EclipseLink is the reference implementation of the Java Persistence Architecture (JPA) specification It also includes many enhancements and extensions.
For more information, see:
EclipseLink documentation center
http://www.eclipse.org/eclipselink/documentation/
The EclipseLink API reference documentation (Javadoc) for complete information on core JAXB plus the EclipseLink enhancements
http://www.eclipse.org/eclipselink/api/
Java Architecture for XML Binding (JAXB) specification
http://www.jcp.org/en/jsr/detail?id=222
Examples that display the use of a number of JAXB and EclipseLink MOXy features
http://wiki.eclipse.org/EclipseLink/Examples/MOXy
JAXB Tutorial
http://www.oracle.com/technetwork/articles/javase/index-140168.html