The window splitter design pattern is at:
http://w3c.github.io/aria-practices/#windowsplitter

This pattern is largely complete. However, there are changes to the separator role for ARIA 1.1 that need to be addressed.

Changes that need to be made for the window splitter pattern:

• More detailed description.
• Describe how to label and set control values.
• aria-expanded is no longer supported in aria 1.1.
• aria-valuemin, max, and now are required by aria 1.1.