When designing the directory data, think not only of the data that is currently required but also how the directory (and organization) is going to change over time. Considering the future needs of the directory during the design process influences how the data in the directory are structured and distributed.
Look at these points:
What should be put in the directory today?
What immediate problem is solved by deploying a directory?
What are the immediate needs of the directory-enabled application being used?
What information is going to be added to the directory in the near future? For example, an enterprise might use an accounting package that does not currently support LDAP but will be LDAP-enabled in a few months. Identify the data used by LDAP-compatible applications, and plan for the migration of the data into the directory as the technology becomes available.
What information might be stored in the directory in the future? For example, a hosting company may have future customers with different data requirements than their current customers, such as needing to store images or media files. While this is the hardest answer to anticipate, doing so may pay off in unexpected ways. At a minimum, this kind of planning helps identify data sources that might not otherwise have been considered.