The documentation for the existing 2006 implementation of XAML (Extensible Application Markup Language) has been published.
The XAML technical documentation set provides detailed preliminary technical specifications of Xaml Object Mapping. This documentation set includes details on Xaml’s data model for Types, Xaml’s data model for object hierarchies, and the techniques with which one maps from Xml to those object hierarchy data model. Also included is documentation of Windows Presentation Foundation’s (WPF) set of Types that can be used in conjunction with Xaml.
You can get the 548-page specification on the Extensible Application Markup Language (Xaml) spec download site.