Dynamically Detecting and Resolving New Aliases in PI ProcessBook Displays

In the world of real-time process data visualization, PI ProcessBook remains a staple tool for engineers and operators relying on accurate and timely data representation. Occasionally, you may need your ProcessBook display to automatically adapt when a new PI Point alias is added to the current module context—eliminating the need for manual refreshes or disruptive polling mechanisms.

In this post, I’ll walk through best practices for detecting and resolving new aliases or tags in PI ProcessBook using the PI SDK and event-driven techniques.

The Challenge: Real-Time Tag Resolution

Imagine you add a new alias to a module in the PI Module Database (MDB) or Asset Framework (AF), and you want your ProcessBook display to immediately resolve and show data for that alias, without waiting for a manual refresh or a timer-based poll. Polling can be resource-intensive and introduce unwanted lag for users.

The Event-Driven Approach

The answer lies with PI SDK Event Pipes—a robust way to monitor the Module Database (MDB) for changes. Event Pipes allow you to respond to events such as "add," "remove," or "edit" on PI Modules (including changes to aliases) in near-real-time. Here’s how you can leverage this:

1. Declare an EventPipe on PIModuleDB: In your VBA (or VB6) environment, declare a PISDK.EventPipe object and assign it to Server.PIModuleDB.EventPipe. This sets up event monitoring on the module database.

2. Consume the Events: Use the EventPipe's Take or TakeAll methods to pull event objects as they occur. Each event object contains properties to help you identify which module or alias was changed.

3. Trigger Context Re-Resolution: Upon detecting an alias addition or edit event for the current module context, refresh the PI ProcessBook display's context so it resolves the new alias and fetches the newly available data.

Refreshing the Display Context Properly

A key nuance is ensuring the display context is correctly re-evaluated. In ProcessBook VBA, this involves iterating over the ContextHandlers (which manage context linkage for Aliases, Properties, and ModuleContext) and invoking their ContextUpdated method. Here’s an example:

Dim ch As ContextHandler
For Each ch In Application.ContextHandlers
    ch.ContextUpdated ThisDisplay
Next

Pro Tip: Always reference context handlers by name ("Alias", "Property", "ModuleContext") rather than index. This best practice ensures your code adapts gracefully if the set or order of context handlers differs across computers.

Application.ContextHandlers("Alias").ContextUpdated ThisDisplay
Application.ContextHandlers("Property").ContextUpdated ThisDisplay
Application.ContextHandlers("ModuleContext").ContextUpdated ThisDisplay

Troubleshooting Tips

• Using Application.Refresh alone typically does not force the display to resolve new aliases; explicit calls to ContextUpdated are needed.
• After invoking context updates, verify context data before and after the change to confirm successful alias resolution.
• When programming in VBA, remember the differences in method call syntax compared to VB.NET (avoiding extraneous parentheses can make or break your code!).

Additional Resources

• PI SDK Programming Reference (PISDK.CHM), installed with PI SDK or available from your OSIsoft support portal.
• PI Square Community Forums, a trove of practical examples and expert Q&A.

Conclusion

By harnessing PI SDK Event Pipes and programmatically refreshing ProcessBook's context handlers, you can achieve dynamic, event-driven updates when new aliases or tags emerge in your PI Asset Model. This not only improves user experience but also reduces unnecessary system load compared to polling solutions.

Have you built event-driven solutions in PI ProcessBook or migrated similar logic to PI Vision or other visualization tools? Share your tips in the comments below!