根据Feed和存储限制使用一系列决策。例如:
Connect to the Web site, and download the XML source of the feed. The Feed Download Engine downloads feeds and enclosures via HTTP or Secure Hypertext Transfer Protocol (HTTPS) protocols only.
Transform the feed source into the Windows RSS Platform native format, which is based on RSS 2.0 with additional namespace extensions. (The native format is essentially a superset of all supported formats.) To do this, the Windows RSS Platform requires Microsoft XML (MSXML) 3.0 SP5 or later.
Merge new feed items with existing feed items in the feed store.
Purge older items from the feed store when the predetermined maximum number of items have been received.
Optionally, schedule downloads of enclosures with Background Intelligent Transfer Service (BITS).
使用HTTP发挥到极致,以尽量减少带宽浪费:
要限制其对服务器的影响,饲料下载引擎实现HTTP条件GET与HTTP增量编码(RFC3229)合并万维网链接。此实现允许服务器传输最低限度的更改说明,而不是传输客户端上缓存的全新资源实例。该引擎还支持使用Microsoft Win32 Internet(WinInet)的HTTP gzip支持进行压缩。
成功的同步意味着Feed已成功下载,验证,转换为本机格式并合并到商店中。响应于HTTP条件GET(If-Modified-Since,If-None-Match,ETag等)的HTTP 304 Not Modified的服务器响应也构成成功。
,并定义标准去除:
The following properties directly affect the number of items that remain after a synchronization operation.
PubDate—used to determine the "age" of items. If PubDate is not set, LastDownloadTime is used. If the feed is a list, the order of items is predetermined and PubDate (if present) is ignored.
MaxItemCount—a per-feed setting that limits the number of archived items. The feed's ItemCount will never exceed the maximum, even if there are more items that could be downloaded from the feed.
ItemCountLimit—the upper limit of items for any one feed, normally defined as 2500. The value of MaxItemCount may not exceed this limit. Set MaxItemCount to ItemCountLimit to retain the highest possible number of items.
参考
这就是我想的,谢谢您的确认。 –