Abstract:
A method of interactively sharing information between at least two devices in a computer network, each device having a respective browser associated therewith for handling the information, includes retrieving information from an information source in the network for storage in response to receipt of a retrieval request from a first browser associated with a first device. The method further includes sending the stored information to at least a second browser of at least a second device in response to receipt of a similar request therefrom, the second device receiving the request from the first device, such that the devices can share the information retrieved from the information source in response to the single request made to the source. Preferably, a surrogate is established in at least the first device for informing the second device of the request made such that the browser of the second device can make the similar request. Also, the information available from the information source in the computer network may include dynamically changing (i.e., stateful) content.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of the pending U.S. patent application identified as Ser. No. 09/227,522 filed Jan. 8, 1999 and entitled “Methods and Apparatus for Enabling Shared Web-Based Interaction in Stateful Servers,” hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and apparatus for providing shared web-based interaction and, more particularly, to providing shared web-based interaction involving dynamically generated or stateful content. 
     BACKGROUND OF THE INVENTION 
     A browser is a software program run on a computer that allows a computer user to request, view, manipulate and/or send information across a computer network. For example, a web-based browser serves as a user&#39;s front-end interface to the World Wide Web (WWW) on the Internet. As is known, using a web-based browser, a user types in or selects the address or URL (Uniform Resource Locator) of a website to request a webpage (e.g., homepage) associated with the website that he wishes to visit. The browser transmits the request over the Internet to the Web server with which the website is associated and the server downloads the homepage to the browser for viewing by the user. The homepage is typically an index to other pages on that website that can be accessed by clicking on icons which represent the addresses of the other pages. 
     In U.S. Pat. No. 5,991,796, issued Nov. 23, 1999 and entitled: “Technique For Obtaining And Exchanging Information On World Wide Web,” which is a continuation of U.S. Pat. No. 5,862,330, issued Jan. 19, 1999 with the same title, a technique is disclosed for shared Internet browsing among multiple users (e.g., clients) using unmodified browsers and servers. The technique employs client-side executable content that is dynamically downloaded into the browser, such as an applet. An applet is a limited-function, utility program. The applet at one endpoint communicates with an applet of a collaborator (e.g., another browser) via some communication channel, and allows the “connected” browsers to move from webpage to webpage in synchrony, viewing the same (or related) content. One way of achieving this interaction is to have all connected browsers submit the same URL. However, in the case of dynamically generated content, this causes the Web server to execute the same request multiple times, once for each participating browser (i.e., as many times as the same request was respectively made by the multiple users). This may not be desirable, particularly, when a URL submission causes an order to be placed on the Web server. That is, multiple executions of the request will cause multiple orders to be placed on the Web server. This may not be what the multiple users intended in participating in the shared browsing session. That is, the intent may have been only to place a single, joint order at the end of the shared browsing session. 
     For example, various e-commerce websites accessible via specific Web servers allow users to select items they wish to order and place them in a virtual “shopping cart.” When the user completes his selections, he then clicks on a “Place Order” icon resulting in a URL request being submitted to the e-commerce server for placement of the order. However, if multiple users are interactively browsing in order to place one joint order, as described above, then when one user clicks on the “Place Order” icon, each browser submits an identical URL request. This has the undesirable effect of placing as many orders for the same items as there are connected browsers. 
     Proxy servers have been proposed for improving access to data on the Internet. A proxy server is a facility used by a client (i.e., like a browser) which receives a request for a particular URL from a client (e.g., a Web browser) and forwards the request (on behalf of the client, as its proxy) to the appropriate Web server. The proxy server receives the response and transmits the response to the requesting client. A firewall proxy, for example, accepts requests from a client inside the firewall for data provided by servers outside the firewall, and retrieves the data. A caching proxy server additionally saves the obtained response, and provides the response to any other client that autonomously makes the same request, subject to certain rules which govern how long data will be held in the cache, and when it will be refreshed. 
     However, caching proxy servers do not cache responses that are dynamically generated, e.g., output of CGI (Common Gate Interface) requests, Active Server Pages, etc. For example, a financial information website accessible via a particular Web server may have a feature that allows a user to request and receive a price quote on a particular stock. For instance, clicking on a “Get Quote” icon will result in a URL request being submitted to the Web server. The Web server may then have to search for the latest stock quote or, itself, request and retrieve the latest stock price from another source. Assuming the user sets up a caching proxy server, a price quote requested by a user in the morning will be retrieved and cached in the caching proxy server. However, if the user clicks on the “Get Quote” icon in the afternoon, the caching proxy server still only has the morning price quote stored, which is likely no longer accurate. Since the caching proxy server does not dynamically update the information, a new request must be placed to the website. 
     Further, proxy servers require changes in the client-side browser configuration. That is, the user must manually modify the browser settings to direct all URL requests to the proxy server, which then makes the request. Still further, attempting to use a proxy server in conjunction with shared browsing does not work in the presence of a firewall. That is, the browser can only use one proxy at a time, whereas two are needed, i.e., one to get outside the firewall, and the other one to support the shared interaction. 
     SUMMARY OF THE INVENTION 
     The present invention provides methods and apparatus for permitting interactive browsing over a computer network such that multiple users (e.g., clients) are provided with dynamically generated content (i.e., data that is subject to state changes) retrieved from an information source in the network when needed. The disclosed techniques do not require any client-side modifications and operate transparently even in the presence of a firewall. 
     Advantageously, the present invention provides these and other inventive features by employing an intermediary network element, referred to as a gateway, situated between user devices and information sources in a computer network. The gateway enables a method of interactively sharing information between at least two devices in the computer network, each device having a respective browser associated therewith for handling the information. The method includes retrieving information from an information source in the network in response to receipt of a request, from a first browser associated with a first device, to retrieve the information. The retrieved information is stored in association with the request received from the first browser. Preferably, this is accomplished via a cache memory associated with the gateway. The method also includes sending the stored information to at least a second browser of at least a second device in response to receipt of a similar request therefrom such that the devices can share the information retrieved from the information source in response to the single request. It is to be appreciated that the second browser receives the request from the first browser so that it can make the similar request to the gateway. In this manner, the original request from the first browser is executed by the information source only once, but shared by multiple user devices. The gateway may be implemented at a server in the network, at any of the user devices, or even at the information source. 
     In another embodiment of the invention, surrogate applets are preferably dynamically downloaded from the computer network to at least some of the browsers of the devices participating in the interactive browsing session. The surrogate applets are executable code that serve as interfaces between the browsers, as well as translators of browser requests. The requests are translated or modified by the surrogates so that they can be directed to the gateway by the respective browsers. 
    
    
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustrating a server system for the establishment of surrogates which may be employed with the invention; 
     FIGS. 2A and 2B are flow charts jointly illustrating the steps in carrying out the operation of the server system of FIG. 1; 
     FIG. 3 is a block diagram illustrating an exemplary embodiment of a web-based interactive browsing arrangement according to the present invention; 
     FIG. 4 is a block diagram illustrating a client-server system in which web-based interactive browsing according to the invention may be implemented; and 
     FIGS. 5A through 5D is a flow chart illustrating a web-based interactive browsing method according to an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention will be described below in conjunction with an exemplary web-based browser and web server arrangement that is compatible with standard web-based browsers such as, for example, the NETSCAPE browser (available from Netscape Communications Corporation), the standard hypertext transfer protocol (HTTP), and hypertext markup language (HTML). Although particularly well-suited for implementation over the Internet using Transmission Control Protocol/Internet Protocol (TCP/IP) connections, the invention is not limited to use with any particular type of network or network communication protocol. The disclosed techniques are suitable for use with a wide variety of other networks and protocols, and many different types of browsers installed on client computers. Further, the term “processor” as used herein is intended to include any processing device, including a CPU (central processing unit), which may be utilized in a client computer, server computer, or any other computer employed in conjunction with the invention. Also, the term “memory” as used herein is intended to include memory associated with a processor or CPU, such as, for example, RAM, ROM, a fixed memory device (e.g., hard drive), or a removable memory device (e.g., diskette). In addition, the processing device may include one or more input devices, e.g., keyboard, for inputting data to the processing unit, as well as one or more output devices, e.g., CRT display and/or printer, for providing results associated with the processing unit. Further, it is to be understood that one or more processing devices within the network may share associated resources. Accordingly, the software instructions or code for performing the methodologies of the invention, described herein, may be stored in one or more of the associated memory devices (ROM, fixed or removable memory) and, when ready to be utilized, loaded into RAM and executed by a CPU. 
     Before providing a detailed description of preferred embodiments of interactive browsing methods and apparatus of the invention, an explanation will follow as to a preferred method for establishing a surrogate on the computer of each user who wishes to participate in an interactive browsing session. This method is described in the above-referenced U.S. Pat. Nos. 5,991,796 and 5,862,330. 
     FIG. 1 illustrates a server system  100  which is connected to the World Wide Web (WWW) as a web server. System  100  works compatibly with standard web browsers such as the NETSCAPE browser, HTTP and HTML. Among other things, system  100  provides users with services of: (a) collaborative browsing of HTML documents at various websites on WWW, and (b) real-time interactive communications between the users. Specifically, with system  100 , during a collaborative browsing session, multiple users or collaborators are allowed to synchronously and cooperatively browse information from websites addressable by their uniform resource locators (URLs). The collaborators may also interact with one another through text-chat communications for example. In addition, system  100  allows users to freely join and exit an on-going session and is capable of scaling its capacity to accommodate a changing number of sessions and collaborators in a particular session. 
     As shown in FIG. 1, a user may utilize computer U- 1  to access system  100  over WWW at a predetermined URL. Computer U- 1  may be a conventional personal computer (PC) running standard web browser  151  such as the NETSCAPE browser. As soon as U- 1  is connected to system  100  through link  105 , manager  107  in system  100  starts communicating with U- 1  through web browser  151  and HTTP server  109  having a common gate interface (CGI). 
     Manager  107  comprises a service routine for helping a user to establish a collaborative browsing session. FIGS. 2A and 2B illustrate the steps of the service routine. At step  201 , manager  107  causes a “homepage” to be displayed on U- 1 , which greets the user, and describes the service provided by system  100 . Manager  107  then elicits from U- 1  user information, as indicated at step  203 . This information includes a user identification (ID), password and other administrative data necessary for ensuring that the user is an authorized user. At step  205 , manager  107  inquires U- 1  as to whether the user wants to create a session, or join an on-going session. In this instance, the user of U- 1  chooses to create a session. Manager  107 , at step  207 , then prompts the user for the details on the session to be created, such as the purpose or the topic of the session, and whether it is a private or public session. By way of example, if it is a private session, a would-be collaborator must identify the user, by his/her user ID, who created the session in order to join it. If it is a public session, the topic of the session will be listed and is searchable by a would-be collaborator. 
     In this instance, the user of U- 1  replies that the session to be created is public and the purpose of the session is to, for example, shop for an automobile. Manager  107  proceeds to start the new session and causes surrogate  153  to be created within browser  151  in computer U- 1 , as indicated at step  209 . To that end, system  100  transmits to computer U- 1  mobile code pursuant to a mobile programming language such as, for example, the standard JAVA language. Thus, in this instance, the mobile code may be in the form of a JAVA applet. Surrogate  153  is realized when the applet starts to run within browser  151  as soon as it reaches computer U- 1 . Surrogate  153  is further described hereinbelow, and it suffices to know for now that it serves as an assistance to the browser to carry out the session. 
     Since in this instance it is a new session, manager  107 , at step  211 , assigns a new controller, numerically denoted  111 , to control and regulate the session. Manager  107  at step  213  causes controller  111  to be connected to surrogate  153  through link  113 , and at the same time discontinues link  105 . Surrogate  153  serves as an interface between browser  151  and controller  111 . Among other things, surrogate  153  monitors user interaction with the browser, and reports the user interaction to controller  111 . 
     It should be noted at this point that surrogate  153  is realized using a JAVA applet which is transmitted to and executed on U- 1  on an on-demand basis, no software needs to be installed or maintained on the user computer beforehand as in the traditional applications. Thus, any standard JAVA-enabled browsers such as, for example, the NETSCAPE browser can be utilized. However, other browsers that support executable content may be employed. In other words, system  100  does not require the users to have specialized browser software to take advantage of the service. 
     A second user may utilize computer U- 2  to access system  100  at the predetermined URL to join an on-going session. After computer U- 2  establishes a link (not shown) to HTTP server  109 , manager  107  similarly goes through steps  201  and  203  of FIG. 2A, as previously described. However, at step  205 , the user of U- 2  in this instance chooses to join an on-going session. As such, manager  107  queries U- 2  as to whether the second user wants to join a private session or public session, as indicated at step  220  in FIG.  2 B. In this instance, the second user chooses to join a public session, and manager  107  proceeds to step  224 . Otherwise, the second user needs to identify the private session to be joined by the user ID of the creator of that session, as indicated at step  222 . 
     In any event, at step  224 , manager  107  causes a list of all the on-going sessions to be displayed on computer U- 2  including, for example, the automobile shopping session created by the user of computer U- 1 . Manager  107  then proceeds to step  226  where it determines the particular session selected by the second user. In this example, the second user chooses to join the automobile shopping session by pointing and clicking using a mouse device at the listed topic. At step  228 , surrogate  173  is created on computer U- 2 , in a manner described before, within browser  171  which may be different from browser  151 . Once surrogate  173  is created, knowing that the automobile shopping session was assigned to controller  111 , manager  107  causes controller  111  to be connected to surrogate  170  through link  175 , as indicated at step  230 . 
     In this particular example, the creator of the session is afforded the same capabilities as the other collaborators, except that the creator has the control of leading the session. In addition, the surrogates connected to controller  111  are programmed to allow the collaborators to interactively communicate in text with one another in real time. The collaborators may point and click at a specified icon on their computers using a mouse device to make the text-chat connections for exchanging their opinions on automobiles as the HTML documents unfold before them. However, it will be appreciated that a person skilled in the art may program controller  111  to enforce certain access control. For example, different collaborators may be afforded by controller  111  different capabilities during a collaborative session. Controller  111  may also enforce a priority scheme whereby the collaborators take turns to lead the session and communicate with one another. 
     Other computer users who want to either create a session or join an on-going session go through the similar process to that of U- 1  or U- 2  described above. However, a controller may be overloaded at certain point as more and more collaborators joining a particular session regulated by the controller. Because of the server-based architecture of system  100  where intelligence and information on every user&#39;s connection resides in manager  107 , the system capacity is readily scalable to accommodate a growing number of the collaborators, without affecting the service quality. Once the number reaches a predetermined threshold at a controller, manager  107  employs a new controller to connect the excessive collaborators. The new controller and existing controllers for the same session dynamically reorganize themselves in a hierarchy (e.g., star topology) to facilitate communications with one another and their coordination to carry out the session in a synchronous manner. 
     Furthermore, as more and more controllers are engaged, the initial capacity of system  100  may run out. Again, because of the architecture of system  100 , a new controller may be engaged using additional hardware which can be easily absorbed into system  100 . Similarly, when the number of sessions exceeds a predetermined threshold, multiple managers similar to manager  107  are instituted and the managers are dynamically reorganized in a particular hierarchy (e.g., star topology). 
     A text-chat communications capability between the collaborators is provided through the cooperation of the surrogates. Other means of communications can also be provided, in addition to or in lieu of the “text chat” communications, using the surrogates. These other communications means include standard telephone, Internet phone, packet phone and video conferencing facilities. 
     Finally, system  100  is disclosed herein in a form in which various system functions are performed by discrete functional blocks. However, any one or more of these functions could equally well be embodied in an arrangement in which the functions of any one or more of those blocks or indeed, all of the functions thereof, are realized, for example, by one or more appropriately programmed processors. 
     Given the above description as to a preferred method of establishing surrogates in browsers, methods and apparatus for interactive web-based browsing according to the invention will now be described. 
     Referring now to FIG. 3, portions of an interactive browsing system  300  according to an exemplary embodiment of the invention are shown. The system  300  includes a first browser  302  having a surrogate  304  associated therewith. As previously explained, the browser  302  is a computer software program that runs on a computer of the system  300  and allows a user, inter alia, to place information requests to various websites associated with network servers. The surrogate  304  is also a computer software program that is run in conjunction with the browser  302  on a computer of the system  300  and, as will be explained, provides the necessary functionality to provide interactive browsing between browser  302  and other browsers according to the invention. It is to be appreciated that the surrogate  304  is executable content that may preferably be dynamically downloaded into each client that is participating in the interactive browsing arrangement. That is, the invention contemplates each user downloading a surrogate applet from a designated network server (e.g., server  100 ) to his computer when he intends to interactively browse websites with another user. The surrogate is preferably established at the user&#39;s computer via the server system  100  and techniques described above with respect to FIGS. 1,  2 A and  2 B. The system  300  of the invention also includes a second browser  306  with a second surrogate  308 , which provide similar functionality to another user as the browser  302  and surrogate  304  provide to the first user. The surrogate  304  may also be established in conjunction with server system  100 . The surrogates  304  and  308  are coupled to one another via communications channel  310 . It should also be understood that more than two users may be coupled via their respective surrogates in this manner. 
     Further, the interactive browsing system  300  of the invention includes an intermediary element  312 , hereinafter referred to as a “gateway.” The gateway  312  is advantageously coupled between the surrogates  304  and  308 , respectively via communication channels  316  and  318 , and a WWW server  320 , via a communications channel  322 . It is to be appreciated that while FIG. 3 illustrates only one WWW server in system  300 , the gateway  312  may preferably be coupled to more than one or all such servers on the Internet. The gateway  312  also includes a cache memory  314  for storing information, as will be explained below, in accordance with the invention. 
     Advantageously, a surrogate ( 304  or  308 ) intercepts URL requests from its associated browser ( 302  or  306 ) that are directed to the Web server  320  responsible for retrieving and/or generating the requested content (e.g., HTML document). The surrogate may intercept all URL requests made by a user via the browser or only requests matching some specified criteria. The initiating surrogate via its associated browser directs the request to the gateway  312  (via channel  316  or  318 ). The gateway then sends the URL request to the Web server  320  (via channel  322 ), stores the response(s) received from the server  320  (via channel  322 ), and directs the initiating surrogate via its associated browser to retrieve the stored response (via channel  316  or  318 ). The initiating surrogate then preferably directs all other connected surrogates (via channel  310 ) to retrieve the response via their associated browsers from the gateway  312 . This may be done, for example, through the controller  111  in server system  100  (FIG.  1 ). Advantageously, the original request is thus executed only once by the WWW server  320 , while the response is shared by multiple endpoints via the intermediary gateway. 
     FIG. 4 illustrates a client-server system in which web-based interactive browsing according to the invention may be implemented. As shown, a client computer  402  (client  1 ), a client computer  404  (client  2 ), a gateway  406 , and a server  408  are coupled via respective communications channels over the WWW network  410 . Client  402  includes a processor  412  and associated memory  414  for, e.g., running the browser  302  and surrogate  304  according to the invention, as described herein. Likewise, client  404  includes a processor  416  and associated memory  418  for, e.g., running the browser  306  and surrogate  308  according to the invention, as described herein. Gateway  406  includes a processor  420  and associated memory  422  for performing the operations of the gateway  312 , as described herein. It is to be appreciated that the cache  314  may be part of the memory  422 . The server  408  includes a processor  424  and associated memory  426  for performing the operations associated with the WWW server  320 . It is to be understood that the communications channels  310 ,  316 ,  318 , and  322  of FIG. 3, maybe implemented as TCP/IP connections, as are known in the art, over the WWW  410  in FIG.  4 . 
     While the gateway  312  is shown in FIG. 4 as being implemented on a separate computer, it is to be appreciated that this is not necessary for the invention. That is, the gateway  312  may be alternatively implemented on the server  408 , or at either client computers  402  or  404 . Still further, the gateway  312  may be implemented on the server system  100  (FIG. 1) used to establish the surrogates in the client computers. That is, the particular computer employed to execute the functions of the gateway is not critical to the invention. Also, it should be understood that the server  408  could be the same server that aids in establishing the surrogates in the browsers (e.g., server system  100  in FIG.  1 ). 
     Referring now to FIGS. 5A through 5D, a flow chart of a web-based interactive browsing method  500  according to an exemplary embodiment of the present invention is shown. In step  502 , a user requests a URL using browser  1  (browser  302 ). Then, in step  504 , the surrogate applet  1  (surrogate  304 ) intercepts the request and translates the request. Translation includes modifying the URL request such that an address associated with the gateway  312  is included therewith. In this manner, the request is first directed to the gateway rather than directly to the intended server. The browser  1  then sends the translated URL request to the gateway, in step  506 , which is received by the gateway, in step  508 . 
     Next, the gateway  312  searches its cache  314  for the translated URL (step  510 ). Assuming that this is the first time the browser  1  is requesting the URL in this session, the gateway does not find the URL in its cache. In step  512 , the gateway then performs a reverse translation of the URL (e.g., removes any modification made to the request by surrogate applet  1 ) and forwards the original URL request to WWW server  320 . 
     WWW server  320  then fulfills the request and sends the response (e.g., HTML document) back to the gateway  312 , in step  514 . The gateway receives the response, modifies it as necessary, and saves the response in its cache (step  516 ). That is, in its cache memory, the gateway associates the translated URL request received from browser  1  with the received response. In step  518 , the gateway sends a copy of the cached response back to browser  1 , which displays the contents of response to the user, in step  520 . 
     Next, in step  522 , surrogate applet  1  sends the translated URL request to surrogate applet  2  (surrogate  308 ). In response, surrogate applet  2  requests associated browser  2  (browser  306 ) to retrieve the translated URL via gateway  312  (step  524 ). Browser  2  then sends the translated URL request to the gateway, in step  526 , which is received by the gateway, in step  528 . The gateway then searches its cache for the translated URL. Since, in step  516 , the gateway saved the translated URL in conjunction with the response received from the WWW server, the gateway locates the translated URL request (step  530 ). The gateway sends a copy of the cached response back to browser  2 , in step  532 . Browser  2  then displays the contents of the cached response to its associated user, in step  534 . 
     Also, it is to be understood that browser  2  may initiate a translated URL request to the gateway, in which case, browser  1  is the recipient of the copy of the cached response. It is to be further understood that steps  522  through  534  are performed for each browser connected to browser  1 . 
     Advantageously, in this manner, multiple users may participate in interactive browsing that involves dynamically generated content associated with stateful servers. That is, referring back to the e-commerce website example previously mentioned, if a user associated with browser  1  and a user associated with browser  2  are jointly viewing and selecting items available on the website, a URL request to place an order for the selected items is only generated once at the subject server, i.e., in response to the initiating surrogate. Then, all other connected browsers may review the results of the single order. By way of another example, when the initiating user clicks on a “Visitors Count” icon on a webpage, which gives the user the current number of persons visiting the site (incremented by one to include the user), only one URL request is sent to the subject server, rather than a request for each connected browser. 
     Further, unlike a conventional arrangement that employs a caching proxy server, an interactive web-based browsing system according to the invention permits the use of a firewall. That is, the firewall may be placed between the gateway  312  and any WWW server such as, for example, server  320  (FIG.  3 ). For example, the firewall may be implemented in the same computer device that implements the gateway, e.g., computer  406  (FIG.  4 ), or in its own dedicated computer device. 
     Still further, it is to be appreciated that each user participating in an interactive browsing session according to the invention does not necessarily need to establish a surrogate applet in his browser. That is, for example, a user can receive the translated URL from the other browser, via the controller of server system  100  (FIG.  1 ), and then manually enter the translated URL to be sent to the gateway  312 . In this manner, the user operating his browser without a surrogate can also get a copy of a HTML document requested by another participating browser using a surrogate. 
     One of ordinary skill in the art will realize that the teachings of the invention described herein can be applied to many and varied applications. By way of example only, it is to be understood that the techniques of the invention have application in Web-based call centers where customer service agents interact with customers. In such an application, the interaction between agent and customer may involve changes in server-side state (e.g., financial transactions, order placement, etc.), but there is a need to have the agent and customer see the same content. Thus, referring to FIG. 4, if computer  402  is an agent and computer  404  is a customer, such requirements as mentioned above are satisfied according to the invention. That is, by employing a gateway, the agent and customer could both view dynamically generated (i.e., stateful) content provided by server  408 . 
     Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention.