Historically there has been several different mechanisms for associating metadata with a component. DNA attempts to learn from past mistakes and make the metadata format extensible to future needs and still simple to use. Thus runtime attribute access is the preferred method for accessing metadata about a component.
MetaClass is the toolkit used to access the metadata about any java class. The MetaClass metadata format maps to a simplified JavaDoc format and thus there is a very simple mapping between the DNA metadata model and MetaClass ClassDescriptor objects. See MetaClass documentation on how to access attributes at runtime.
MetaClass also supports generation of metadata descriptors from annotated Java source files. The annotations supported by DNA components are those specified in the model document.