Xml is not the only tool in the world that can be used to configure object wiring. It is sometimes more flexible and concise to wire up objects using a scripting language such as Ruby, Python or Groovy.

The NanoContainer (the sister project of Pico) is particularly strong on scripting language support.

Spring doesn't provide scripting language support. It is focused on xml configuration.

Yan has only xml configuration so far (in Nuts). But nothing prevents the scripting languages from being incorporated in.