I used XML, XSD and XSLT on an integration project between very dis-similar DB systems sometime in 2004. I had to learn XSD and XSLT from scratch but it wasn't hard. The great thing about these tools was that it enabled me to write data independent C++ code, relying on XSD and XSLT to validate/verify and then transform the XML documents. Change the data format, change the XSD and XSLT documents not the C++ code which employed the Xerces libraries.
For interest: the main XSD was 150KB and the average size of the XSLT was < 5KB IIRC.
The other great benefit is that the XSD is a specification document that the XSLT is based on. The two work in harmony. And specs are rare in software development these days.
Although I did not have too much trouble learning the declarative nature XSD and XSLT I did find that other C/C++ programmers had great trouble in adjusting to the declarative way. When they saw that was it, ah procedural they muttered, now that I understand! And they proceeded (pun?) to write procedural XSLT! The thing is you have to learn XPath and understand the axes of XML. Reminds me of old-time C programmers adjusting to employing OO when writing C++.
I used these tools as they enabled me to write a small C++ code base that was isolated from all but the most fundamental of data structure modifications and these latter were DB structure changes. Even though I prefer C++ to any other language I'll use what I consider to be useful to benefit the long term viability of a software project.
