A Warnier/Orr diagram is a style of diagram which is extremely useful for describing complex processes (e.g. computer programs, business processes, instructions) and objects (e.g. data structures, documents, parts explosions). Warnier/Orr diagrams are elegant, easy to understand and easy to create. When you interpret one of B-liner's diagrams as a Warnier/Orr diagram, you give a simple, yet formal meaning to the elements of the diagram. 

The following is a quick description of the main elements of a Warnier/Orr diagram.
 

Bracket:	A bracket encloses a level of decomposition in a diagram. It reveals what something "consists of" at the next level of detail.
Sequence:	The sequence of events is defined by the top-to-bottom order in a diagram. That is, an event occurs after everything above it in a diagram, but before anything below it.
OR:	You represent choice in a diagram by placing an "OR" operator between the items of a choice. The "OR" operator looks either like  or .
AND:	You represent concurrency in a diagram by placing an "AND" operator between the concurrent actions. The "AND" operator looks either like  or .
Repetition:	To show that an action repeats (loops), you simply put the number of repetitions of the action in parentheses below the action.

The diagram below illustrates the use of these constructs to describe a simple process. 

You could read the above diagram like this: 

"Welcoming a guest to your home (from 1 to many times) consists of greeting the guest and taking the guest's coat at the same time, then showing the guest in. Greeting a guest consists of saying "Good morning" if it's morning, or saying "Good afternoon" if it's afternoon, or saying "Good evening" if it's evening. Taking the guest's coat consists of helping the guest remove their coat, then hanging the coat up." 

As you can see, the diagram is much easier to understand than the description. 

 For Warnier/Orr basics click here.