# Using Version Qualifiers

Eclipse bundles and features have version numbers of the form major.minor.micro.qualifier. The qualifier segment of the version is often used to indicated a specific build. If you set your feature or plug-in version qualifier to "`qualifier`" (ie a version of `1.0.0.qualifier`), then PDE build will automatically replace the word "qualifier" with a generated qualifier.

## Controlling the Generated Qualifier

The value of the generated qualifier is determined by the first of the following items that apply:

1. If the property `forceContextQualifier` is set in your build configuration build.properties file, then the value of this property is used as the qualifier. This property can also be set on the command line with -D when invoking ant.
2. If you are using map files to fetch your bundles from a repository, then the tag that was used to fetch the bundle will be used as the qualifier.
3. If neither forceContextQualifier nor map files are used, then the qualifier will be a time stamp in the form YYYYMMDDHHMM (ie 200605121600)

## Feature Version Suffixes

You can turn on the generation of qualifier suffixes for features by setting the property `generateFeatureVersionSuffix="true"` in the build configuration build.properties file.
The idea of a version is that it should increment each time something changes, the version qualifier increments and captures changes from build to build. Features rarely change, however, they do contain plug-ins which may change often. When version suffixes are turned on, a feature version will have the form major.minor.micro.qualifier-suffix. The suffix is in effect the sum of the version qualifiers of all the features and plug-ins included by the feature. This means that when one of the included plug-ins increments its version, then the version of the feature will automatically increment as well. This is particularly useful when the feature is deployed via an update site.