Tobias Schlitt has written up a new post looking at the identity pattern (an Enterprise application design pattern) and an implementation of Identity Map in the eZ Components framework.

The pattern affects the data access layer of an application and helps to avoid inconsistencies in data objects of your application. [...] In this article I want to give you a rough overview on the pattern itself and show you how you can test and use the functionality of PersistentObject.

The identity map pattern allows you to store/fetch objects across execution instances to reduce the overhead of recreating those objects every time. Tobias shows off the PersistentObject component as an example of it in action. It can create an identity map and store values (like session information in their example) and even includes methods to grab related objects as defined by calls to addRelatedObject.