No explicit Synthetic Spread behavior is defined. Reading Systems may use Synthetic Spreads in specific or all device orientations
Reading Systems should render a Synthetic Spread regardless of device orientation.
Reading Systems should render a Synthetic Spread for spine items only when the device is in landscape orientation.
Reading Systems must not incorporate spine items in a Synthetic Spread.
Describes in which orientations the reading system should present the publication in spread mode. Can be overridden per content document.