Newbie question

[John]

Hi

i have been reading about XML and it says that one of the important features
of XML is the ability for deriving data from different databases that have
the same meaing but different formats.

I dont understand how it goes about doing this , is it related to the DTD,
infoset, XPath which allows data from different databases to be joined into
a common framework and then queried as a whole ?

I would be grateful if you can giive me basic information or point me to an
web address explaining this

thanks