With some clever manipulation you can create a relational system
Wes, don't confuse the poor lad even more. There is absolutely no manipulation adding a data relation to XML file, there is only adding the DataRelation. It is exactly the same for any connection based DBM. The biggest difference is that with XML it will write the DataRelation to the XML, thus you need not try to add it again. This is why in my example it first checks for relations prior to adding them.

I think you should first ask him/her what the application of the dataset is prior to suggesting a DBM. There are plenty of applications why a simple XML based dataset is spot-on