Abstract:
A method for dynamically adding new functionality to a first set of instructions that processes Web documents. The invention includes the first step of the first set of instructions decoding a first statement of the Web document. The first statement includes a first command and at least one instruction provided as an argument to the first command. In response to executing the first command, the first set of instructions decodes the instruction provided as the argument to the first command and issues the instruction to be executed. Executing the instruction provided as an argument to the first command, results in new Web document processing functionality being added to the first set of instructions.

Description:
This is a continuation of application Ser. No. 08/673,956 filed Jul. 1, 1996, now U.S. Pat. No. 5,845,075. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to data processing in computer systems, and in particular, dynamically adding functionality to a Web browser from a Web document. 
     BACKGROUND OF THE INVENTION 
     Networking technology has developed a large network of networks, referred to as the Internet, which interconnects millions of computers around the world. The Internet allows the transfer of data between any number of computer systems connected to the Internet using the Transmission Control Protocol/Internet Protocol (TCP/IP). Computers responding to service requests from other computers, via the Internet, are commonly referred to as servers, and computers that initiate requests for service from a server are referred to as clients. 
     The Internet has become very popular in part due to the World Wide Web (WWW), which is a network of links to hypertext documents operating within the Internet. These hypertext documents are referred to as either Web documents, Web pages, or hypertext documents. Web documents are embedded with directly accessible connections or links to other documents which create a non-linear way of reading the document. The links are embedded in Web documents as a phrase of text or an image which can be selected and activated by a computer user. Information about the Web documents are controlled and provided by Web servers. At the user&#39;s end, a Web client takes the user&#39;s requests and passes them on to the Web server. 
     The Web documents are written with a high level programming language referred to as the Hypertext Markup Language (HTML). Commands of the HTML, hereinafter referred to as tags, provide a variety of functions including, but not limited to, defining special format and layout information in a Web document, embedding images and sound in a Web document, and embedding links to other Web documents. 
     In order to access, process, and display a Web document, a client uses a first set of instructions, referred to as a browser. The browser typically includes a set of browser commands corresponding to the tags available in the HTML. Each browser command in turn points to a procedure of one or more instructions defining the command which, when executed, provide a functionality of the respective command. If the client requires service from the Web server, the browser uses the Hypertext Transfer Protocol (HTTP) to communicate with the server. 
     The browser compares each tag found embedded in a Web document with the set of browser commands. Once a match is found, the browser executes the procedure corresponding to the matched browser command in order to provide the functionality of the respective command. 
     The instructions of the browsers are typically written with a programming language different from the HTML, which includes a library of several routines. The library of routines can in turn be used to develop and add new browser commands, or modify existing browser commands, which can be embedded in a Web document as new or modified tags to provide new functionality when displaying the Web document. 
     The need for new browser commands, or to modify an existing browser command, is typically recognized (at the site of the server) when writing a Web document. For example, a programmer writing a Web document may want to use a new tag to display selected text on a Web document in color. However, before the new command can be embedded in a Web document as a new tag and properly executed, a browser command corresponding to the new tag must first be defined and implemented on the client&#39;s browser which is going to access and display the Web document. 
     Conventionally, instructions defining new browser commands, or modifying existing browser commands, are manually added to the browser by the client when the browser is not in use (i.e., offline). However, this procedure is inefficient because the client must take the time to manually add the new instructions every time a new command, or modified existing command, is to be added to the browser, regardless of whether the new or modified command will be used in other Web documents. Moreover, the procedure is impractical because the client may not have access to the instructions defining the new or modified command, and usually doesn&#39;t know when it is necessary to add instructions to define new or modify existing commands. 
     It is also impractical for a server to add the instructions to a client&#39;s browser because servers are generally unaware of which potential clients are going to access their Web documents. Moreover, a server rarely has access privileges to enter a client&#39;s browser and add additional instructions. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention provides a method for dynamically adding new functionality to a first set of instructions that processes Web documents. The invention includes the first step of the first set of instructions decoding a first statement of the Web document. The first statement includes a first command and at least one instruction provided as an argument to the first command. In response to executing the first command, the first set of instructions decodes the instruction provided as the argument to the first command and issues the instruction to be executed. Executing the instruction provided as an argument to the first command, results in new Web document processing functionality being added to the first set of instructions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which: 
     FIG. 1 illustrates a computer system, connected to a server, wherein the computer system is capable of dynamically adding or modifying instructions in a Web browser, according to one embodiment of the invention. 
     FIG. 2 illustrates a flow diagram illustrating the steps of adding instructions to a Web browser from a Web document when the Web browser is interpreting the Web document, according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     One embodiment of the invention provides a method and apparatus for dynamically adding or modifying functionality of a Web browser. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
     FIG. 1 illustrates a block diagram of a computer system  100  capable of adding functionality to a Web browser  108  from a Web document  104  when the Web browser  108  is processing the Web document  104 , according to one embodiment of the invention. The computer system  100  includes a Web browser  108  stored in main memory  106  for accessing and processing the Web document  104  provided by a server  102 . The computer system  100  further includes a processor  124  and a network connector  116  coupled to a bus  120 . The network connector  116  is further coupled to a network  118 . 
     In one embodiment of the present invention, the browser  108  is written in the Tool Command Language (Tcl) programming language, which is an interpreted language (i.e. each statement of code is decoded and executed before the next line of code). In alternative embodiments, the browser may be written in other interpreted languages that allow extension of applications. 
     As illustrated in FIG. 1, computer system  100  is shown accessing, interpreting, and displaying a Web document  104  provided by the server  102 . After the Web document  104  is transferred from the server  102  to the main memory  106  of client  100 , the Web document  104  is interpreted by the client  100 . 
     In the example shown in FIG. 1, the content of sample Web document  104  is illustrated within main memory  106  as including instructions to be added to the Web browser  108 , which define a new browser command (i.e. the argument to the &lt;New_Code&gt; 128  command) to be added to the browser&#39;s  108  set of browser commands  110 . The interpreted Web document  104  is in turn shown on display  122 , displaying the functionality of the new browser command. The novel way in which the present invention enables this dynamic modification of a browser is described in detail in the following sections. 
     FIG. 2 illustrates a flow diagram of the steps performed in order to add functionality to a Web browser from a Web document when the Web browser is processing the Web document, according to one embodiment of the present invention. In block  202 , the browser  108  stored in computer system  100  accesses a Web document  104  provided by the server  102 . In block  204 , the interpreter  114  of the browser  108  reads a single statement of code provided in the Web document  104 . In block  206 , the interpreter  114  parses the statement into tags and arguments. 
     In block  208 , the interpreter  114  compares any tags found in the statement with the set of browser commands  110  provided in the browser  108 . In one embodiment of the invention, the set of browser commands  110  includes a command, hereinafter referred to as the “New_code” command, which accepts additional instructions as its argument. When executed, the New_code command causes the instructions provided as its argument to be passed to the interpreter  114 , wherein the instructions are parsed and executed. In one embodiment of the invention, the New_code command is generated in part using the conventional “eval” command of the Tcl programming language. 
     In decision block  210 , it is determined whether the statement of code read from the Web document includes the New_code command. If the New_code command is included in the statement, then in block  212 , the instructions provided as the argument to the New_code command are passed to the interpreter  114 , where they are parsed and executed as previously described. 
     In one embodiment of the invention, the instructions provided as the argument to the New_code command may define a new command or modify an existing browser command. The new command, or modified existing command, may provide new functionality to the browser, which typically includes, but is not limited to, modifying an appearance of a Web document, embedding-multimedia data in a Web document, and/or embedding in a Web document a link to a separate discrete unit of information. 
     The instructions provided as the argument to the New_code command are encoded using the library of routines belonging to the conventional programming language used to write the Web browser  108 . The new or modified browser commands may correspond to new HTML tags, which may be used to modify the appearance of a Web document, define special formats and layout information of a Web document, embed images and sound in a Web document, or embed links to other Web documents. 
     The new or modified existing browser commands may be enforced for the duration the present Web document is displayed, or optionally, enforced for the life of the browser  108 . The instructions provided as an argument to a New_code command may also be used to replace the client&#39;s existing browser with a new browser. 
     In an alternative embodiment, the instructions provided as the argument to the New_code command may include a Uniform Resource Locator (URL), which provides an address to a separate Web document having instructions that define a new command or modify an existing browser command. The instructions may be downloaded to the client from the separate document and processed as described in block  212 . 
     FIG. 1 illustrates an example of using the New_code command to add a new command to the browser. As illustrated, the third statement in the Web document  104 , shown stored in the main memory  106 , includes a New_code command  128  followed by the instructions to add a new browser command, “H3”, which when executed will cause selected text to be displayed in color. 
     In response to executing the New_code command, the interpreter adds the command H3  130  to the set of browser commands  110 , and further adds the definition  132  of H3 to the set of procedures  112 . The H3 command is then used as a tag in the next statement of the same Web document to have selected text of the Web document displayed in color, as indicated on display  122 . 
     In addition, in FIG. 1, the Browser  108 , which includes the Interpreter  114 , the Procedures  112 , the Commands  110 , could alternatively be stored on another computer-readable medium, including magnetic and optical disk, which could be accessed via a disk drive coupled to the client&#39;s computer system. 
     In decision block  210 , if it is determined that the command embedded in the statement being interpreted is not a New_code command, then in block  214 , the interpreter  114  executes the procedure corresponding to the command in order to provide the functionality of the command. 
     In decision block  216 , it is determined whether additional statements remain to be processed in the Web document  104 . If no statements remain to be processed, the Web document remains displayed until a user of the computer system  100  exits the Web document using conventional means. On the other hand, if statements remain to be processed, the remaining statements are sequentially processed in steps similar to those described in blocks  204 - 216 , wherein the individual statements are parsed and executed in order to provide the functionality of each command embedded in the statement. 
     The apparatus and method of the present invention for dynamically adding or modifying functionality of a browser from a Web document when the browser is interpreting the Web document provides many advantages. For example, servers can provide Web documents using new tags and the browser commands corresponding to the new tags without regard to the commands available on a client&#39;s browser and be assured that the tags will be executed as defined by the server. 
     The present invention also allows the browser commands corresponding to the new tags to be transparently added to the client&#39;s browser. As a result, the client does not have to know when, or how, a new or modified command is to be defined on their browser. 
     In addition, the present invention can also be used to conserve memory space, which may be critical on a limited resource set top box. For example, a new or modified existing browser command may only be applicable to a new tag being used in the present Web document. In such a case, the functionality to be added to a Web browser can be defined to only remain on the browser for the duration of the present Web document&#39;s display. 
     In the foregoing specification the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. Moreover, the following claims indicate the scope of the invention, and all variations which come within the meaning and range of equivalency of the claims are to be embraced within their scope.