In many cases we would like to perform this operationin the background and update or change only a part of the page.
很多情况下，我们都想在后台执行此操作，只更新或改变页面的一部分内容。
2
In the portal environment, refreshing an entire page to deliver one functionality can be an expensive operationin terms of network resources and overall performance.
在门户环境中，为了使用某项功能而刷新整个页面需要占用大量网络资源并损害整体性能。
3
The VehicleInventory does this with the mark (expiry) operation, in which the expiry parameter is a timeout period in case the customer leaves the page without completing the reservation.