WebIQ groups items with the same subscription interval into a single subscription to the OPC-UA server. You have to define the subscription interval per item: https://www.smart-hmi.com/user/download/deliver/docs/documentation-manual-webiq-designer-2.15-ee64/i...
Your second question is not quite complete as you have to consider that the same HMI can be open in multiple devices at once.
WebIQ behaves very smart with this:
- an item is only subscribed with the OPC-UA server when it is currently subscribed by at least one widget/LocalScript in the HMI
- an item will be unsubscribed when the widget is no longer used, i.e. on a different view of a screen for example
- this is valid for all HMIs display open at once, i.e. if a single HMI display has a specific item subscribed it will be subscribed with the OPC-UA server
- however, if multiple HMI displays use that item there will only be once single subscription to the OPC-UA server
In general, WebIQ uses the most efficient OPC-UA subscription model: only subscribe items when they are actually used in at least one HMI display currently.
Please note that however - when it comes to the maximum number of item subscriptions - you have to take into the account the maximum number of concurrent displays of the HMI you expect because one HMI display can be on screen 1, another on screen 2 and another on screen 3 - if now all of these screens have 10 different items you have 30 item subscription. If all screens have the same 10 items you only have 10 item subscription.
