A fragment is used to replace or extend the functionality of an existing plug-in. A common use for fragments is to put environment (operating system, architecture, etc.) specific code into fragments. Depending on the environment the plug-in is installed in the base plug-in code along with the correct fragment can be installed. Fragments are also ideal for shipping features like language or maintenance packs that typically trail the initial products for a few months.

When a fragment is detected by the platform and its parent plug-in is found, the fragment's libraries, extensions and extension points are "merged" with those of the parent plug-in.

While this merging mechanism is good from a runtime point of view, developers need to view fragments as separate entities while working on them.

PDE provides full support for fragment development. Fragments can be viewed as "limited plug-ins". They have all of the capability of regular plug-ins but have no concept of life-cycle. Fragments have no top-level class with "startup" and "shutdown" methods.

To create a fragment use the New Fragment Project wizard. Editing fragments is very similar to editing plug-ins.

Plug-in Editor
New Fragment Plug-in