UML to XML translation

[WideBoy]

Hi,

I've been asked to create an XML namespace from a UML model diagram of
a logical(hence, no PK FKs) relational database schema.

I've read a lot of stuff on the web on how one might do this given
class association cardinalities and so forth. But one of the many
things I'm absolutely stumped by is how to translate an association
between two classes when no cardinality is specified?

So my questions are as follows:
1. How do you represent the scenario described ebove in a W3C XML
schema, i.e. Class A associated to Class B but with no given
cardinalities on the association?

2. A colleague has suggested that I represent such a situation by
traversing the association in both directions, i.e. represent in XML
schema a Class A (as child of) Class B and vice-versa. But how can my
instance documents be appropriately validated by such a schema? and
more importantly how can one garauntee data-interchangeability of
instance documents based on such a schema?

Any ideas on the above would be much appreciated.

Many thanks,

Naran