must/should archive the previous value.

Clause 6.7.2.4 describes that using update/replace is a combination of 6.7.2.2 and 6.7.2.3.

There seems to be a conflict here? On the one-hand we're saying that you may have multiple modified values at a specific timestamp, and on the other hand we're saying that we wont allow adding values when the historian contains values for that timestamp, or, you must replace the existing value (at a specific timestamp) with a new value. If the calls don't permit adding multiple values at a specific timestamp, and there's no requirement to archive prior values when being replaced, then how can there be a potential for having multiple modified values at a specific timestamp?

Additional Question: Does (or SHOULD) the spec mention the requirement (or not) for Servers to maintain a record of value that are replaced? (I didn't see it) If such a reference does exists then perfect, where is it and could we reference it in the clauses mentioned above?

We have a number of test-cases "on hold" right now awaiting clarification of the intended behavior with regards multiple modified values at a specific timestamp.

I hope this makes sense. Thanks.

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Activities

Nathan Pocock

2011-04-08 22:59

viewer   ~0002596

After reviewing the afore-mentioned topics again, I think that I have determined a suitable place for a clarification. Append clause 6.7.2.4 the following paragraph after paragraph 1:

"A Server is NOT required to archive previous values, i.e. the value being replaced. If a Server does support archiving previous/replaced values then the Server must support the use of the ExtraData bit as described in clause 3.4.6 (Modified values)"

The reference to the clause should be a hyperlink.

I understand the reasoning for the omission of this clarification, i.e. so as to not "require" the functionality. However, I think it is of more value to explicitly state that the functionality is OPTIONAL and if you choose to use then you will be expected to follow the necessary and applicable rules.

Feel free to use the suggested text as-is or as the basis of a new definition. I hope it helps.

Rod Stein

2011-04-25 17:53

developer   ~0002635

TExt reviewed and added as suggested.

Randy Armstrong

2011-05-23 16:41

administrator   ~0002739

Reviewed in Walldorf

Issue History

Date Modified Username Field Change
2011-03-31 19:49 Nathan Pocock New Issue
2011-04-07 16:17 Paul Hunkar Status new => assigned
2011-04-07 16:17 Paul Hunkar Assigned To => Rod Stein
2011-04-08 22:59 Nathan Pocock Note Added: 0002596
2011-04-25 17:53 Rod Stein Status assigned => resolved
2011-04-25 17:53 Rod Stein Resolution open => fixed
2011-04-25 17:53 Rod Stein Note Added: 0002635
2011-05-23 16:41 Randy Armstrong Status resolved => closed
2011-05-23 16:41 Randy Armstrong Note Added: 0002739
2012-02-10 17:02 Jim Luth Fixed in Version => 1.02