Java has added functionality to the Extensions packages in the versions listed below:
Enhancements to the extension mechanism in version 1.3 included an extended set of manifest attributes that can be used for checking vendor and versioning information of installed optional packages. If an applet requires an optional package that isn't installed, or that is installed but has the wrong version number or is not from the appropriate vendor, the Java Plug-in can download the needed extension from a specified URL. For more information, see Optional-Package Versioning.
