Tool or library for comparing xml files

If I understand your problem, you likely have an application that uses XML files as the data storage and the GUI abstracts the "technical" tag names into "user friendly" labels - again, I am assuming. So it would be a natural extension to view differences in a similar way. I am also assuming your application doesn't have a diff facility that follows the "abstraction" concept.

I did some searching and found one app (ExamXML) that seems to come close with highlighting features. I downloaded the eval version and tested your files against it:

http://www.programmedintheusa.com/images/stack547399.png

It does a pretty good job of highlighting the differences. It seems pretty interactive and pops up with how many differences. It looks like you can change the colors it uses, so maybe you can use grays and whites to de-emphasize the tags. It also seems to have a lot of options that you can pre-set for your users as well.

I want to note that you will be hard pressed to find an XML comparison tool that will not show the tag names, as the tags are what give the content context. If you take away context, it becomes difficult to understand the data being displayed. Anyhow, maybe this tool might be helpful. Have you also tried to show your users some of these tools and see what they are willing to tolerate, sometimes they may surprise you. Hope this helps!

SourceGear's DiffMerge is free for a single-user:

http://www.sourcegear.com/diffmerge/

I am very surprised nobody mentioned Microsoft's XML NotePad

It's free and it can create a pretty good comparison, telling which elements/attributes have changed, moved, been deleted, etc.:

(Sorry if the screenshots are a little wide).

You can also apply XLSes to the XML file and do various editing operations. Well worth a try.