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IDProjectCategoryView StatusLast Update
000937210000-004: ServicesSpecpublic2024-02-06 16:46
ReporterJeff Harding Assigned ToMatthias Damm  
PrioritynormalSeveritymajorReproducibilityhave not tried
Status assignedResolutionopen 
Product Version1.05.03 
Summary0009372: Bad_LastKnown StatusCode needs clarification
Description

Part 8 table 29 "Operation level result codes for data quality" states that Bad_LastKnow should be mapped to Uncertain_NoCommunications because UA requires a Null value with Severity Bad. I don't see why or where UA makes this statement aside from Part 8. In fact Part 4 is very clearly contradicting this statement. Part 4 states "If the Server has no known value - in particular when Severity is BAD, it shall return a NULL value." The qualify "if the server has no know value" make perfect sense and ensures a server which does a a value (such as the last know value) can use it when Bad.

Part 8 should be fixed to relax the require to always provide a Null when Bad.

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Jeff Harding

2024-01-30 18:01

developer   ~0020736

Discussed the issue during the Jan 30th WG call.

Conclusion is that Part 4 Table 135 DataValue clearly states a null shall be returned when StatusCode is BAD. "The data value. If the StatusCode indicates an error then the value is to be ignored and the Server shall set it to null."

The text in Part 4 "Part 4 states "If the Server has no known value - in particular when Severity is BAD, it shall return a NULL value." should be changed to remove the "if the Server has no known value - in particular when the Severity is BAD" to "When the Severity is BAD"

Jim Luth

2024-01-30 19:49

administrator   ~0020738

I think more discussion is needed on this ideally when Karl, Matthias, Jeff, Paul, Randy and I are present.

Jim Luth

2024-01-30 20:24

administrator   ~0020739

Here is my strawman for updates to Part 4:

https://opcfoundation.sharepoint.com/:w:/r/sites/wg.UA/Shared%20Documents/sg.Core/Meetings/2024/2024-01-30%20Weekly%20Web%20Meeting/OPC%2010000-4%20-%20UA%20Specification%20Part%204%20-%20Services%201.05.03%20Jim%20Luth%20Mantis%20%239372.docx

David Levine

2024-02-05 16:29

developer   ~0020769

Last edited: 2024-02-05 16:31

@Jim Luth
Your strawman includes this: "If a Variable is created and no default value or initial value is available, the StatusCode shall be Bad_NoValue."
Some use cases to consider:
1) Servers can have Variable Nodes with a non-NULL DataValue, which contain timestamps and a Good StatusCode, but a NULL value (this includes DataTypes other than String).
2) Servers can have Variable Nodes with a NULL DataValue, so it has no StatusCode (or timestamps, etc.).

Will the change to spec break existing Servers? What should the Client expect to get, and how should it interpret the return values?

Issue History

Date Modified Username Field Change
2024-01-29 23:00 Jeff Harding New Issue
2024-01-30 18:01 Jeff Harding Note Added: 0020736
2024-01-30 19:49 Jim Luth Note Added: 0020738
2024-01-30 20:24 Jim Luth Note Added: 0020739
2024-02-05 16:29 David Levine Note Added: 0020769
2024-02-05 16:30 David Levine Note Edited: 0020769
2024-02-05 16:31 David Levine Note Edited: 0020769
2024-02-06 16:46 Jim Luth Project 10000-008: Data Access => 10000-004: Services
2024-02-06 16:46 Jim Luth Assigned To => Matthias Damm
2024-02-06 16:46 Jim Luth Status new => assigned