A message construct has the following form:

Each message statement consists of an identifier (the message name) and a string expression. Each message ends with a line break. The cost engine executes a message statement only when a rule with a matching name fails. See Rules for information on rules.

When the cost engine evaluates a message statement, it evaluates the string expression, and appends the result to the cost engine log. See String Expressions for information on string expression evaluation.

If a rule has more than one matching message, an error occurs when the module is saved.

See the following sections for information on each syntactic category mentioned above: