Schema Changes for New Features
Mac OS X Server introduces a number of new features, particularly in terms of collaborative tools. Tools that require information to be stored in user and group accounts (or other types of Open Directory records) require additional schema attributes.
As such, the Open Directory schema has been expanded to support such things as iCal Server and the new Directory application.
The additional elements are fairly transparent in many cases, but administrators who have extended the Open Directory schema in the past or those who use custom LDAP mappings for clients (both of which are often used when integrating Open Directory with directory services on other platforms) might need to review their mappings or extensions to ensure compatibility with these new features.