XML document editor

[stan]

Let me start off this by saying that I probably don't even know enough to
properly format the question.

I have some software, for industrial control systems that generates export
files in an XML format. I would like to be able to edit these files, such
that I can for example replicate many copies of the same thing, each with
slight changes that make it unique, In years past, this was done by
exporting to an ASCII "flat file".

I have been hearing about XML for a while, but not really paying attention.
Now is the time I need to learn about this, it appears.

So, is there such a thing as an XML file editor? What I think I mean by
this is an editor that can open these files, and understand the properties
that are defined in them, and allow me to manipulate these objects? Is this
something Open Office can do? Or is there a better/different way of doing
this?

-- 
One of the main causes of the fall of the roman empire was that, lacking
zero, they had no way to indicate successful termination of their C
programs.