What is Problem diagrams ?

Problem diagrams

A context diagram can be further detailed by indicating explicitly which component controls a shared phenomenon, which component constitutes the machine we need to build, and which components are affected by which requirements. The resulting diagram is called a problem diagram (Jackson, 2001).

A problem diagram excerpt for the meeting scheduling system. A rectangle with a double vertical stripe represents the machine we need to build. A rectangle with a single stripe represents a component to be designed. An interface can be declared separately; the exclamation mark after a component name prefixing a declaration indicates that this component controls the phenomena in the declared set.

 For example

 The f label declaration  states that the Scheduler machine controls the phenomena determineDate and determineLocation. A dashed oval represents a requirement. It may be connected to a component through a dashed line, to indicate that the requirement refers to it, or by· a dashed arrow, to indicate that the requirement constrains it. Such connections may be labelled as well to indicate which corresponding phenomena are referenced or constrained by the requirement. 

For example

 The h label declaration  indicates that the requirement appearing there constrains the phenomena Date and Location controlled by the Scheduler machine.