This picture shows the interface for defining conditions. A condition can be an individual expression, an AND list of expressions, or an OR list of expressions. Here you can see the some of the conditions in the Meridian .pst file. For example, Class B is true when the database field “Class_ID” equals 4. A condition can be attached to any PatternStream target. And PatternStream publishes the target if and only if the condition is true.
     Parameter lists are used for defining arrays and variable-width table columns.