XSL[T|-FO]

My friend (and co-worker, and constant source of distraction) Kirt was poking around the company intranet today and came across a document detailing interview questions for “XSLT Developers”. When I was doing Java for a living I used XSLT quite a lot and eventually became quite good at using it effectively. Naturally, I was curious to see what we had to say about the qualifications of a good XSLT developer, especially since as far as I know, we don’t now, nor have we ever, used the slightest bit of XSLT for any part of our entire system.

Using the document to conduct an actual interview would have made for a pretty miserable experience which - since we’ve never used it and are unlikely to ever use it - I’m okay with. But it reminded me that there is a lot of confusion about what XSLT is and isn’t. XSLT and XSL are not synonymous. XSLT is a language for transforming XML documents. XSLT is but one of two components of the larger XSL, the other being XSL-FO: which is a language for specifying visual display. XSL is just a unifying term, a shorthard for saying “XSLT plus XSL-FO.” Wikipedia’s article on XSL disagrees with at least two points here but I won’t go into it other than to say that Wikipedia (though I love it so) is wrong.

I think that part of the reason why XSL and XSLT are used interchangeably is that in the beginning, XSLT pretty much was all of XSL. Sure, XSL-FO was envisioned early on but it took a long time to get a standard and it took a really long time to get an implementation. XSLT had a standard and multiple implementations while XSL-FO was nothing more than a dim idea. If you started using XSLT back then, you could be forgiven for thinking that was all there was to XSL.

The other point of confusion about XSLT is that it’s nothing more than a glorified variable substitution engine with horrid syntax. It’s syntax is retched and you certainly can use it to simply plug variables into an output template but XSLT is a lot more capable than that. It took me a long time to see and even longer to really understand that XSLT is basically a functional programming language.