Provides model support for extending the base installation and update services.

## Package Specification

This package provides a convenience implementation of the default model objects and parsers used for writing pluggable support of alternate feature packaging schemes and update site access mechanisms. In general, most developers do not need to directly use the classes defined in this package. Instead, they can use the corresponding derived implementation classes contained in package org.eclipse.update.core.

Classes in this package would typically only be used directly when writing and alternate set of model objects for a feature and type implementation.