A rule expresses the business logic that defines conditions applied to source data. You can add expression rules to streaming mapping to cleanse, change, or validate data. Create expression rules in the Analyst tool.
You might want to use a rule in different circumstances. You can add a rule to cleanse one or more data columns.
Rules that you create in the Analyst tool appear as mapplets in the Developer tool. You can use a mapplet in a mapping or validate the mapplet as a rule.
In a streaming mapping, you can use the following functions in expression rules: