In addition to breaking logical JARs into different components for customization, maintenance releases, and original distribution, an effort has been made to break client JARs into appropriate modular components so that resources required by one applet are not automatically downloaded by all applets.

This effort has been balanced with a desire to prevent any resource from being downloaded more than once, that is, included in more than one FCS JAR. DSU and Customization JARs will indeed duplicate resources contained by corresponding FCS JARs to override them without requiring an FCS JAR rebuild. Indeed only in small, targeted cases is a resource downloaded in more than one FCS JAR.

In general, these efforts have led to the use of a dependency tree (more precisely, a unidirected graph) of logical JARs as described in the following section.