Implmeneting MongoDB style document references in XML databases

Implmeneting MongoDB style document references in XML databases

I'm a newcomer to XML databases and in particular, I am trying to learn
how Marklogic works. My apologies if these questions are too naive or
obvious.
What I'd like to do is to implement MongoDB style document references in
Marklogic since I think the pattern would apply wery well on the latter,
being itself a document oriented database.
This is what the MongoDB documentation has to say about manual and DBRef
style document references:
http://docs.mongodb.org/manual/reference/database-references/
MongoDB recommends the use of manual document references.
Now, the most direct approach I can see is to define this piece of
information as, say, a part of a schema definition; starting with the
definition of an objectid, a book and a publisher:
<xs:simpleType name="objectId">
<xs:restriction base="xs:string">
<xs:length value="24"/>
<xs:whiteSpace value="collapse"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="Publisher">
<xs:complexType>
<xs:attribute name="id" type="fbc:objectId" use="required"/>
<xs:attribute name="name" type="xs:string" use="required"/>
<xs:attribute name="location" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
<xs:element name="Book">
<xs:complexType>
<xs:attribute name="Title" type="xs:string"/>
<xs:attribute name="publisherId" type="fbc:objectId" use="required"/>
</xs:complexType>
</xs:element>
So three questions:
Would this suffice to model the document reference between a book and its
publisher? Is there a better approach for Schema based XML documents?
Would this approach introduce difficulties when doing XQueries inside
Marklogic (or any other XML database such as existDB, Senda or Basex?
Marklogic states that it can use "Modular documents" which hold some type
of special document references using XPointer and XInclude:
http://docs.marklogic.com/guide/app-dev/mod-docs
Are there any advantages in using that approach instead of manual document
references? Are there any working Java API examples this feature?
I apologize in advance if these are too many questions but I believe
they're all related to the overall question stated here. Thanks.