Entity Life History

An Entity Life History diagram is used to show the sequencing, iteration or timing of an entity. For example take a supporter of a charity for example. A supporter is an Entity within a charity and therefore real world events cans happen to this supporter such as change of address. Where as and Entity relationship Model (ERM) shows the link between supporters and cash, an Entity Life History diagram shows the events that take place on an entity such as a supporter.

 

Diagram 4.1

The above diagram shows the events of a Supporter. From the diagram one can easily see that a supporter record is created once a supporter makes a donation and can only be deleted after 7years have lapsed from the death of a supporter. This type of information can easily be missed out is other structured models. An ELH model should be created for each entity on the ERM. An asterisk * on the event box shows that this event may happen once, many times or may not happen at all.

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