We use attributes to reference elements and attributes extensively to model context and relationships in our AF models. Is this going to be supported in the future? Kind regards, Gregor6 votes
This item is under review. Currently considering the following behavior for attributes links:
Error returned: “Unsupported data type: ‘OSIsoft.AF.Asset.AFAttribute’.”
Similar error for AFElement.
Change under consideration:
Value link for Attributes of value type “Attribute” returns the referenced attribute’s GET response (“/attributes/[webid]”)
Value link for Attributes of value type “Element” returns the referenced element’s GET response (“/elements/[webid]”)
The channel/websocket feature of PI Web API would be more useful if it was possible to subscribe/unsubscribe to attributes on an existing channel connection. Currently you have to open the connection with all the WebIds you want in the resource URL. If you want to change which values you are receiving, you would have to close the connection and open a new one. Adding this new feature would also solve issues with maximum URL length limitations.5 votes
This is an issue we definitely need to address for both the reasons you suggested. We should be able to add and remove attributes while a channel is open. We also need a mechanism for signing up for large numbers of WebIds when the list would be too long for a URL.
As a PI user, I want the OPC DA and HDA Servers to honor the Windows identity of any connected OPC client.3 votes
We understand the requirement. It makes sense. We have been looking into it but it turns out to be difficult to do. We used a third-party framework to build the PI OPC DA Server which separates interactions with the OPC client from interactions with the PI Data Archive. It solved a number of problems but unfortunately there is no easy way to have OPC client user credentials flow to the PI Data Archive. We are evaluating our options.
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