What is an expression? An expression is a mathematical phrase which combines numbers, variables and operators to show the value of something.
Being introduced in AC22, expression-based properties can come in hand when we want to create custom property values, representing the result of equations using existing AC properties. With more simple words, I can use the walls height and length values divided with the volume of a brick that’s going to be used during construction, to calculate the number of bricks needed and show it as an element specific property (e.g. making it available for walls and columns that are using bricks as their Building Material).
What are properties (or as we sometimes call them metadata)? They could be descried as the non-visual data of an element such as fire rating, acoustic rating (or the amount of bricks to be used for it’s construction). The available properties depend on the element’s Classification.
Property labels can use expression-defined properties and considering the fact that an expression-defined property can have sequences, this will make it possible for one property label to be used on different element types, displaying element-type specific properties.
Check the examples for expression-defined properties for a better understanding of how to use them.