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Defining Virtual IOW Tags

Updated
  • Published on Jan 30, 2025
  • 1 minute(s) read
  • Denis Tkalec
  • Tomislav Renic
  • Elsa Tolsma

A Virtual Tag is a way of defining IOW Tags using dynamic expressions. Expression can be composed using PI Tags and built-in functions like:

  • +, -, *, /
  • MIN, MAX, MEAN, SUM, ABS, SQRT, STD
  • If then else
  • ( ) 

Creating Virtual Tags

To create a Virtual Tag:

  • First create a new IOW.
  • For the Variable select "Virtual Tag".
    Select the "Virtual Tag" Variable for your IOW.
  • Now the Expression field becomes available. You can either click the Edit button and define the Expression right away, or do this later after you have saved your IOW.
  • Remember to also fill in the other fields - refer to the IOW Record.

Opening the Expression

From the CL/System Details Page

To open the Expression from the CL Details Page (PEI Equipment) or System Details Page (PLSS Equipment):


  • Scroll to the IOW section.
  • Find your Virtual Tag (Variable = "Virtual Tag").
  • Click on the PI/Virtual Tag field.
Click in the PI/Virtual Tag field. 
  • Then click the Edit button the becomes available.
Click the Edit button.
  • Now you can define the Expression.

From the IOW Details Page

To open the Expression from the IOW Details Page:

  • In the Details section, click Edit.
  • In the Expression field click on the Edit button.

The Virtual Tag Expression can also be opened from the IOW Details Page.


Defining the  Expression

Below is an example where a Virtual Tag expression is defined and verified. You can select a PI Tag from the list and click the Add button to add the Tag to the expression. When done defining the expression, you can verify it by clicking the Test button.

Table Description automatically generatedA PI Tag is added to the expression with the Add button. The Test button is used to verify the expression.

When the Virtual Tag’s expression is verified, IMS will either show a green valid message or a red error message.

Table Description automatically generatedAn error message is shown in case of, e.g., a syntax error in the expression. 

You can learn more about the Formula Editor here.

PI Tags search using wildcards

When adding PI Tags to the IOW (also when adding it to a Virtual Tag expression), you can search for the Tag name using wildcards in the search string. Valid examples are:

  • *Test* (this is also default behavior when no wildcard is used)
  • Test*
  • *Test
  • Test
Graphical user interface, application Description automatically generatedSearching for a PI Tag using wildcards.