A virtual application pattern is created using Virtual Application Builder, which allows you toto construct virtual application patterns using resources from its palette.
Plugins allow you to add custom resources to the palette. You can use them to build custom virtual application patterns, or extend existing patterns with function from your new plugins. Pattern types are licensed collections of plug-ins that are designed for a specific type of workload.
The IBM Workload Plugin Development Kit allows you to build custom plugins. InfoCenter pages describe how to install and manage plugins and pattern types in Workload Deployer.
Did I mention that the IBM Workload Plugin Development Kit is free? It was released on August 16, 2011, and is available now!
Get more information here in our wiki, including download links.