Stop learning proprietary languages and memorizing template tags. Symphony leverages open standards like XML and XSLT, and good old XHTML and CSS. Even the admin interface employs the widely-used jQuery library, so extension developers don’t have to learn a whole new framework when extending the back end.
XCONCUR is an experimental markup language with the major goal to provide a convenient method to express concurrent hierarchies in an XML-like fashion. XCONCUR-CL is a validation component in XCONCUR and allows cross-layer validation.
adgerFish is a convention for translating an XML document into a JSON object. Once you've got your XML document represented as a JSON object, it's easy to manipulate from within Javascript. If you're familiar with PHP's SimpleXML extension, think of BadgerFish as aiming for a similar goal: making it simpler to do common manipulations of XML documents with a predictable structure.