XBEL
The XML Bookmark Exchange Language (XBEL) has its origins in the Python community. It is described as an internet "bookmarks" interchange format and has similarities to the OPML format. I first encountered XBEL as the core format of the uPortal bookmarks channel. I have since used it as the main storage format in numerous web applications including a bookmark manager, newsfeed aggregator and several "shopping basket" types of program. As you can probably tell from my other blog entries I like to mix Java with XML technologies which probably partly explains my infatuation with this format.
Example XBEL tree:
tree.xml
DHTML Tree
I first discovered the DHTML tree widget on a page entitled Unobtrusive DHTML, and the power of unordered lists. This appealed to me as I am required to write accessible web applications and this looked a pretty neat solution without necessitating the need for JavaScript to be enabled in the browser. It also transfers a lot of the load associated with rendering tree refreshes from the server to the client side. The above DHTML tree was extended by Matt Kruse to add expand/contract functionality. I recently re-implemented the DHTML tree inspired by the mechanism of D.D. de Kerf's Easy DHTML TreeView but using unordered lists instead of table layout. The reason I moved to D.D. de Kerf's design was to allow multiple trees to exist simultaneously on a single page that would not interfere with each other but would share the same static CSS and JavaScript files (not perfect yet).