The <rule> tag can take four attributes:

A rule must include either an op attribute or a src attribute. The op attribute specifies an operation to be performed on the child tags, which must be either <rule> or <valueof> tags. Rule tag operations define a relationship between properties, components, or other rules. The allowed operations are described below, in Rule Tag Operations.

The src attribute allows you to incorporate rules that have already been defined in another rule set. For more information about using the src attribute, see Including Rule Sets, Rules, and Sorting Directives

The name and tag attributes are optional; they are used by the Business Control Center and the ACC to label a rule and attach any client data to it.