Viewing Business Rules as Business Process Steps
Business Rules can be classified as Business Process Steps.
Business Process Steps, then, are a subtype (a special kind) of Business Rule. A business rule describes what is, or should be, the case in a business. A business process step describes how a task or subtask is performed in the day-to-day running of the business.
An example of a business rule that is a process step is a rule that says that people who rent a car must first sign a contract.
An example of a business rule that is not a process step is a rule that says that salaries of employees in a specific function should not exceed a specific limits.
You can define a Business Rule and decide at a later time that it is in fact a Business Process Step, or the reverse.
For Business Rules, only the unique Rule ID and the Rule's Definition are mandatory.
For Business Process Steps, Name and Sequence Number are also mandatory.
The Name identifies the task or process step at hand, e.g. "Quote Price" or "Pay" or "Customer Registration". The Sequence Number allows you to indicate where (or when) a Business Process Step takes place in the sequence of sub steps that make up the larger business process. The Belongs To value of each sub step is set to the ID of this larger business process.
Business Process Steps can only belong to other Business Process Steps, i.e. not to Business Rules that are not themselves Process Steps.
A Business Process Step may have "sub steps", but it may also have child Business Rules that are not themselves Process Steps.