Software Design Center

Entity
Use a simple rectangle to represent an entity. This entity box will be the starting point for your ELH diagram.
Learn how to add and edit text on an entity.

Event
An event creates, modifies, or deletes an occurance of one or more entity types. The first event should be placed to the left, and at the same height, as the events that are expected to follow it.

Selection
To represent a choice between a number of alternative events, mark the events with a small "o" (for option) on the upper right hand corner.

Iteration
If an event is repeated, place a small asterisk (*) in its upper right hand corner. All events under a single node must be of the same type. In other words, don't mix and match iteration, selection, and sequence event notations.

Parallel Structures
To illustrate an event that has no major effect on the system, such as a change of an address for an employee, use a parallel bar to note this exception to the system's normal life.

Quit and Resume
To represent an unusual event (i.e. an employee taking family medical leave), you can use pairs of "quit and resume" events. Each event marked with a "Q", can be replaced by an event marked with an "R."

Quit and Resume
Place state indicators (SIs) under each event to indicate the states that precede and follow it. Use a slash to divide the states before and after the event takes place.