Abstract:
A method for transmitting a web page to a client device is described. Template information, sub-template information, and delta information are identified based on a request for information from the client device. The template information includes seldom changing elements of a web page. The sub-template information includes: (i) information that changes less frequently than delta information, and (ii) elements of a web page shared by several templates. At least one of the template information, sub-template information, and delta information is retrieved from a location other than an originating server that is the original provider of information requested by the client device. The request is responded to by sending to the client device the template information, sub-template information and delta information. In addition, a system for transmitting a web page to a client device is described.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a Continuation Application of U.S. application Ser. No. 09/923,292, filed Aug. 6, 2001, entitled “Template Identification With Differential Caching” now issued as U.S. Pat. No. ______ on ______.  
         [0002]     This application is related to the following patent and copending applications:  
         [0003]     U.S. patent application Ser. No. 09/436,136, entitled “Predictive Pre-Download of Network Objects,” issued as U.S. Pat. No. 6,721,780 on Apr. 13, 2004;  
         [0004]     U.S. patent application Ser. No. 09/734,910, filed Dec. 11, 2000, entitled “Predictive Pre-Download Using Normalized Network Objects Identifiers”;  
         [0005]     U.S. patent application Ser. No. 09/827,268, filed Apr. 4, 2001, entitled “Server-Originated Differential Caching”;  
         [0006]     U.S. patent application Ser. No. 09/888,374, filed Jun. 22, 2001, entitled “Content Delivery Network Using Differential Caching”; and  
         [0007]     U.S. patent application Ser. No. 09/923,809, filed Aug. 7, 2001, entitled “Efficient and Low-Cost Compression Using Differential Caching”. Each of these applications is hereby incorporated by reference as if fully set forth herein. 
     
    
     FIELD OF THE INVENTION  
       [0008]     This invention relates to distinguishing different elements in a web page so as to reduce the bandwidth and computing resources required to transmit a web page over a network.  
       BACKGROUND OF THE INVENTION  
       [0009]     One technique to optimize bandwidth usage and save computing resources involves responding to a request for a web page by looking to what information a client device may have already received from a server at an earlier point in time. Information included in a document may be distinguished from other information included in that same document by looking to how frequently the information changes and whether a user has the most recent version of that part of the document. Using these criteria, information in a document may be categorized as either (1) template information (including information that changes infrequently) or (2) delta information (including information that changes relatively frequently or is somehow personalized with respect to a user). Differential caching and service of template and delta information results in a saving of bandwidth and other computing resources because information that does not change frequently may be compressed and cached at a server that is relatively proximate to one or more end users.  
         [0010]     Differential caching based upon the distinction between template information and delta information does not necessarily result in a substantial savings of bandwidth and computing resources under all conditions, particularly under those conditions when amount of delta information exceeds the amount of template information. For example, different elements in a personal web page, such as those provided by Yahoo, may change at very different rates with respect to each other.  
         [0011]     For example, the headline stories presented to a user may change every hour, whereas elements associated with the user&#39;s decision to view a particular topic may change only occasionally, and still other elements (such as the title bars in a page or logos associated with the provider of the content) may change very rarely. Under these circumstances, the template contains relatively little information compared to the amount of delta information. Under these circumstances, differential caching may not significantly reduce the amount of bandwidth and other resources needed to transmit a web page because a large part of the page must be freshly obtained from the content delivery network or re-compressed every time it is transmitted.  
         [0012]     Accordingly, it would be desirable to provide a technique for efficiently serving relatively non-static content in a content delivery network that does not suffer from the drawbacks of the known art.  
       SUMMARY OF THE INVENTION  
       [0013]     In a first aspect of the invention, information in a document is categorized with respect to the number of times that the information is served to a client or a set of clients within a period of time. The information in a document may be categorized as (1) delta information (that is, information that changes rapidly or is unique to a particular user), (2) sub-template information (including information that changes less frequently than delta information, and (3) template information, which changes very seldom. For example, a personalized web page (such as those available through Yahoo) may include (1) template information, such as the Yahoo logo and associated headers; (2) one or more sets of sub-template information, such as news reports, televisions listings and comparable information that change at more or less regular intervals, and (3) delta information, such as personal messages to an individual, stock market quotes or other relatively ephemeral messages.  
         [0014]     In a second aspect of the invention, both the template information and sub-template information are compressed and cached. Compressing and caching both sub-template information and template information results in a significant savings of bandwidth and computing resources, such as would be required if the sub-template information were treated as delta information and were not stored in a cache as is the case in the prior art. This savings is enhanced when the compressed template and sub-template information are sent to a large number of users.  
         [0015]     In a preferred embodiment, the sub-template and template information are treated separately, so that each is compressed and cached in a different location or a different memory address from the other. When a user requests a document, the document may be comprised of template, sub-template and delta information, some of which the requesting user or other users may have seen before. Selective compression and caching of these elements with respect to the likelihood that these elements will change can result in a savings of bandwidth and computing resources that is not available in the prior art.  
         [0016]     In a third aspect of the invention, the compressed and cached versions of the template and sub-template information are tagged with an indicator (referred to herein as an etag) that identifies the version number of a template or sub-template, so as to distinguish it from other, previous versions that a user may have received or that may be cached in a server, either in the content delivery network or on a proxy server. In a preferred embodiment, other types of electronic tags, such as place markers, are used to identify a location in the page where the material is to be inserted and provide other related information.  
         [0017]     In a fourth aspect of the invention, a hierarchy of templates and sub-templates is created, so as to form a lattice structure where a given sub-template can be shared by multiple templates. In a first example, a personalized web page associated with a user may include some of the same sub-templates as a different personalized web page associated with a different user. In this example, a template is associated with each user or group of users; this template references sub-templates which contain portions of the contents of the page (e.g. a sub-template for the weather section of the page, a sub-template for the news section, and so on). Such sub-templates can be shared by several templates (as occurs when several users wish to watch the same news). In a second example, sub-templates can be used in a personalized media stream as when a user watches a news story which includes personalized advertisement. If the number of different personalized advertisement streams is much lower than the number of individual viewers, it is most efficient to treat each advertisement stream as a sub-template, personalization information as delta information and the rest of the data stream as a template.  
         [0018]     In a preferred embodiment, differential caching of template and sub-template information and differential service of template, sub-template and delta information is particularly useful with respect to personalized web pages that are comprised of elements that can be configured in many different ways and sent to many different users. In other embodiments, this technique can be used with regard to database queries, streaming media and other information obtained from a network.  
         [0019]     In a preferred embodiment, an encoder specifies how the final page is to be assembled, but not where the assembly should occur. Thus, the web page can be assembled, either in whole or in part, by any downstream element that (1) understands encoding and (2) has access to the cached information. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is an overview of a system for new template identification with differential caching.  
         [0021]      FIG. 2  is an exemplary view of different elements in a web page that are differentially cached.  
         [0022]      FIG. 3  is a flow diagram, illustrating a method for using a system for new template identification with differential caching. 
     
    
     DETAILED DESCRIPTION  
       [0023]     The invention is described herein with regard to preferred steps and data structures. Those skilled in the art will recognize, after perusal of this application, that the described steps and data structures are not limited to any particular processing devices (whether general-purpose or special-purpose processing devices, or specific circuitry). Rather, those of ordinary skill in the art would be able to implement the described steps and data structures, and equivalents thereof, without undue experimentation or further invention. All such implementations are within the scope and spirit of the invention.  
       System Elements  
       [0024]      FIG. 1  is an overview of a system for new template identification with differential caching.  
         [0025]     A system for new template identification with differential caching (shown by general character reference  100 ) includes one or more clients  110 , an originating server  120 , a content delivery network  130 , a set of proxy encoder servers  140  and a communication network  150 .  
         [0026]     Each of the one or more clients  110  includes a client workstation  111  and a client operator  112 .  
         [0027]     The client workstation  111  includes a computing device, along with a local memory, operating system software and a display element. In a preferred embodiment, the computing device includes a personal computer, a hand held or laptop computer, a telephone interface (such as a cellular phone) to such a remote computer or any other device that fits the general Turing paradigm.  
         [0028]     The client workstation  111  also includes a web browser  113 . In some embodiments, the client workstation  111  also includes a decoder  114 .  
         [0029]     The web browser  113  (such as “Internet Explorer” , “Netscape Navigator” or a comparable product) uses a message transfer protocol, such as HTTP (hypertext transfer protocol), or a variant thereof, to generate request messages  115  and receive content (for example, web pages or information from a database) or other messages from the content delivery network  130 .  
         [0030]     The decoder  114  is either a browser add-on or is coupled to a proxy server locally close to the client  110  (for example, an enterprise or ISP cache).  
         [0031]     Regardless of location, the decoder  114  causes the web browser  113  to interact with the set of proxy encoder servers  140 , identifies previous versions of content that have already been received, decompresses compressed content and integrates the various elements comprising the content into a display for presentation to the client operator  112 . In a preferred embodiment, the decoder  114  is coupled to the web browser  113 , preferably as a browser add-on.  
         [0032]     Other embodiments (known as “clientless”) do not include a decoder  114 . In these clientless embodiments, the encoder encodes the templates and delta information at a level understandable by the browser  113  using DHTML, XML or some other scripting technique.  
         [0033]     The client operator  112  might include one or more individual persons or a proxy for one or more such persons (for example, a human administrative assistant, or a computer program or other artificial intelligence system acting on behalf of another).  
       The Originating Server and Content Delivery Network  
       [0034]     The originating server  120  includes a processor, computer program and data memory, and operates under control of software to perform the tasks described herein. It is capable of using a message transfer protocol, such as HTTP or a variant thereof, to receive request messages  115  for documents (for example, web pages) from clients  110 , the content delivery network  120  or the proxy encoding server  140  and to respond to those request messages  115 . In a preferred embodiment, the originating server  120  is the original provider of content.  
         [0035]     The content delivery network  130  includes a set of mirroring servers  135  situated in different locations throughout the network so as to minimize bandwidth required to respond to request messages  115 . Similar to the originating server  120 , the content delivery network  130  includes at least one processor, computer program and data memory, operates under control of software and is capable of using a message transfer protocol, such as HTTP or a variant thereof, to receive request messages  115  for documents.  
         [0036]     In a preferred embodiment, both the originating server  120  and the content delivery network  130  each include a database of documents such as web pages, embedded objects for web pages, databases or any information such as may be requested by a client operator  112 .  
         [0037]     In alternative embodiments, the content delivery network  130  may also include various databases for caching template information, sub-template information, delta information to be inserted into template or sub-template web pages, and code fragments or compressed versions of any of the above. In both preferred and alternative embodiments, the mirroring servers  135  include most or all of the same content as the originating server  120 , but are positioned more locally to the client device  110 . Information is served from the mirroring servers  135  to the client devices  110  so as to minimize bandwidth used to transmit content to a client device  110 . In this way, the mirroring servers  135  act as a unified content delivery network  130 .  
       Proxy Encoder Server  
       [0038]     Similar to originating servers  120  and mirroring servers  135 , the proxy encoder server  140  also includes a processor, computer program and data memory, and operates under control of software to perform the tasks described herein. The proxy encoder server  140  also includes compression software  142  and software  144  for identifying elements in a web page. Compression software  142  may include gzip or glib or some other comparable product that performs a compression algorithm such as Huffman coding or arithmetic coding. Software  144  for identifying elements in a web page can (1) distinguish, (2) isolate and (3) tag template information, sub-template information and delta information prior to compression, as well as (4) cache the compressed information.  
         [0039]     The proxy encoder server  140  is capable of using a message transfer protocol, such as HTTP or a variant thereof, to receive request messages  115  for documents (such as for example, web pages) from clients  110 , the content delivery network  130  or the originating server  120  and to respond to those request messages  115 .  
         [0040]     In a preferred embodiment, proxy encoder servers  140  are logically local to the originating server  120 . However, in other embodiments, they may be positioned between the client devices  110  and the content delivery network  130 . Requests from the client device  110  that are originally directed to the originating server  120  or the content delivery network  130  are redirected to the proxy encoder server  140 . In a preferred embodiment, the proxy encoder server  140  is transparent to the client device  110 , the originating server and the content delivery network  130 .  
       Communication Network  
       [0041]     Client devices  110 , the originating server  120 , the content delivery network  130  and the proxy encoder server  140  are coupled using a communication network  150 . In a preferred embodiment, the communication network  150  includes a computer communication network, such as the Internet. However, in alternative embodiments, the communication network  150  might include an intranet, extranet, VPN (virtual private network), ATM system, a portion of a private or public PSTN (public switched telephone network), a frame relay system, or any other communication technique capable of performing the functions described herein.  
       Content Distribution  
       [0042]     In a preferred embodiment, request messages  115  are generated by the client  110 . The request messages  115  are sent directly to the content delivery network  130  or the originating server  120 . If there is a proxy encoder  140  “in front” of either the content delivery network  130  or the originating server  120 , the request message  115  will be received by the proxy encoder  140 . The actions of the proxy encoder  140  are transparent to both the client  110  and the server. The proxy encoder server  140  retrieves the document, including template information and sub-template information (if such information is available) from the content delivery network  130 . If template and sub-template information are not available, software  144  is used to dissect web page and break it down into template information, sub-template information or delta information. Each of these components separately compressed, tagged with an etag to provide additional information and cached at the proxy encoder server  124 .  
         [0043]     In an alternative embodiment, each mirroring server  135  maintains a copy of template information and sub-template information for a particular document. When the document is requested by a client  110 , the mirroring server  135  provides the template information and sub-template information to the client  110  from its cache, while obtaining the delta information from the originating server  120  (or from a content distribution network  130  similarly disposed for distributing delta information). Sending the template information and sub-template information from the originating server  120  to the mirroring servers  135  is separate from sending the delta information from the originating server  120  to the client  110 .  
         [0044]     In a preferred embodiment, partial assembly of the template and sub-template information may occur at the mirroring server  135  or any other server that understands encoding and has access to the cached information. In this embodiment, the client  110  does not have to make multiple requests to the mirroring server  135  for different information. This is particularly beneficial to the client  110  who generally requires the total document, rather than the individual sub-templates.  
         [0045]      FIG. 2  is an exemplary view of different elements in a document that can be differentially cached.  
         [0046]     The document (indicated by general character reference  200 ) includes template information  210  (also referred to as a “template”), sub-template information  220  (also referred to as a “sub-template”) and delta information  230  (also referred to as a “delta”).  
         [0047]     Template information  210  (shown in the document  200  as a web page identifier) includes information that is relatively static and does not change frequently. For example, template information  210  may include logos associated with the site provider, title bars that identify the type of information that follows, a list of stocks in a user&#39;s portfolio for which the user frequently requests market quotes and other information that does not change frequently.  
         [0048]     In a preferred embodiment, the template information  210  is embedded with place markers  212 . Place markers  212  are used to define a location for the insertion of sub-template information  220  and delta information  230 .  
         [0049]     In a preferred embodiment, after the document  200  is requested by a client device  110 , the template information  210  is compressed and cached in an address associated with at least one location, such as the proxy encoder server  140  or a mirroring server  135 . An etag  214  identifies the version number of the template information  210 .  
         [0050]     Sub-template information  220  includes information that changes relatively frequently, such as a breaking news story, television listings that remain relatively constant for a day, an unchanging weather report and other comparable features. It is not uncommon for sub-template information  220  to be inserted in different locations in a web page during the course of a day. Similarly, different users may display identical sub-template information  220  in different places in their personal web pages. Under these conditions, the sub-template information  220  remains unchanged except for its location in a page. As noted above, place markers  212  are used to position such material in a document  200 .  
         [0051]     Similar to template information  210 , sub-template information  220  is compressed and cached at least one of a number of possible locations, including the mirroring server  135  and the proxy encoder server  140 . An etag  214  identifies the version number of the sub-template information  220 .  
         [0052]     Delta information  230  includes relatively ephemeral information such as stock quotes, personalized reminders to a client operator  112 , advertising content (such as banner ads), weather reports and similar matter that changes frequently.  
         [0053]     In a preferred embodiment, delta information  230  is not compressed or cached, but served directly to the client device  110  either by way of the proxy encoder  140  or directly from the content delivery network  130 . In other embodiments, the delta information  230  may be compressed and cached if it will be reused at a future point in time (such as rotating banner advertisements).  
         [0054]     Place markers  212  identify the location where delta information  230  may be inserted into the template information  210 . For-example, if template information  110  includes a list of stocks for which the client operator  112  requests quotes, the place marker  212  for the delta information (that is the individual stock quotes) will be embedded adjacent to the associated stock names.  
         [0055]     In another embodiment, the delta  230  includes code describing where and how to combine the sub-template(s)  220  with the template  210  to generate the document. Such embodiments do not require place markers  212  or  214 .  
       Method of Operation  
       [0056]      FIG. 3  is a flow diagram, illustrating a method for using a system for new template identification with differential caching.  
         [0057]     A method  300  includes a set of flow points and process steps as described herein.  
         [0058]     The method  300  is performed by the system  100 . Although the method  300  is described serially, the steps of the method  300  can be performed by separate elements in conjunction or parallel, whether asynchronously, in a pipelined manner, or otherwise. There is no particular requirement that the method.  300  be performed in the same order in which this description lists the steps, except where so indicated.  
         [0059]     At a flow point  310 , the system  100  is ready to begin performing a method  300 .  
         [0060]     At a step  311 , the client  110  generates a request message  115  for the document  200 . The request message  115  can be directed to either the mirroring server  135  or the originating server  120 . In a preferred embodiment, the request message  115  is made using the decoder  114 , preferably on the client&#39;s web browser  113 .  
         [0061]     In a step  312 , the decoder  114  sends the request message  115  to the proxy encoder  140 , situated preferably near the mirroring server  135  or the originating server  120 . Since the request message  115  was sent through the decoder  114 , the proxy encoder server  140  knows that the client can integrate template information  210 , sub-template information  220  and delta information  230  and is otherwise compatible with systems that provide delta encoding.  
         [0062]     In “clientless” versions (that is, those clients without a decoder  114 ) the request message  115  goes directly from the browser  113  to the proxy encoder server  140 , bypassing the decoder  114 .  
         [0063]     In a step  313 , the proxy encoder server  140  fetches a document  200  from either the originating server  120  or the mirroring server  135 , depending upon which is closest to the proxy encoder  140 . After obtaining this content, the proxy encoder  140  updates the template  210  for the document  200  and compresses the updated template  210 . In the event that there is not a template  210  associated with document  200 , the proxy encoder  140  generates a template  210 , compresses the template  210  and caches it.  
         [0064]     In a step  314 , the proxy encoder  140  determines whether sub-templates  220  are desirable and constructs the sub-template(s)  220 . This is done by looking to the size of the delta information  230 . If the delta  230  is very large with respect to the template  210  and includes regularized information, that regularized information is isolated and used as a sub-template  220 . As with the template information  210 , the proxy encoder  140  compresses and caches the sub-template information  220 .  
         [0065]     In “clientless” embodiments, the proxy encoder  140  responds directly with the delta information  230 . In such embodiments, the delta information  230  is an HTML page that includes a reference to template information  210 , one or more sets of sub-template information and delta information  230  (wherein the template  210 , the sub-template  220  are Javascripts and the delta information includes a set of Javascript instructions). In this embodiment, the Javascript instructions comprising the delta information  230  tell the browser  113  how to transform the template information  210  and sub-template information  220  into the correct HTML document. Other embodiments may use DHTML or other scripting techniques; still others may express the delta information as an XML page or a WML document.  
         [0066]     In a step  315 , the decoder  114  retrieves the compressed template  210  and the compressed sub-template  220  from either the proxy encoder server  140  or the mirroring server  135 , (depending where the proxy encoder  140  specified the compressed template  210  and compressed sub-template were cached in the previous step) by making a request, either immediately or at a later point in time. Upon retrieving the compressed template  210  and compressed sub-template information  220 , the decoder  114  decompresses them, and inserts the sub-template information as directly by the place markers  212 .  
         [0067]     In the clientless version, the browser  113  automatically and immediately retrieves the template  210  and the sub-template  220  from the site specified in the previous step.  
         [0068]     In a step  316 , the proxy encoder  140  sends the contents of the template  210  and sub-template  220 , and one or more etags  214  that correspond to the versions of the template  210  and the sub-template  220 .  
         [0069]     If the contents and etag  214  are sent from the mirroring server  135 , then the mirroring server  135  searches its cache for the template  210  and sub-template  220 . If the template  210  and sub-template  220  are present in its cache, the mirroring server  135  sends the template  210  and the sub-template  220  directly to the client  110 . However, if either or both of these elements are not present in the cache, then the mirroring server  135  automatically fetches the missing element from the encoder proxy  140 , caches the fetched element, and sends the element to the client  110 .  
         [0070]     The following steps occur when a client operator  112  (either the same client operator or a different one) subsequently requests the document  200 .  
         [0071]     In a step  317 , the client  110  requests a document  200  by generating a request message  115 . Similar to steps  310  and  311 , the decoder  114  directs the request to the proxy encoder  140 , changing as to further specify a version number that is used to ascertain if changes have occurred.  
         [0072]     In a step  318 , the proxy encoder  140  receives the request from the decoder  114 . If the proxy encoder  140  determines that a version of the template  210  or sub-template  220  are not present in the database, the proxy encoder  140  obtains the document  200  from either the originating server  120  or the mirroring server  135 , identifies template information  210  and sub-template information, compresses the template  210  and sub-template  220  and caches them.  
         [0073]     If, however, the template  210  and the sub-template  220  are available, the proxy encoder  140  calculates the differences between the versions of template  210  and sub-templates  220  that are available in the database and a newer version of the document  200  such as may be available from the originating server  120  or the mirroring server  135 . These differences may involve changes in the location where the sub-template is displayed (for example, two different users may choose to have the same information in a personal web page displayed in different locations). Such changes are not true delta information  230  because they can be remedied by positioning information that is already present in a cache differently in a document  200 . Other differences may be true delta information  230 .  
         [0074]     In a step  319 , the proxy encoder  140  may send either the delta information  230  to the decoder  114  (that is, if the decoder  114  can accept delta information  230 ) or it sends the document  200  to the client  110 .  
         [0075]     Steps  317  through  319  are described with respect to a client-server implementation. In the “clientless” version, the proxy encoder server  140  does not need to know which version of the template  210  and sub-template  220  are at the client  110 . This information is not needed because the proxy encoder server  140  makes this decision a priori and instructs the client  110  to use a specific version of these elements. Under these circumstances, steps  317 - 318  in the “clientless” version involve the browser  113  (rather than the decoder  114 ) directing the request message  115  to the proxy encoder  140 .  
       Alternative Embodiments  
       [0076]     Although preferred embodiments are disclosed herein, many variations are possible which remain within the concept, scope and spirit of the invention; these variations would be clear to those skilled in the art after perusal of this application.