Method and apparatus for redirection of server external hyper-link references

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to the control of network information server systems supporting World Wide Web based data pages and, in particular, to a server system and process for efficiently redirecting external server hyper-link references for purposes of controlling, moderating, and accounting for such references.

2. Description of the Related Art

The recent substantial growth and use of the internationally connected network generally known as the Internet has largely been due to widespread support of the hypertext transfer protocol (HTTP). This protocol permits client systems connected through Internet Service Providers (ISPs) to access independent and geographically scattered server systems also connected to the Internet. Client side browsers, such as Netscape Mozilla.RTM. and Navigator.RTM. (Netscape Communications Corp.), Microsoft Internet Explorer.RTM. and NCSA Mosaic.TM., provide efficient graphical user interface based client applications that implement the client side portion of the HTTP protocol.

Server side application programs, generically referred to as HTTPd servers, implement the server side portion of the HTTP protocol. HTTP server applications are available both commercially, from companies such as Netscape, and as copyrighted freeware available in source code form from NCSA.

The distributed system of communication and information transfer made possible by the HTTP protocol is commonly known as the World Wide Web (WWW or W3) or as simply "the Web." From a client side user interface perspective, a system of uniform resource locators (URLs) is used to direct the operation of a web browser in establishing atomic transactional communication sessions with designated web server computer systems. In general, each URL is of the basic form:

http://<server_name>.<sub-domain.top_level-domain>/<path>

The server_name is typically "www" and the sub_domain.top-level_domain is a standard Internet domain reference. The path is an optional additional URL qualifier.

Specification by user selection of a URL on the client side results in a transaction being established in which the client sends the server an HTTP message referencing a default or explicitly named data file constructed in accordance with the hypertext mark up language (HTML). This data file or web page is returned in one or more response phase HTTP messages by the server, generally for display by the client browser. Additional embedded image references may be identified in the returned web page resulting in the client browser initiating subsequent HTML transactions to retrieve typically embedded graphics files. A fully reconstructed web page image is then presented by the browser through the browser's graphical user interface.

Due to the completely distributed client/server architecture of the Web, as made possible by the URL system further supported by the existing Internet name resolution services and routing conventions, HTTP servers can be independently established with little difficulty. Consequently, the Web has no centrally or even regionally enforced organization other than loosely by name of the top level domain. Searching for information or other resources provided by individual HTTP servers is therefore problematic almost by definition. Because of the time, cost and complexity of assembling comprehensive, yet efficiently searchable databases of web information and resources, commercial Internet Business Services (IBS) have been established to provide typically fee based or advertising revenue supported search engine services that operate against compilations of the information and resources available via the Web correlated to source URLs. Access to such search engines is usually provided through server local web pages served by the Internet Business Services. The results of a search are served in the form of local web pages with appropriate embedded remote or hyper-linked URLs dynamically constructed by the server of the Internet Business Service.

Because of the opportunity presented by the likely repeated client access and retrieval of search engine and search result web pages, providers of other Internet based services have begun to actively place advertisements on these web pages. As is typical in advertising mediums, the frequency of display of an advertisement generally defines the compensation paid to the advertisement publisher. Thus, the number of times that an advertisement is simply transferred to a client browser provides an indication of how effectively the advertisement is being published. A more direct measure of the effectiveness of a particular advertisement on a particular web page is the number of times a client web browser chooses to actively pursue the URL represented by the advertisement. Thus, there is a need to be able to track information obtainable from a client browser when a hyper-linked advertiser's URL is selected.

The difficulty in obtaining direct reference information arises from the fact that a web page with an embedded advertisement and corresponding remote URL is served in its entirety to the client browser upon first reference to the web page. The selection of a particular advertiser's URL is then by definition performed through an independent transaction directed to the HTTPd server associated with the advertiser. Since the advertiser publishing HTTPd server is not part of this subsequent transaction, the publishing server is conventionally incapable of tracking client browser hyper-links actually executed to an advertiser's URL or any other URLs embedded in a web page previously served to the client browser.

Simple web page access counters are relatively well known and used throughout the Web. These access counters are based on a common gateway interface (CGI) facility supported by modern HTTPd server systems. The CGI facility permits generally small programs, at least typically in terms of function, to be executed by a server in response to a client URL request. That is, the HTML web page definition provides for the embedding of a specific HTML reference that will specify execution of a server side CGI program as part of the process of the web browser reconstructing an image of a served web page. Such a HTML reference is typically of the form:

<img src="http://www.target.com/cgi-bin/count.cgi">

Thus, a counter value incremented with each discrete execution of the CGI program (count.cgi) dynamically provides part of the displayable image of the reconstructed web page. The time, remote client requester, client domain, client browser type and other information that may be known through the operation of the HTTP protocol may be logged as part of the CGI program's function. Consequently, a reasonable manner of accounting and auditing for certain web page accesses exists.

Access counters, however, fundamentally log only server local web page accesses. The client browser to the CGI program is evaluated by the client in connection with the initial serving of the web page to the client browser. The initial serving of the web page to the client browser can be connected, but any subsequent selection of a URL that provides a hyper-link reference to an external server is not observed and therefore is not counted by a CGI program based access counter. Other limitations of access counters arise from the fact that the implementing CGI program is an independently loadable executable. The CGI program must be discretely loaded and executed by the server computer system in response to each URL reference to the CGI program. The repeated program loading and execution overhead, though potentially small for each individual invocation of the CGI program, can represent a significant if not substantial load to the sever computer system. The frequent execution of CGI programs is commonly associated with a degradation of the effective average access time of the HTTPd server in responding to client URL requests. Since an Internet Business Service providing access to a search engine logs millions of requests each day, even small reductions in the efficiency of serving web pages can seriously degrade the cost efficiency of the Internet Business Service. As of December, 1995, Infoseek Corporation, in particular, handles an average of five million retrievals a day.

The execution overhead associated with CGI programs is often rather significant. Many CGI programs are implemented at least in part through the use of an interpreted language such as Perl or TCL. Consequently, a substantial processing overhead is involved in multiple mass storage transfers to load both the interpreter and CGI program scripts, to process the scripts through the execution of the interpreter, and then actually log whatever useful data is generated, typically to persistent mass storage. Finally, the interpreter and/or CGI program may have to be unloaded.

In addition, external CGI programs present a significant problem in terms of maintenance, including initial and ongoing server configuration and control, and security in the context of a busy server system. Individual CGI programs will likely be needed for each independent web page in order to separately identify web page service counts. Alternatively, a CGI program can be made sufficiently complex to be able to distinguish the precise manner in which the program is called so as to identify a particular web page and log an appropriately distinctive access count. Maintenance of such CGI programs on a server system where large numbers of page accesses are being separately counted is non trivial.

Further, the existence of external programs, particularly of scripts that are interpreted dynamically, represents a potential security problem. In particular, the access and execute permissions of interpreted scripts must be carefully managed and monitored to prevent any unauthorized script from being executed that could, in turn, compromise the integrity of the data being collected if not the fundamental integrity of the server computer system itself. Consequently, known access counters provide no solution directly in full or in part to the need to account or audit URL references to external servers based on hyper-links from previously served web pages.

The HTTP protocol itself provides for a basic server based system of URL redirection for servers and clients supporting the 1.5 or later versions of the HTTP protocol. A configuration file associated with an HTTP server (typically srm.conf) can specify a redirect directive that effectively maps a server local directory URL reference to an external URL reference through the use of a configuration directive of the form:

Redirect /dir1 http://newserver.widget.com/dir1

When a Version 1.5 or later HTTP server receives a URL reference to a local directory (/dir1) that is specified as above for redirection, a redirect message is returned to the client browser including a new location in the form of an URL (http://newserver.widget.com/dir1). This redirect URL is then used by the client browser as the basis for a conventional client URL request.

This existing server based redirection function is insufficient to support external server access tracking since, in its usual form, the redirection is of the entire directory hierarchy that shares a common redirected base directory. Even in the most restricted form, the redirection is performed on a per directory reference basis. Thus, every access to the directory, independent of the particular web page or graphics image or CGI program that is the specific object of an access request is nonetheless discretely redirected without distinction. Any potential use of the existing server redirect function is therefore exceedingly constrained if not practically prohibited by the HTTP protocol defined operation of the redirect directive.

Furthermore, the redirect directive capability of the HTTP protocol server does not provide for the execution of a CGI program or other executable coincident with the performance of the redirection thereby essentially precluding any action to capture information related to the redirect URL request. In addition, the complexity of the resource configuration file necessary to specify redirection down to a per directory configuration again raises significant configuration, maintenance and, to a lesser degree, security issues. Thus, server redirection does not possess even the basic capabilities necessary to support external URL hyper-link reference auditing or accounting.

Finally, a form of redirection might be accomplished though the utilization of a relatively complex CGI program. Such a redirection CGI program would likely need to perform some form of alternate resource identification as necessary to identify a redirection target URL. Assuming that a unique target URL can be identified, a redirection message can then be returned to a client from the CGI program through the HTTP server as necessary to provide a redirection URL to the client browser.

Unfortunately, any such CGI program would embody all of the disadvantages associated with even the simplest access counter programs. Not only would problems of execution load and latency, as well as configuration, maintenance and security remain, but such an approach to providing redirection is inherently vulnerable to access spoofing. Access spoofing is a problem particular to CGI programs arising from the fact that the HTML reference to the CGI program may be issued without relation to any particular web page. Consequently, any CGI program implementing an access counter or other auditing or accounting data collecting program can produce an artificially inflated access count from repeated reference to the CGI program HTML statement outside and independent of a proper web page. Access spoofing inherently undermines the apparent if not actual integrity of any data gathered by a CGI program. Since, at minimum, the ability to insure the accuracy of even a simple access count would be of fundamental importance to an Internet service advertiser, the use of CGI programs to provide even basic accounting or auditing functions is of limited practical use. Finally, HTML does not provide a tamper-proof way for two URLs to be accessed in sequence with just one URL reference button, such as, for example, a server CGI counter URL reference followed by external server URL reference.

SUMMARY OF THE INVENTION

Thus, a general purpose of the present invention is to provide a system and method of reliably tracking and redirecting hyper-link references to external server systems.

This is achieved by the present invention through the provision of a message to a tracking server system in response to a client system referencing a predetermined resource locator that corresponds to a resource external to the tracking server system. The tracking server system indirectly provides for the client system to have an informational element selectable by the client system, where the informational element is graphically identified on the client system with informational content obtainable from a content server system through use of a content resource locator. The informational element includes a tracking resource locator, referencing the tracking server system, and data identifying the informational element. The selection of the informational element causes the client system to use the tracking resource locator to provide the data to the tracking server system and to use the content resource locator to obtain the informational content from the content server system.

Thus, an advantage of the present invention is that URL reference data is captured in an expedient manner that interposes a minimum latency in returning the ultimately referenced web page while imposing minimum visibility of the redirection protocol on client users.

Another advantage of the present invention is that independent invocations of server external support programs and multiple external data references are not required as a consequence of the present invention, thereby minimizing the CPU and disk intensive load on the web server computer system and the resulting latency.

A further advantage of the present invention is that the reference identifier and a redirection directive can both be maintained wholly within the URL specification discretely provided by a client HTML request. Thus, the present invention is superior in both efficiency and maintenance requirements to a CGI counter, or any method that incorporates a CGI counter.

Still another advantage of the present invention is that program modifications necessary to support the protocol of the present invention are implemented entirely at the server end of a protocol transaction. Client side participation in the transaction is within the existing client side defined HTML protocol.

A still further advantage of the present invention is that the implementation of the invention introduces minimum exposure to additional security breaches due to the closed form of the protocol while providing substantial security against inappropriate URL and protocol references. This is accomplished preferably by the inclusion of validation codes inside the URL specification.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention will become better understood upon consideration of the following detailed description of the invention when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein:

FIG. 1 provides a schematic representation of client and server computer systems inter-networked through the Internet;

FIG. 2 provides a block diagram of a server computer system implementing an HTTP daemon (HTTPd) server in accordance with a preferred embodiment of the present invention;

FIG. 3 provides a flow diagram illustrating the process performed by a preferred embodiment of the present invention in receiving and processing client URL requests;

FIG. 4 provides a flow diagram illustrating the server side processing of special redirect URLs in accordance with another preferred embodiment of the present invention;

FIG. 5 provides a generalized process representation of client and server computer systems implementing the alternate processes of the present invention;

FIG. 6 is a flow diagram illustrating a server-side process that provides for the issuance of a content request message in accordance with a preferred embodiment of the present invention; and

FIG. 7 is a flow diagram illustrating a client-side process that provides for the issuance of a tracking message in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A typical environment 10 utilizing the Internet for network services is shown in FIG. 1. Client computer system 12 is coupled directly or through an Internet service provider (ISP) to the Internet 14. By logical reference via a uniform resource locator, a corresponding Internet server system 16, 18 may be accessed. A generally closed hypertext transfer protocol transaction is conducted between a client browser application executing on the client system 12 and an HTTPd server application executing on the server system 16. In a preferred embodiment of the present invention, the server system 16 represents an Internet Business Service (IBS) that supports or serves web pages that embed hyper-link references to other HTTPd server systems coupled to the Internet 14 and that are at least logically external to the server system 16.

Within this general framework, the present invention enables the tracking of the selection of embedded hyper-link references by client system 12. That is, an embedded hyper-link reference is associated with a graphical banner or other Web page element that is selectable, or clickable, by a user of the client system 12. A banner click on a client system is typically made to obtain information, identified in some fashion by the banner graphic that is of interest to the client system user. Tracking is preferably enabled by embedding HTML information in the Web page served to the client system 12. This information is served from any prearranged HTTPd server system to the client system 12. The prearrangement is with an IBS to track banner clicks, on Web pages served by or on behalf of a designated tracking HTTPd server system, such as system 16, that operates to collect the served page provided tracking information.

The embedded information is, in accord with the present invention, sufficient to enable the client computer system 12 to provide tracking information to the HTTPd server system 16. As will be seen, this information is also sufficient, directly or indirectly, to enable the client computer to request the information associated with the banner graphic. As will also be seen, there are a number of possible implementations of the present invention. These implementations can generally be categorized as predominately using either a server-side or client-side process, as involving proprietary, plug-in, and interpreted control processes, and as using any of a number of specific data transfer protocols.

The preferred embodiment of the present invention utilizes a server-side process implemented as a proprietary modification to the HTTPd server application executed by the server system 16 and that uses the HTTP redirection directive. Thus, a web page served by an HTTPd server system, such as the server system 16 or another server system (not shown) to the client 12 embeds a URL reference to a web page served by the logically external server system. Selection of this embedded URL through the client browser of the client computer system 12 results initially in an HTTP transaction with the server system 16 rather than the external server. The information stored in the embedded URL first served with the web page to client system 12 is thus provided back to the server system 16 upon selection of the URL even though the apparent target of the URL is the external server system. A redirection response is then provided by the server system 16 to the client system 12 providing the corresponding redirection URL.

As shown in FIG. 2, the server system 16 receives the redirection request information via a network connection 20 to a network interface 22 within the server system 16. The network interface 22 is coupled through an internal bus 24 to a central processing unit (CPU) 26. The CPU 26 executes a network operating system 28 in support of the network interface 22 and other functional aspects of the server system 16. The network operating system 28 supports the execution by the CPU 26 of an HTTPd server application 30 that defines the responsive operation of the server system 16 to HTTP requests received via the network 20. Finally, the network operating system 28 provides for temporary and persistent storage of data in a mass storage device 32 preferably including a persistent storage media such as provided by a conventional hard disk drive.

In accordance with the preferred embodiment of the present invention, the embedded redirection information provided as part of a URL HTTP request is processed by the HTTPd server 30. Preferably, the processing by the HTTPd server 30 is performed through the execution of the server 30 itself as opposed to the execution of any external CGI programs or the like. The redirection information is processed by the execution of the server 30 to identify and validate the particular URL reference that provided the redirection information and to generate a redirection target URL.

In a preferred embodiment of the present invention, an embedded URL containing redirection information is formatted as follows:

http://<direct_server>/redirect?<data>?http://<redirect_server>

The direct_server portion of the embedded URL specifies the HTTP server target of a transaction that is to be initially established by the client system 12. The remaining information is provided to the tracking or targeted direct server. The direct server may be any HTTPd server accessible by the client system 12 that has been designated to service redirection requests in accordance with the present invention.

The term "redirect" in the embedded redirection URL is a key word that is pre-identified to the HTTPd server 30 to specify that the URL corresponds to a redirection request in accordance with the present invention. Although the term "redirect" is the preferred term, any term or code may be selected provided that the term can be uniquely identified by the HTTPd server 30 to designate a redirection URL. The recognition processing of the "redirect" term is preferably performed through the execution of the server 30 by way of a corresponding modification to the HTTPd server application. That is, the HTTPd server application is modified to recognize the term "redirect" as a key word and to execute a subprogram to implement the server-side process of this preferred embodiment. Alternately, the modification to the HTTPd server application can be implemented as a "plug-in" binary program operative through a conventional interface provided with the HTTPd server application to obtain essentially the same functionality. Although of possibly lesser performance, a server application embedded language, such as Java.RTM. or JavaScript.RTM., may be also alternately used to implement the server-side process of recognizing the "redirect" key word and performing the further processing to implement the present invention.

The "data" term of the redirection URL provides reference identifier data to the HTTPd server 30 that can be used to further identify and potentially validate a redirection URL to the HTTPd server 30. The data thus permits an accounting of the redirection URL to be made by the HTTPd server 30. In the context of an advertisement, the data may encode a particular advertising client for whom access data may be kept, a particular instance of the graphic image provided to a client system 12 in association with the redirection URL, and potentially a validation code that may serve