Flink和Storm之间的主要区别是什么？(What is/are the main difference(s) between Flink and Storm?)

 不，您只能通过访问页面，无法知道页面何时上次更新或上次更改或上传到服务器（可能取决于解释，可能是三个不同的东西）。 
 
 服务器可能（并根据HTTP 1.1协议）发送Last-Modified头 ，您可以通过几种方式找到，例如使用Rex Swain的HTTP查看器 。 但是，根据协议，这只是原始服务器认为该变体最后一次修改的日期和时间。 该协议实际上增加了：“该头域的确切含义取决于源服务器的实现和原始资源的性质。 对于文件，可能只是文件系统上次修改的时间。 对于具有动态包含零件的实体，它可能是其组件部件的最后一次修改时间集。 对于数据库网关，它可能是记录的最后更新时间戳。 对于虚拟对象，可能是内部状态最后一次改变。“ 
 
 实际上，网页通常是从内容管理系统或其他方式动态创建的，在这种情况下， Last-Modified标头通常会显示创建响应的数据戳，通常非常接近请求时间。 这意味着在这种情况下，标题几乎是无用的。 
 
 即使在“静态”页面（服务器简单地选择与该请求匹配的文件并将其发送）的情况下， Last-Modified日期戳通常仅表示对服务器上文件的最后一次写入访问。 这可能与文件从备份副本恢复的时间，或文件在服务器上编辑而不对内容进行任何更改的时间，或上传到服务器上的时间有关，可能会替换旧的相同的副本。 在这些情况下，假设时间戳在技术上是正确的，它表示页面未被更改的时间（但不一定是最后一次更改的时间）。 

No, you cannot know when a page was last updated or last changed or uploaded to a server (which might, depending on interpretation, be three different things) just by accessing the page.
 
A server may, and should (according to the HTTP 1.1 protocol), send a Last-Modified header, which you can find out in several ways, e.g. using Rex Swain’s HTTP Viewer. However, according to the protocol, this is just “the date and time at which the origin server believes the variant was last modified”. And the protocol realistically adds: “The exact meaning of this header field depends on the implementation of the origin server and the nature of the original resource. For files, it may be just the file system last-modified time. For entities with dynamically included parts, it may be the most recent of the set of last-modify times for its component parts. For database gateways, it may be the last-update time stamp of the record. For virtual objects, it may be the last time the internal state changed.”
 
In practice, web pages are very often dynamically created from a Content Management System or otherwise, and in such cases, the Last-Modified header typically shows a data stamp of creating the response, which is normally very close to the time of the request. This means that the header is practically useless in such cases.
 
Even in the case of a “static” page (the server simply picks up a file matching the request and sends it), the Last-Modified date stamp normally indicates just the last write access to the file on the server. This might relate to a time when the file was restored from a backup copy, or a time when the file was edited on the server without making any change to the content, or a time when it was uploaded onto the server, possibly replacing an older identical copy. In these cases, assuming that the time stamp is technically correct, it indicates a time after which the page has not been changed (but not necessarily the time of last change).