...Complex user interface elements can be realized often in few lines of code. Agar is also extensible at the low-level. The low-level API is documented such that modular drivers can be written which enable Agar applications to work seamlessly under many platforms graphics systems without any change at the application level.
Schema validation with simple dom php classes, that will check the xsd file before the xml based forms will accept any submit. The ajax wrapper should work with widgets to show any validation error to the form user.