I

Idempotent

A Latin word meaning that a method effectively acts only once when invoked one or more times. This is sometimes called a one-shot, since after the method acts, something must occur to rearm the method to act again. A simple case is a method that always sets a Boolean variable to true. Although the method always assigns true to the variable, effectively the method does nothing unless the variable is false. A more complex example is a Web application's servlet that processes the contents of the shopping cart when the user clicks the order button at the check-out page. Even if the user clicks the order button two or more times, the method in the servlet that handles the click is idempotent if it processes the contents of the user's shopping cart only once and generates the same response for each redundant click.

Identity string

The string obtained from the toString method of the durable JDO identity object.

Identity value

The value of an attribute, or a list of attributes, that uniquely identifies an object's persistent state in the datastore.