Tag Expressions

A tag expression is a set of statements that are evaluated to return a tag value. The statements are evaluated in sequence until a value is returned after which no further statements are evaluated.

See the Tag Expression Example for a worked example of a tag expression.

Create a tag expression if you want to calculate the value of a tag from an expression that includes mathematical operations, the values of other tags, or the value of object attributes. Tag expressions are created with the Tag Expression Editor.

Tags that use a tag expression are highlighted in yellow.

Shared Expressions

In the past, some tags used Shared Expressions. That is, the same expression was used by different tags. Your database may still contain some of these shared expressions although you cannot create new shared expressions. You can recognise a tag with a shared expression because it will be highlighted in green on the tag table in the Data Sources module.