Provisioning is the process by which data necessary for call completion is installed into the voice portal. Such data might include the subscriber identification, original calling party number, the called party number, and the transfer-to number. Any time phone numbers are involved in provisioning, the application designer should have at least a peripheral understanding of numbering plans. A numbering plan is the valid ranges of numbers that can be routed by the switches of a network service provider (CLEC, long-distance carrier, and so on). Any number falling outside this range will not be allowed to complete, usually resulting in a reorder tone.
The voice portal provider should provide the details of the allowable dialed numbers into the portal and the details of the dialing plan. Some providers even use a global 8xx number, where each service might have its own unique access code. For transferred calls leaving the portal, the application designer should ensure that logic exists to screen calls before the call is attempted. If the transfer number is to be provisioned by the subscriber through either a voice or web interface, the interface should do the screening. For subscriber-based services in general, the application designer must define the data schema and expected data flow to the voice portal provider. The voice portal provider can then use its position with the network provider to best meet the needs of the VoiceXML application.