Example of how use <optional>-dependency from a dependency used in your project. If a dependency in a project has a optional dependency defined,you has to define the optional dependency as a dependency in your project. But you has also to set the version for this dependency. In this example is the optional dependency of javassist/cglib (bytecode manipulation library) in hibernate-core used, to show how you specify this dependency without to define the version. The example show how we can reuse the version defined in the hibernate-parent artifact.