The current 9ML specification is version 1.0.
The corresponding XML schema is located at http://nineml.net/9ML/1.0/NineML_v1.0.xsd. However, note that schema only validates the model hierachy and basic types, i.e. not all the requirements described in the specification.
For full validation of 9ML models, please use the officially supported lib9ML Python package. Software written in Python, or with a Python interface, can also take advantage of the convenient lib9ML API in order to add support for 9ML.
For 9ML examples, please see the catalog (https://github.com/INCF/NineMLCatalog).