Is it easier to teach XSLT or XQuery to an experienced SQL developer? My recent training experiences indicates that XQuery is easier to learn.
For the last six years I have been building metadata management systems using a diverse set of XML-centric technologies. These languages include XML Schemas, XSLT, Schematron, XHTML, XForms and most recently XQuery. And to be honest, I really do enjoy XQuery. My job as a consultant is to develop feature-rich and highly customizable metadata management systems for my customers and also transfer the skills needed to maintain and extend these systems to my customers though formal training classes as well as one-on-one mentorship.
I have found that it has been very difficult to teach XSLT to an average support person that is only doing occasional XSLT development. But teaching XQuery has been much easier for me to teach when you consider that most of my students have had some exposure to SQL. Looking back on my own learning process, I recall took me about five months of almost continuous study to really feel comfortable with XSLT. Most of this learning curve was because I had not done production XSLT development. But I picked up XQuery in just a few weeks. Perhaps this is because I was already familiar with SQL and XPath. But perhaps this is because XQuery is a little bit more approachable.
I want to note that this does not necessarily imply a poor design of XSLT or the merits of functional programming. After I did learn XSLT I became a real evangelist of its elegance and beauty. At first I was frustrated by not being able to change a “variable”. Later I realized that this restriction is what made XSLT beautiful, simple and elegant. These features keep the transforms free of side-effects. Once XSLT scripts are deployed I seldom found problems. I became enthralled by the fact that the simplicity of the language implied that XSLT custom-hardware could allow transforms to be orders of magnitudes faster than software-only solutions. XSLT may always have a place in CPU-intensive applications.
The difference in my learning time and those of my students reflects the state of our existing knowledge base: most of are already familiar with SQL. Anyone that knows SQL can take a crash course in XQuery designed specifically for SQL developers. Priscilla Walmsley’s excellent book on XQuery (O’Reilly 2007) includes a single chapter targeted at SQL developers making the transition to XQuery that I use in many of my classes. And 90% of the small support and maintenance tasks that many support and maintenance people need to perform do not require them to ever use the more complex functions and modules features of XQuery.
So with this in mind, I have moved most of my metadata registry tools away from XSLT and toward XQuery. This seems consistent with other metadata managers are doing today. There are several people now working on open source metadata management systems.
What about you? Do you have experience teaching both XSLT and XQuery to SQL developers? What is your experience on the learning times?