JPAs specification concentrates on specifying persistence of classes using Java5 annotations, but you can also specify the persistence using metadata. You can define the MetaData in files of any name but the default is "orm.xml", stored under /META-INF MetaData mapping files for JPA have to match the format defined by the XSD for that file

Here is an example valid for orm.xml files with XSD specification

<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm
        http://java.sun.com/xml/ns/persistence/orm_1_0.xsd" version="1.0">
    ...
</persistence>

Your MetaData should match the XSD specification.