Both Supply-Side Platforms and Demand-Side Platforms
use Context Provider to retrieve data about Users,
Sites and Devices.
Supply-Side Platform and Demand-Side Platform need to independently decide
which instances of Context Provider they trust, and then independently query them.
Even in case Supply-Side Platform and Demand-Side Platform choose to trust
the same instance of Context Provider, they need to query it separately.
Context Provider needs to track Register Events. Thus,
Supply-Side Platforms and Demand-Side Platforms need to share with
Context Provider all the Register Events that they receive.
In response to a Register Event notification, Context Provider
returns a Context Script, and then receives the results of this script being executed
by a Supply-Side Agent within its sandbox.