The following are notes from the XML 101 class at Adobe MAX 2007. I’m skipping over the extremely basic XML principles and covering the more interesting stuff.

When use XML nodes over attributes? Attributes are good for set, simple values. If you have complex values, multiples of a particular entry, or you want more extensibility, use nodes for XML.

The presenter demonstrated using DTDs over XML Schemas. The DTDs use a very specific grammar that is not even XML-ish. It’s kind of yesterday’s XML descriptor. Nowadays, better to use XML Schemas, which are actually XML defining XML. Both are ugly in my opinion, and XML Schemas are more verbose (as XML usually is), but you might as well go with the latest, most accepted convention, which is the XML Schema approach.

By using DTDs and XML Schemas, apps can be cognizant of the structure of your XML language. Even from a developer’s viewpoint, this can be useful when editing XML within an IDE.

The real fun part is formatting the XML with XSL (eXtensible Stylesheet Language). Supports loops, conditional logic, and other processing. Think of it as CSS on steroids, for XML. With XSL, you can transform XML to HTML, or PDF, or other fun stuff.

XPath is the heart of XSL processing. Allows you to traverse the XML document and find exactly what you’re looking for, whether it’s a particular node or looping over a group of items (xsl:for-each).

You CAN send the XML and XSL to the client and have the transformation be done client-side. All modern browsers include the XML/XSL engine. But generally it is wiser to do the transformation on the server side.

In my opinion, this approach lowers the value of XSL, because I can just as easily write some CF that will act on the XML. Yeah, I can write numerous XSLs for different presentations (text-only, XHTML, PDF, etc), but I’d have to do the effort of writing different XSL docs for that, when I could just as easily write different CF processors that accomplish the same thing. Unless you are working with a huge number of documents of varying types, XSL may not provide a large enough of an advantage for a language like CF that so easily manipulates XML.

The final step is grabbing XML with Ajax (such as Spry) that will populate document spaces (tables, divs, etc) with the XML data very easily as well. Again, this approach is similar to the CF approach, but with a more JavaScript-heavy slant.