Editing Directory assistance (section)

===Directory assistance data sources===
The service of 411 queries is often outsourced to a [[call centre]] that specializes in that function. Historically, when a single carrier provided most of the telephony services for a region, the data used to satisfy the search could come exclusively from that carrier's subscriber rolls. Today, when the market is fragmented amongst many carriers, the data must be aggregated by a [[data aggregator]] specializing in directory listings. The data aggregator distributes the data to the 411 services either on a "live" basis, actually servicing each query, or by periodically transferring large swaths of listings to the call center's systems for local searching.

The data aggregator collects the data from the rolls of many telecommunication carriers. Some carriers, such as [[Vonage]], do not send their customer rolls to the aggregator.