0006965: 5.2.5 differentiates between a zero length array and a null array. A definition of what an "empty array" means is missing

ID	Project	Category	View Status	Date Submitted	Last Update

0006965	Compliance Test Tool (CTT) Unified Architecture	Api Change	public	2021-05-27 14:44	2021-10-15 02:35

Reporter	Jim Luth	Assigned To	Alexander Allmendinger
Priority	normal	Severity	block	Reproducibility	always
Status	assigned	Resolution	open
Product Version	1.04

Summary	0006965: 5.2.5 differentiates between a zero length array and a null array. A definition of what an "empty array" means is missing
Description	In several places in the specification, the term "empty" is used in the context of arrays. E.g. In part 3 for the InputArguments and OutputArguments or part 9 for the ConditionId. empty can be a null array and empty can be an array with zero length For arrays there is no definition what it means for the mapping, when an array is empty. For other mappings, like for variants in 5.1.6 in part 6, it is clearly defined what "empty" means.
Additional Information	Several server implementations exist, including the OPC Foundation Quickstart Alarms & Conditions Server, that accept both a null array and an array of zero length, in the select clause for the SimpleAttributeOperand for the ConditionId. At least one OPC UA server implementation is known that accepts only an array of zero length and causes interoperability issues with OPC UA clients that use a null array in the SimpleAttributeOperand for the ConditionId.
Tags	No tags attached.

Files Affected

Randy Armstrong 2021-05-27 14:44 administrator ~0014428	Added text to 1.05 RC: 5.1.9 Null, Empty and Zero-Length Arrays The terms null, empty and zero-length are used to describe array values. A null array has no value. A zero-length or empty array is an array with 0 elements. Some DataEncodings will allow the distinction to be preserved on the wire, however, not all DevelopmentPlatforms will be able to preseve the distinction. For this reason, null, empty and zero length arrays are semantically the same for all DataEncodings. Decoders shall be able to handle all variations supported by the DataEncoding, however, decoders are not required to preserve the distinction. When testing for equality, applications shall treat null and empty arrays as equal. When a DevelopmentPlatform supports the distinction, writing and reading back an array value may result in null array becoming an empty array or vise versa.

Jim Luth 2021-05-27 14:44 administrator ~0014429	Agreed to changes edited in telecon. Also agreed no Errata necessary.

Paul Hunkar 2021-05-27 14:50 administrator ~0014430	need to identify which services this will apply to then will need to generate actual test cases.

Paul Hunkar 2021-05-27 14:53 administrator ~0014431	This issue needs to be applied back to all previous CTT version that are still being supported.

Date Modified	Username	Field	Change
2021-05-27 14:44	Jim Luth	New Issue
2021-05-27 14:44	Jim Luth	Issue generated from: 0006829
2021-05-27 14:44	Jim Luth	Note Added: 0014428
2021-05-27 14:44	Jim Luth	Note Added: 0014429
2021-05-27 14:44	Jim Luth	Relationship added	related to 0006829
2021-05-27 14:45	Jim Luth	Project	10000-006: Mappings => Compliance Test Tool (CTT) Unified Architecture
2021-05-27 14:45	Jim Luth	Category	Spec => Api Change
2021-05-27 14:50	Paul Hunkar	Note Added: 0014430
2021-05-27 14:51	Paul Hunkar	Assigned To	=> Paul Hunkar
2021-05-27 14:51	Paul Hunkar	Status	new => assigned
2021-05-27 14:53	Paul Hunkar	Note Added: 0014431
2021-10-15 02:35	Paul Hunkar	Assigned To	Paul Hunkar => Alexander Allmendinger