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09/04/2017
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Hi,
I have a question about ArrayDimensions attribute of Variable NodeClass.
In Spec Part 5 Information Model Chap5.3 mention that “If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions can either be set to null or the Attribute is missing. This behaviour is server-specific.
If the ValueRank specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions Attribute shall be specified in the table defining the Variable.” But in Spec Part 3 Address Space Model Chap 5.6.2 Table 13, it displays that attribute ArrayDimensions is optional.
My question is : if I add a node of Variable NodeClass and set the ValueRank to 1, does the ArrayDimensions attribute become mandatory and I have to specify the ArrayDimensions attribute when I add node?
Thanks.
05/30/2017
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This seems like an inconsistency in the specification.
Please add a mantis issue so the WG can review and publish a clarification.
https://opcfoundation-onlineap…..n_page.php
My initial response is that the array dimensions is always optional.
06/03/2016
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Hello,
I have found that the ArrayDimension attribute cannot be relied on to provide information about the actual size of an array even if ValueRank is > 0. Part 3 of the spec calls for it to contain the maximum supported length, not the actual current length.
Even if this is set to a specific value at one instant the spec does not prevent a server from changing it. The only reliable way I have found to determine what the current dimensions and length of each dimension is set to, is to read the entire array (read without using an NumericRange).
Thanks
David Levine
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