Recommended WAI-ARIA implementation for navigation bar/menu

Question

We are in the process of implementing (i.e. adding) WAI-ARIA support to the main navigation menu of a web portal. Menu is the one shown here:

Answer 1

A possible implementation would be:

HTML structure:

Roles:

• role=”navigation” for outer wrapper
• role="menubar" for
  navigation bar container
  • role="menu" for second-level
    containers
    • role="presentation" for first- and second-level
    • menu items (they are not needed in the exposed accessible menubar structure)
    • role="menuitem" for first- and second-level menu items

    Properties:

    • aria-haspopup="true" for first-level menu items having a submenu
    • aria-labelledby="ID of previous menu item" for second-level
      containers

      States:

      • aria-selected="true" on currently visited first- or second-level item; aria-selected="false" on the other items. That is to enforce the concept “selected <==> current page”
      • aria-expanded="true/false" for second-level
        containers
        • aria-hidden="true/false" for second-level
          containers
          • aria-activedescendant="" for main
            navigation bar container. This is an alternative to working with tabindex
            • tabindex=0 on currently visited item; tabindex=-1 on the other items. That is in order to first focus on the current page when tabbing to the navigation bar. It is an alternative to working with aria-activedescendant

            Keyboard:

            • Tab: Move focus in/out of the menu from other points in the web application.
            • Shift+Tab: Move focus in/out of the menu from other points in the web application, in the reversed order.
            • Right arrow: Next navigation bar item
            • Left arrow: Previous navigation bar item
            • Enter: Activate currently focused item (i.e. navigate to corresponding URL)
            • Space: Activate currently focused item (i.e. navigate to corresponding URL)

            Aug/2014: aria-selected Vs menuitem

            In reply to @Joshua Muheim comment: now I can see from here, as well as from his reference, that aria-selected attribute is not allowed for menuitem role.
            As I read from this recent SO answer there are some solutions given the current state of things, and there is a new proposed attribute too.