Exposing Semantic Zoom behavior
Semantic Zoom is a touch-optimized technique used by Windows Runtime apps for presenting and navigating large sets of related data or content within a single view (such as a photo album, app list, or address book). For more info, see Guidelines for Semantic Zoom.
If you create custom controls that support Semantic Zoom behavior, you should expose the behavior to accessibility frameworks and assistive technologies. You can do that by assigning the Microsoft-specific Accessible Rich Internet Applications (ARIA) role called "ms-semanticzoomcontainer" to the control. To learn more about ARIA roles, see The Roles Model on the W3C website.
The XAML SemanticZoom control provides built-in accessibility support for Microsoft UI Automation. It reports support for the ExpandCollapse pattern and dynamically changes the promoted Name value based on which view is displayed. You shouldn't have to do anything special to have your content within a SemanticZoom be accessible. You do have to consider whether you're exposing a visible control for expand or collapse, or relying on the standard gesture for semantic zoom. If you expose a control, make sure that control can be invoked and is textually identified (by Name or HelpText) as being the control that is used to expand and collapse the SemanticZoom views.