the invention is describe below with reference to drawings . these drawings illustrate certain details of specific embodiments that implement the systems , methods , and computer program products of the present invention . however , describing the invention with drawings should not be construed as imposing , on the invention , any limitations that may be present in the drawings . for example , the embodiments that follow describe the present invention in the context of web pages usually accessed over the internet . nevertheless , the scope of the present invention is not limited to electronic content formatted as web pages nor is it limited to content that is ordinarily accessed through the internet . the present invention relates to methods , systems , and computer program products for providing an audio interface to electronic content . two embodiments are described below . each embodiment is a significant advance over the prior art because no modification of the content &# 39 ; s source is required . the first embodiment is most useful for content that is arranged as a hierarchical index , with broad topic indices leading to more specific topic indices and eventually to individual documents discussing a particular subject . the present invention creates a hierarchy of categories and indices . a corresponding audio representation allows a client to navigate through the content , where the client need not be a person . for example , the present invention could be accessible to other services needing a voice interface to electronic content . upon reaching the bottom level in the index hierarchy , selection of a link leads to specific documents . reaching specific documents introduces the operation of the second embodiment . here , the present invention identifies the number of links and provides the user with an audio representation of the document text . a client may also choose to hear the links to navigate among various documents . depending on the initial page identified by a client , the present invention may begin operating according to either of these two embodiments . each embodiment includes the benefits of providing an audio interface to dynamic web content without requiring providers to modify their documents . the embodiments of the present invention may comprise a special purpose or general - purpose computer comprising various computer hardware . other embodiments within the scope of the present invention also include computer - readable media having computer - executable instructions or data structures stored thereon . such computer - readable media can be any available media that can be accessed by a general - purpose or special - purpose computer . by way of example , and not limitation , such computer - readable media can comprise ram , rom , eeprom , cd - rom or other optical disk storage , magnetic disk storage or other magnetic storage devices , or any other medium which can be used to store the desired executable instructions or data structures and which can be accessed by a general - purpose or special - purpose computer . when information is transferred or provided over a network or other communications connection to a computer , the computer properly views the connection as a computer - readable medium . thus , such a connection is also properly termed a computer - readable medium . combinations of the above should also be included within the scope of computer - readable media . computer - executable instructions comprise , for example , instructions and data which cause a general - purpose computer , special - purpose computer , or special - purpose processing device to perform a certain function or group of functions . the computer - executable instructions and associated data structures represent an example of program code means for executing the steps of the invention disclosed herein . the invention will be described in the general context of computer - executable instructions , such as program modules , being executed by a computer . generally , program modules include routines , programs , objects , components , data structures , or the like that perform particular tasks or implement particular abstract data types . moreover , those skilled in the art will appreciate that the invention may be practiced with other computer system configurations , including hand - held devices , multi - processor systems , microprocessor - based or programmable consumer electronics , network pcs , minicomputers , mainframe computers , and the like . the invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network . in a distributed computing environment , program modules may be located in both local and remote memory storage devices . turning now to fig3 an environment , including the present invention , for accessing electronic content is referenced generally as 300 . html source 310 is an example of electronic content that is common to the web . however , the invention imposes no particular requirement on the format of the content &# 39 ; s source or on how the content typically is accessed . visual browser 320 accesses html source 310 and provides a visual representation for monitor 330 . visual browsers , such as microsoft &# 39 ; s internet explorer and netscape &# 39 ; s navigator are both well known in the art . voice browser 340 provides an audio interface to html source 310 that is suitable for use by telephone 350 . alternatively , voice browser 340 could be used in conjunction with visual browser 320 to provide simultaneous visual and audio interfaces . similarly , visual browser 320 could also be specialized to generate content that would be suitable for the limited space of a telephone display . then , visual browser 320 and voice browser 340 could be used simultaneously through telephone 350 . fig4 shows some of the basic components that make up voice browser 340 . in addition to the following relatively brief treatment , the operation of these basic components will be described in greater detail with respect to the flow chart of fig5 . line / call manager 410 is responsible for establishing and maintaining telephone connections . text to speech 420 converts the text it receives to speech that can be communicated to a client and is an example of processor means for generating an audio representation of electronic content . text to speech 420 may also include some prerecorded speech . for example , prerecorded speech could be used for frequently used words , links , text or prompts . modules for implementing both line / call manager 410 and text to speech 420 are well known in their respective arts . document parsing and audio layout 430 receives electronic content and identifies any text and links included within the electronic content and is an example of processor means for parsing electronic documents . ( links are content elements that lead to other locations in the same document or to other documents entirely . html links , for example , create locations within a document &# 39 ; s visual representation that may be selected to further explore the link &# 39 ; s subject , such a defining a word or leading to related material .) the audio layout portion may organize certain content into a hierarchy as an aid to navigation and is an example of processor means for mapping any text and links identified into one or more categories . speech recognition 440 interprets the audio or voice data received from a client so that command processing 450 can execute the client &# 39 ; s request . speech recognition 440 is an example of processor means for receiving a spoken instruction from a client . modules for implementing speech recognition 440 are well known in the respective art . command processing 450 may also perform various general control functions and coordinate the operation of other components . document retrieval protocols 460 request and receive the electronic content of interest and are examples of processor means for obtaining electronic documents and for following links . these document retrieval protocols 460 are also well known in the art of accessing electronic content , especially in the context of html documents . as described in fig3 and 4 , voice browser 340 provides an audio interface without imposing the limitations found in prior art solutions . specifically , voice browser 340 does not require content providers to modify their documents to support a voice interface . therefore , the dynamic content of the web is available to voice brower 340 at the same instant it is available to visual brower 320 . how voice browser 340 operates to create an audio interface is described more fully with reference to fig5 . all acts shown in the flow chart of fig5 will be described by using the document shown generally in fig6 and more specifically in fig7 - 9 . because each figure number is incorporated into individual references , i . e ., reference 650 appears in fig6 and reference 940 appears in fig9 the specific figure number may be inferred and therefore may not be explicitly identified in the discussion that follows . it should also be noted that while the steps of fig5 are shown sequentially , there is no requirement that one step be completed prior to the next step beginning . for example , the prompts can be interrupted or anticipated by making a selection before the prompt finishes or before it even begins . fig6 is an example of content that provides hierarchical indices leading to more textually oriented material and is suitable for enhanced mapping . in step 510 , a particular document is identified or selected . for example , text to speech 420 may prompt the client to select or request a desired source of information . options include unified messaging , home page , favorites , etc . prompts for unified messaging , home page , favorites , etc ., are examples prompts that may be prerecorded and included in text to speech 420 . in response , the client selects the personal home page shown in fig6 . the present invention can also include a variety of global spoken navigation commands , such as fast forward , rewind , cancel , forward , back , home , links , fax , telephone , and email . fax , telephone , and email are instructions to fax , telephone ( voice mail ), or email the current document &# 39 ; s contents , or some portion thereof , in audio and / or visual form based on what is appropriate for the particular instruction given , to someone selected from the client &# 39 ; s contact list ; the other terms retain their ordinary meaning . for example , an instruction to fax would send a visual representation of at least a portion of the document &# 39 ; s contents to the fax recipient . links is a request to hear a page &# 39 ; s links only rather than its text . next , in step 520 , document retrieval protocols 460 retrieve or obtain the document . no particular protocols are imposed according to the present invention . for example , the document may be stored locally , stored on a local area network , stored on a private wide area network , or stored on the internet . the document shown in fig6 is retrieved from the internet . having obtained the requested document , in step 530 document parsing & amp ; audio layout 430 next parses the content to identify any title , any text , any links , and any link names included within the document . a link name is simply the text that forms the link . for example , “ weather ” is the link name of weather category 810 . parsing the retrieved document to identify title , text , links , and link names that may be present illustrates how an audio interface may be provided without requiring changes to the document source . in conjunction with the other aspects of the present invention , this allows immediate audio access to dynamic visual content that otherwise would be unavailable in the prior art . once parsed , in step 540 the text and links included within the document are mapped to various categories . fig6 identifies the categories present in the selected document and also shows some portions of the document that are filtered out and ignored . top banner 610 and bottom banner 660 include a variety of images and other content that is not particularly suitable for voice interaction . however , the enhanced mapping identifies three categories of information stored on the page , portfolios 630 , weather 640 , and headlines 650 . each of the categories may also include content that is ignored . for example , graphic 840 ( see fig8 ) is eliminated because there is no speech analog , although alternate information provided within the image tag , such as the text of the “ alt ” attribute , could be used . search fields and instructions 770 and 850 ( see fig7 & amp ; 8 ) are eliminated because it is impractical to enter this type of data by speaking into a telephone . there are a variety of ways to identify the page content that should be mapped . for example , it may be possible to use html tags , including attributes , as an indication of various categories . the enhanced mapping feature of the present invention for my yahoo ! pages looks for a tag with a particular background color attribute . other mappings may use other html tags and / or tag attributes to identify categories . while enhanced mapping beyond the default mapping provided by parsing text and links requires some degree of customization , a single mapping can be used for all corresponding pages provided by a site . thus , a single my yahoo ! enhanced mapping provides enhanced mapping for all my yahoo ! pages . fig1 shows the hierarchy created by enhanced mapping of the document shown in fig6 . the categories 1010 include portfolios 710 , weather 810 , and my front page headlines 910 . the first - level of links 1020 includes quotes 720 within the portfolios 710 category , salt lake city , utah 820 within the weather 810 category , and top stories from reuters 920 , tech news from news . com 930 , and top sport stories from ap 940 within the my front page headlines 910 category . the second - level of links 1030 includes djia 730 and nasdaq 750 within the quotes 720 first - level of portfolios 710 and the individual story headlines 922 - 926 , 932 - 936 , 942 - 946 within the first - level links top stories from reuters 920 , tech news from news . com 930 , and top sport stories from ap 940 all within the my front page headlines 910 category . the text of stories 1040 are documents that are produced by selecting any of the second - level links 1030 . in step 550 , text to speech 420 generates the audio representation that corresponds to the document . it is not necessary that all of the audio representation be generated at one time . for example , a portion of the audio may be generated and communicated to the client while another portion is being generated . the audio may also be generated on demand as each level in the mapped hierarchy is accessed . next , in steps 560 - 590 , text to speech 420 prompts the client to make various selections from categories 1010 , first - level links 1020 , and second - level links 1030 to reach text of stories 1040 . again , some of these prompts may be prerecorded . because each of the categories shown in fig7 - 9 includes options that may not be relevant to or available in other categories , steps 560 - 590 will be discussed separately for fig7 fig8 and fig9 . thus , steps 560 - 590 represent all possible choices . for certain documents , some of the steps may not be required . the foregoing description presumes that the selections made in steps 560 - 580 do not result in a document that is mapped . assuming that a client chooses portfolios 710 in response to the category selection prompt in step 560 , the following will occur . because portfolios 710 includes only a single first - level link , quotes 710 , prompting in step 570 is skipped , but the text of quotes 710 played , and the client will be prompted to select a second - level link , either djia 730 or nasdaq 750 ( i . e ., “ quotes , please choose from djia or nasdaq ”). in step 590 , choosing djia 730 will play audio of text 740 and choosing nasdaq 750 will play audio of text 760 . however , djia 730 and nasdaq 750 are also links . although choosing the links global command would not alter the choices offered , it would alter the action taken by making a selection . in this case choosing djia 730 or nasdaq 750 would follow the respective links rather than playing the audio representation of text 740 or text 760 . selecting weather 810 at step 560 similarly leads to skipped steps . however , in this case , both steps 570 and steps 580 are skipped because salt lake city , utah 820 is the only first - level link and there are no second - level links . therefore , selecting weather 810 will result in the audio representation of text 830 being played ( i . e ., “ salt lake city , utah , 49 to 82 f ”) at step 590 . a links command could also be issued here to identify salt lake city , utah 820 , but the link would only be followed if the client explicitly selected it . in contrast , selecting my front page headlines 910 at step 560 does not result in any skipped steps . in step 570 , the client will be prompted to select from the first - level links top stories from reuters 920 , tech news from news . com 930 , and top sports stories from ap 940 . selecting any of these first - level links in step 570 will result in step 580 prompting for the stories associated with the first - level link . for example , selecting top sport stories from ap 940 in step 570 will lead to step 580 prompting the client to select from nl playoffs notebook 942 , nfl roundup 944 , and america &# 39 ; s cup enters third day 946 . in step 590 , an audio representation of the document text corresponding to the selection made in step 580 will be played to the client . portfolios 710 , weather 810 , and my front page headlines 910 present a large amount of information to the client . as the client moves from one category to another , each category presents an increasing number of links or options . in a visual environment , it is a relatively simple matter for the client to scan a page and remember the links or options that are currently available . however , in an audio representation , it is significantly more difficult to keep the links and options of one page separate from the links and options of another page . therefore , one aspect of the present invention accumulates all links and options from certain pages that are visited and makes the accumulated links and options of a previously visited page available in a subsequent page . accumulation is desirable because “ pages ” are a visual motif that does not necessarily carry over into an audio representation . particularly in a personal home page environment , a client may view the personal home page as simply a monolithic source of information . someone familiar with the available content who is moving between various levels in the hierarchy , may find an explicit requirement of returning to a particular page , for the sole purpose of selecting a link or other option from that page , cumbersome or even annoying . therefore , accumulation preserves the organizational benefits of hierarchical organization - the client continues to be informed regarding the content of a particular page - without limiting the availability of links to only those present on the particular page . for example , selecting the nl playoffs notebook 942 link of top sport stories from ap 940 found in the category my front page headlines 910 , will lead to the nl playoffs notebook document . that document contains both text and links that are available to the client . in a typical visual browser , if the client next wanted to choose category weather 810 , the user would need to return to web page 600 first . however , the present invention , by accumulating links , would allow the client to select weather 810 from the nl playoffs notebook document since web page 600 had been previously visited . in a preferred embodiment , accumulation is limited to certain predetermined web content that would benefit from the feature , such as personal home pages . in contrast to fig5 fig1 is a flow chart illustrating the operation of a preferred embodiment of the present invention that provides only the default mapping of separating text and links . in step 1110 , a client selects the option of starting with a list of favorite internet sites . text to speech 420 prompts the user to select one of the sites listed , step 1120 . as before , in step 1130 the document is retrieved using the protocols that are appropriate given the document &# 39 ; s location . again , as before , the content is parsed in step 1140 to identify any title , any links , any link names , and any text included in the document . fig1 is an example of electronic content 1200 that is useful in describing the embodiment disclosed in fig1 . parsing step 1140 identifies title 1240 ( html titles are indicated by explicit tags ), links and corresponding link names 1210 , 1220 , and 1230 , as well as the document text . with these various elements identified , audio representation of electronic content 1200 is generated in step 1150 . once generated , the document title is reported in step 1160 and is followed by reporting the number of links in step 1170 . just as with the description of fig5 parsing the retrieved document to identify any title , any text , any links , and any corresponding link names that may be present shows how an audio interface may be provided without requiring changes to the document source . together with the other aspect of the present invention , this provides immediate audio access to dynamic , visually - oriented , content that otherwise would be inaccessible to the prior art . in the case of the electronic content 1200 , the present invention reports the document title as guide to filing a utility patent application 1240 . there are three links , named u . s . patent and trademark office 1210 , www . uspto . gov 1220 , and patent and trademark depository library 1230 . then , in step 1180 , an audio representation of the electronic document &# 39 ; s text is played for or communicated to the user . in the case of electronic content 1200 , this text includes everything except the title 1240 . the client may also choose the global links command , to hear an audio representation of the three links , 1210 , 1220 , and 1230 . by choosing a link , the client instructs the present invention to follow the link , as in step 1120 , beginning audio interface process anew at step 1130 . the present invention may be embodied in other forms without departing from its spirit or essential characteristics . as properly understood , the preceding description of specific embodiments is illustrative only and in no way restrictive . for example , using web pages accessible over the internet to describe the present invention does not limit the invention to any specific format of electronic content or any particular means of accessing electronic content . the scope of the invention is , therefore , indicated by the appended claims as follows .