If your database contains Group Templates, you can use Template expressions to define how properties in the Group Instances derive their values from the Group Template. You do this by defining expressions in the Property Overrides window (see Use Template Expressions to Configure Property Values in the ClearSCADA Guide to Core Configuration).
Template expressions support a subset of the grammar of Standard Expressions . You do not include tags in Template expressions; instead, you use Template parameters (see Template Parameters).
You can only apply Template expressions to 'simple' values, such as strings, numeric and ordinal values, database references, and Area of Interest references. The Property Overrides window only provides a 'By Expression' option next to those properties for which you can apply an expression.
ClearSCADA recalculates a Template expression in the following circumstances:
- On creation
- When the Template expression is modified
- When the value of a parameter in the Template expression changes
- When a Group Instance is configured to reference the Group Template to which the Template expression applies
- When the name of a Group Instance is changed (and that Group Instance references the Group Template to which the Template expression applies)
- When a Group Instance is moved (and that Group Instance references or referenced the Group Template to which the Template expression applies).
Further Information
Configuring Group Templates and Group Instances: see Group Templates and Group Instances in the ClearSCADA Guide to Core Configuration
Configure Template Expressions and Template parameters in a Group Template: see Define which Property Values Derive from a Group Template in the ClearSCADA Guide to Core Configuration.
Set the Template parameter values in a Group Instance: see Configure the Properties that are Unique to the Items in a Group Instance in the ClearSCADA Guide to Core Configuration.