An [[Invantive Studio/Repository/Concepts/Attribute Rule|attribute rule]] that refuses invalid data is written as follows: - Open the table in the tree and select its folder "Attribute Rules". - Choose [[Invantive Studio/Ribbon/Add|"Add"]]. - Enter the "Code" of the rule, choose the "Event Category", such as `M` for insert and update, and choose `E` as "Action Category". - Write the condition the row must meet in "Constraint Specification", such as `:new.date_end is null or :new.date_end >= :new.date_start`. - Write the "User Message" as a resource code, with up to five message parameters. - Switch "Create" on and choose [[Invantive Studio/Ribbon/Save|"Save"]]. The rule takes effect after the next [[Invantive Studio/Repository/Concepts/Generation of the Business Layer|generation of the business layer]].