This is strictly the model for Maven POM (Project Object Model) in org.apache.maven.model package, delegating content to Maven 4 API immutable model. All the effective model building logic from multiple POMs and building context is done in Maven Model Builder.
The following are generated from this model:
ToAPiV3() and ToApiV4() transformers, and v4 package for Merger and v4 Reader and Writers for the Xpp3 XML parser,