The XML stream, as we said before, is an abstraction, which makes the
source of data irrelevant. It's like the spigot you
have in the backyard, to which you can hook up a hose and water your
lawn. It doesn't matter where you plug it in, you
just want the water. There's nothing special about
the hose either. As long as it doesn't leak and it
reaches where you want to go, you don't care if
it's made of rubber or bark. Similarly, XML parsers
have become a commodity: something you can download, plug in, and see
it work as expected. Plugging it in easily, however, is the tricky
part.