新しいサーバー・プッシュ型ウェブ・アプリの呼称comet
ajaxに似ているけれどもajaxでない、新しいサーバー・プッシュ型ウェブ・アプリをアレックス・ラッセルAlex Russellはcometと名付けた。cometは何かの略称というわけでは全くなく、gmailにおけるgtalkのインテグレーションやmeeboなどがcometに当たるという。
New services like Jot Live and Meebo are built with a style of data transmission that is neither traditional nor Ajax. Their brand of low-latency data transfer to the browser is unique, and it is becoming ever-more common. Lacking a better term, I’ve taken to calling this style of event-driven, server-push data streaming “Comet”. It doesn’t stand for anything, and I’m not sure that it should. There is much confusion about how these techniques work, and so using pre-existing definitions and names is as likely to get as much wrong as it would get right.
So what makes these apps special? What makes them different from other things that might at first glance appear similar? Fundamentally, they all use long-lived HTTP connections to reduce the latency with which messages are passed to the server. In essence, they do not poll the server occasionally. Instead the server has an open line of communication with which it can push data to the client.
