Method and system for selectively caching web elements

#The present invention relates generally to Internet/Intranet network systems, and in particular, to web caching where individual elements of a web page are selectively cached.

#Web caching is generally well known to those skilled in the art. Generally, a web cache sits between web servers (or remote servers) and a client and watches requests for HTML pages, images and files (known as objects) as they come by, saving a copy for itself. Typically, the web cache resides in a proxy server that sits in a local server. Then if there is another request for the same object, it will use the copy that it has, instead of asking the remote server for it again.

#There are two main reasons for using web caches. One is to reduce latency. Because the request is satisfied from the cache (which is closer to the client) instead of the remote server, it takes less time for the client to get the object and display it. This makes web sites seem more responsive. The second reason is to reduce traffic. Because each object is only gotten from the server once, it reduces the amount of bandwidth used by a client. This saves money if the client is paying based on traffic, and keeps their bandwidth requirements lower and more manageable.

#FIG. 1 illustrates an Internet/Intranet network system in which the present method of selective caching of web elements may be employed.

#FIG. 2 illustrates a table used by the current cache system to keep track of the URL, time of last access, and time stamp of web pages and the elements that make up the web pages.

#FIG. 1 illustrates a typical client/server Internet/Intranet network environment where the present method of selective caching of web elements may be employed. As illustrated, FIG. 1 shows a plurality of clients 10, 12, 14 connected to a local server 14. The local server 14 houses a proxy server 16 where caching is accomplished. The web cache is shared by all of the clients. The local server 14 is connected to Internet or Intranet 20 and can receive from a remote server 18 various documents or objects such as web pages, graphic files, audio files, etc. Although here the proxy server 16 was shown to be in the local server 14, it should be understood that it may be found in other devices such as a router or a gateway.

#In the present invention, a table as shown in FIG. 2 is created in the proxy server 16. As illustrated, this table keeps track of URLs of all web pages that are requested by any of the clients 10, 12, and 14. For each of the URLs listed, the table keeps the time the last client accessed the web page, and the corresponding modification time stamp of when the page was last modified. This modification time stamp, hereinafter referred to as simply the “time stamp”, refers to the last time something changed in the content at this particular URL. As an example, assuming that a client has requested the web page having the URL www.cnn.com, the table in FIG. 2 includes the URL “www.cnn.com” 30, the time 32 any client served by this cache last accessed the web page, and the page's own corresponding time stamp 34, indicating when anything on it was last modified. Assuming for this example that the web page having the URL “www.cnn.com” has three graphic files and an audio file, the URLs of each of the graphic files and audio file is also listed under the main web page as sub-entries. Here, the graphic files have the URL, “www.cnn.com/graphic.jpg1”, 36, “www.cnn.com/graphic.jpg2” 38, and “www.cnn.com/graphic.jpg1”, 40. The audio file has the URL, “www.cnn.com/audio” 42. For each of the URLs of the sub-entry URLs, the corresponding last-access time and time stamp are also listed.

#Of course, in reality, the table will contain multiple URLs and their corresponding sub-entries. How many URLs and sub-entries are allowed depends on the size of the cache and can vary from system to system. If the table is already full, then the most recently requested web page URL which is not already found in the table will be placed into the table, and the “oldest” web page URL will be removed from the table, based on the oldest “access” time entries in the table.