What happen with [b]role[/b] keyword,
I found sample http://www.xylax.net/hibernate:

<set role="names" table="names">
<key column="id" type="string">
<generator class="uuid.hex"/> </key>
<element column="name" type="string"/>
</set>

<class name="Foo" table="foo">
...
<collection name="names" column="name_id" role="names"/>
</class>


But I can't find [b]role[/b] keyword in hibernate-mapping.dtd

role is now name - please read a more up-to date tutorial.

but what about [b]collection [/b] keyword

and I think 2 cases quite different:
1.when using role - collection definition not linked to parent class
2.when using name - we linked to parent class

Seriously, you are looking at ancient stuff.

Like....Hibernate 1.x.

Use an up-to-date guide.