The goal of the x-callback-url specification is to provide a standardized means for iOS developers to expose and document the methods they make available to other apps. Using x-callback-url’s source apps can launch other apps passing data and context information, and also provide parameters instructing the target app to return data and control back to the source app after executing an action. Specific supported actions will be dependent on the individual apps and will not be discussed in the specification.
Greg Pierce of Agile Tortoise, who is the developer behind Terminology, pinged me about this new spec. Previously, he exposed a protocol handler for Terminology, so that other apps could do word lookups using it. Clearly he’s built on that idea with x-callback-url and this standardization could prove to be very useful if the community adopts it.