WO2002027520A1

WO2002027520A1 - Segmenting electronic documents for use on a device of limited capability

Info

Publication number: WO2002027520A1
Application number: PCT/US2001/030465
Authority: WO
Inventors: Richard D. Romero; Adam L. Berger
Original assignee: Eizel Technologies, Inc.
Priority date: 2000-09-27
Filing date: 2001-09-27
Publication date: 2002-04-04
Also published as: KR20080067022A; CA2423695A1; EP1320806A1; JP2004510253A; JP2004510251A; CA2423611C; AU2001294881A1; CA2423611A1; WO2002027516A9; EP1330723A4; KR100855997B1; EP1320806A4; WO2002027520A9; KR20030045086A; KR100903528B1; AU2001294884A1; EP1330723A1; KR20030060899A; WO2002027516A1

Abstract

A method includes receiving a machine readable file containing a document (12) that is to be served to a client (10) for display on a client device (10), the organization of each of the document (12) in the file being expressed as a hierarchy of information, and deriving subdocuments (1) from the hierarchy of the information, each of the subdocuments (1) being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments (1) containing information that enables it to be linked to another one of the subdocuments (1).

Description

SEGMENTING ELECTRONIC DOCUMENTS FOR USE ON A DEVICE OF LIMITED CAPABILITY

This patent application has the benefit of the filing date of United States Provisional Applications 60/238,424 filed on October 10, 2000, and 60/235,551, filed on September 27, 2000, both incorporated by reference. BACKGROUND

This invention relates to segmenting, transforming, and viewing electronic documents.

People often access electronic documents such as web pages, text files, email, and enterprise (proprietary corporate) data using desktop or laptop computers that have display screens that are larger than 10 inches diagonally and using connections to the Internet that have a communication rate of at least 28.8kbps. Electronic documents are typically designed for transmission to and rendering on such devices.

Internet-enabled devices like mobile phones, hand-held devices (PDAs), pagers, set-top boxes, and dashboard-mounted microbrowsers often have smaller screen sizes, (e.g., as little as two or three inches diagonally across), relatively low communication rates on wireless networks, and small memories. Some of these devices cannot render any part of a document whose size exceeds a fixed limit, while others may truncate a document after a prescribed length. Accessing electronic documents (which often contain many paragraphs of text, complex images, and even rich media content) can be unwieldy or impossible using these devices.

Automatic content transformation systems convert electronic documents originally designed for transmission to and rendering on large-screen devices into versions suitable for transmission to and rendering on small-display, less powerful devices such as mobile phones. See, for example, Wei-Ying Ma, Ilja Bedner, Grace Chang, Allan Kuchinsky, and HongJiang Zhang. A Framework for Adaptive Content Delivery in Heterogeneous Network Environments, of SPIE Multimedia Computing and Networking 2000. San Jose, CA, January, 2000. SUMMARY

In general, in one aspect, the invention features a method that includes receiving a machine readable file containing a document that is to be served to a client for display on a client device, the organization of each of the documents in the file being expressed as a hierarchy of information, and deriving subdocuments from the hierarchy of information, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments. Implementations of the invention may include one or more of the following features. The language is extensible mark-up language (XML). The deriving includes traversing the hierarchy and assembling the subdocuments from segments, at least some of the subdocuments each being assembled from more than one of the segments. The assembling conforms to an algorithm that tends to balance the respective sizes of the subdocuments or that tends to favor assembling each of the subdocuments from segments that have common parents in the hierarchy or that conforms to an algorithm that tends to favor assembling each of the subdocuments from segments for which replications of nodes in the hierarchy is not required. The file is received from an origin server associated with the file. The file is expressed in a language that does not organize segments of the document in a hierarchy, and the deriving of subdocuments includes first converting the file to a language that organizes segments of the document in a hierarchy. The subdocuments are served to the client individually as requested by the client. The subdocuments are served to the client using a hypertext transmission protocol. The subdocuments are requested by the client based on the contained information that enables a subdocument to be linked to another of the subdocuments.

A portion of the document is identified that is to be displayed separately from the rest of the document. When the subdocument in which the portion would otherwise have appeared is served to the client device, a graphical device is embedded that can be invoked by the user to retrieve the subdocument that includes the portion of the document that is to be displayed separately.

In general, in another aspect, the invention features a machine-readable document held on a storage medium for serving to a client, the document being organized as a set of subdocuments, each of the subdocuments containing information that enables the subdocument to be linked to another of the subdocuments, each of the subdocuments comprising an assembly of segments of the document that are part of a hierarchical expression of the document, the subdocuments being of approximately the same size.

Implementations of the invention may include one or more of the following features. The information that enables the subdocument to be linked includes a URL. The hierarchical expression includes extensible markup language (XML).

In general, in another aspect, the invention features receiving from a client a request for a document to be displayed on a client device, serving separately to the client a subdocument that represents less than all of the requested document, each subdocument containing information that links it to at least one other subdocument, receiving from the client an invocation of the link to the other subdocument, and serving separately to the client device the other subdocument.

Implementations of the invention may include one or more of the following features. The subdocuments are served to the client using a hypertext transmission protocol. The subdocuments are of essentially the same length. The subdocuments are of a length that can be displayed on the client device without further truncation.

In general, in another aspect, the invention features a method that includes receiving from a server at a client device, a subdocument of a larger document for display on the client device, displaying the subdocument on the client device, receiving at the client device a request of a user to have displayed another subdocument of the larger document, receiving separately from the server at the client device, the other subdocument, and displaying the other subdocument on the client device, the subdocuments being of substantially the same length. Implementations of the invention may include one or more of the following features. All of each of the subdocuments is displayed at one time on the client device, or less than all of each of the subdocuments is displayed on the client device at one time. In general, in another aspect, the invention features a method that includes displaying a subdocument of a document on a client device, displaying an icon with the subdocument, and in response to invocation of the icon, fetching another subdocument of the document from a server and displaying the other subdocument on the client device, each of the subdocuments being less than the entire document, the subdocuments being of approximately the same size. Implementations of the invention may include one or more of the following features. An indication is given of the position of the currently displayed subdocument in a series of subdocuments that make up the document. The indication includes the total number of subdocuments in the series and the position of the currently displayed document in the sequence. The subdocuments are derived from the document at the time of a request from the client device for the document. The subdocuments are derived in a manner that is based on characteristics of the client device. The characteristics of the client device are provided by the client in connection with the request. The characteristics include the display capabilities and memory constraints of the client device. The subdocuments are derived from the document before the client requests the document from the server. The subdocuments are derived for different documents from different origin servers. The subdocuments are derived from the document at a wireless communication gateway.

In general, in another aspect, the invention features apparatus that includes a network server configured to receive a machine readable file containing a document that is to be served to a client for display on a client device, and to derive subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments.

In general, in another aspect, the invention features apparatus including comprising means for receiving a machine readable file containing a document that is to be served to a client for display on a client device, and means for deriving subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments. In general, in another aspect, the invention features a machine-readable program stored on a machine-readable medium and capable of configuring a machine to receive a machine readable file containing a document that is to be served to a client for display on a client device, and derive subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments

Other advantages and features will become apparent from the following description, and from the claims. DESCRIPTION

(Figure 1 shows a document transforming and serving system.

Figure 2 shows a document.

Figure 3 shows a flow diagram.

Figures 4 and 5 show document hierarchies.

Figure 6 shows a process for document transformation. Figure 7 shows a database.

Figure 8 shows a document transformation system.

Figure 9 shows a process for expressing preferences.

Figure 10 shows a preference form. Figures 11 and 12 show preference forms. Figure 12 shows a wireless/wired communication system. Figure 13 shows a document transformation system. Figure 14 shows a web page. Figures 15 and 16 show small-screen displays of portions of a web page. Figure 17 shows isolating subdocuments for separate use.)

In various implementations of the invention, electronic documents are segmented and transformed before being served through low bandwidth communication channels for viewing on user devices that have small displays and/or small memories. We discuss the segmentation feature first and then the transformation feature. SEGMENTATION

At a high level, as shown in figure 1, when a user of an Internet-enabled device 10 (a WAP-enabled mobile phone, for example) requests an electronic document 12 (e.g., a web page, an email, a text file, or a document in a proprietary format or markup language), the user's request, expressed in a URL, eventually makes its way to a proxy server 14. The proxy server then requests the document from an origin server 16 using the URL. The origin server is a computer on the Internet responsible for the document. After receiving the document from the origin server in the form of a web page, the proxy server breaks (segments) the document into subdocuments. The proxy server transmits the first of these subdocuments 1 to the client as a web page. The segmenting of the document need not be done in the proxy server but can be done in other places in the network, as described later.

As shown in figure 2, each of the subdocuments 20 delivered by the proxy server to the client contains hyperlinks 22, 24 to the next and previous (each where applicable) subdocuments in the series. The hyperlinks are displayed to the user. Ifthe user selects a forward-pointing (or backward-pointing) hyperlink from a subdocument, that request is transmitted to the proxy server, which responds with the next (or previous) subdocument. As shown in figure 3, the first step of the segmentation process is to determine (30) the maximum document size permissible by the client device. Ifthe client-server communication adheres to the HTTP protocol standards as described in RFC2616 (R. Fielding et al., RFC 2616: Hypertext Transfer Protocol - HTTP/1J. June, 1999. **http://www. w3.org/Protocols/rfc2616/rfc2616.txt**.), the client advertises information about itself to the proxy server within the header information sent in the HTTP request. The server can use, for instance, the value of the USER- AGENT field to determine the type of microbrowser installed on the client device and, from this information, determine the maximum document size by consulting a table listing the maximum document size for all known devices.

We will denote the length of the original document by N. One can measure length by the size of the document (including markup) in bytes. We denote the maximum permissible length of a document allowed by the client as M. Clearly, any segmentation algorithm that respects the client-imposed maximum length of M must generate from a length-N document at least ceil(N/M) segments.

The next step of the segmentation process is to convert the input document into XML (32), a markup language whose tags imply a hierarchical tree structure on the document. An example of such a tree structure is shown in figure 4. Conversion to XML from many different source formats, including HTML, can be done using existing software packages.

As shown in figure 4, the third step is to apply a procedure to divide (34) the XML tree 40 into segments, each of whose length is not greater than M. The leaves 42 of the tree represent elements of the original document — ext blocks, images, and so on. Internal nodes 44 of the tree represent structural and markup information — markers denoting paragraphs, tables, hyperlinked text, regions of bold text, and so on. One strategy for accomplishing the segmentation task is to use an agglomerative, bottom-up leaf-clustering algorithm. The leaf-clustering approach begins by placing each leaf in its own segment (as shown in figure 4) and then iteratively merging segments until there exists no adjacent pair of segments that should be merged. Figure 5 shows the same tree after two merges have occurred, leaving merged segments 50, 52.

Each merging operation generates a new, modified tree, with one fewer segments. Each step considers all adjacent pairs of segments, and merges the pair that is optimal according to a scoring function defined on candidate merges. An example scoring function is described below. When the algorithm terminates, the final segments represent partitions of the original XML tree. SCORING FUNCTION

In one example scoring function, a lower score represents a more desirable merge. (In this context, one can think of "score" of a merge as the cost of performing the merge.) In this example, the score of merging segments x and y is related to the following quantities:

1. The size of the segments: The scoring function should favor merging smaller segments, rather than larger ones. Let |x| denote the number of bytes in segment x. All else being equal, if |x|=100, |y|=150, and |z|=25, then a good scoring function causes score(x,z) < score(y,z) < score(x,y). The effect of this criterion, in practice, is to balance the sizes of the resulting partitions.

2. The familial proximity of the segments: All else being equal, if segments x and y have a common parent z, then they comprise a more desirable merge than if they are related only through a grandparent (or more remote ancestor) node. That two segments are related only through a distant ancestor is less compelling evidence that the segments belong together than if they are related through a less distant ancestor.

3. The node replication required by the merge: Internal nodes may have to be replicated when converting segments into well-formed documents. Of course, in partitioning an original document into subdocuments, one would like to minimize redundancy in the resulting subdocuments. Defining by d(x,y) the least number of nodes one must travel through the tree from segment x to segment y, and by r(x,y) the amount of node replication required by merging segments x and y. A general candidate scoring function is then score(x,y) = A(|x|+|y|) + B(dx,y) + C(rx,y), where A and B and C are functions (for example, real coefficients) which can be set by the user. For example:

Algorithm 1: Δgglomerative segmentation of an XML document Input: D: XML document M: maximum permissible subdocument length

Output: D': XML document with no less than ceil(N M) leaves, each with a size no larger than M.

1. Assign each leaf in D to its own segment

2. Score all adjacent pairs of segments i, x₂ in D with score (xι,x₂)

3. Let x,y be the segment pair for which score(x,y) is minimal 4. If merging x and y would create a segment of size >M, then end

5. Merge segments x and y

6. Go to step 1

Other strategies could be used for scoring candidate segment merges. The algorithm just described takes no account of the actual lexical content of the document when deciding how to segment. Other examples use a criterion that takes into account the identities of the words contained in each segment and favors locations where a break does not appear to disrupt the flow of information. To accomplish this, a system must examine the words contained in the two segments under consideration for merging to determine if they pertain to the same topic. Such "text segmentation" issues are addressed, for instance, by automatic computer programs such as the one described in M. Hearst, TextTiling: Segmenting text into multi-paragraph subtopic passages. Computational Linguistics 23(1) 33-65, 1997. TextTiling is an algorithm designed to find optimal locations to place dividers within text sources. Returning to figure 3, the next step is to convert the segments of the final tree into individual, well-formed XML documents (36). Doing so may require replication of nodes. For instance, in Figure 5, merging leaves B and F has the effect of separating the siblings F and G. This means that when converting the first and second segments of the tree on the right into well-formed documents, each document must contain an instance of node C. In other words, node C is duplicated in the set of resulting subdocuments. The duplication disadvantage would have been more severe if nodes F and G were related not by a common parent, but by a common grandparent, because then both the parent and grandparent nodes would have to be replicated in both segments. After having computed a segmentation for the source document, the proxy server stores the individual subdocuments in a cache or database (38) to expedite future interaction with the user. When the user follows a hyperlink on the first subdocument to access the next subdocument in the sequence, the request is forwarded to the proxy server, which responds (39) with the appropriate subdocument, now stored in its cache. Ifthe proxy server is responsible for handling requests from many different clients, the proxy server maintains state (41) for each client to track which document the client is traversing and the constituent subdocuments of that document. As before, the proxy server can use the HTTP header information — this time to determine a unique identification (IP address, for example, or a phone number for a mobile phone) for the client device, and use this code as a key in its internal database, which associates a state with each user. A sample excerpt from such a database appears below:

Many client devices cannot process documents written in XML and can process only documents written in another markup language, such as text, HTML, WML or HDML. Translation of the XML subdocuments to the other format (43) could be done at the proxy server by any available translator.

The agglomerative segmentation algorithm (Algorithm 1, above) is performed only once per source document, at the time the user first requests the document. As the user traverses the subdocuments comprising the source document, the computational burden for the proxy server is minimal; all that is required is to deliver the appropriate, already-stored subdocument.

Once the segmentation of a document into subdocuments has been achieved, it is possible to use the subdocuments in a variety of ways other than simply serving them in the order in which they appear in the original document.

For example, as shown in figure 17, an original HTLM document 100 may contain a form 102. In order to make the user's interaction with the page sensible, it may be useful to separate the form from the rest of the page and replace it with a link in one of the subdocuments. Then the user can invoke the link on his local device to have the form presented to him. If he prefers not to see or use the form, he can proceed to navigate through the other subdocuments as discussed earlier without ever getting the form. For this purpose, the documented can be segmented into subdocuments 104, 106, and 108 that represent parts of the main body of the document and subdocuments 110, 112 that represent portions of the form 102. One of the subdocuments 106 contains an icon 114 that represents a link 116 to the form. Other links 118, 120, and 122 permit navigation among the subdocuments as described earlier. TRANSFORMATION

The content of the subdocuments that are served to the user devices can be automatically transformed in ways that reduce the amount of data that must be communicated and displayed without rendering the information represented by the data unusable. Users can customize this automatic transformation of electronic documents by expressing their preferences about desired results of the transformation. Their preferences are stored for later use in automatic customized transformation of requested documents. For example, a user may wish to have words in original documents abbreviated when viewing the documents on a size-constrained display. Other users may find the abbreviation of words distracting and may be willing to accept the longer documents that result when abbreviations are not used. These preferences can be expressed and stored and then used to control the later transformation of actual documents.

We discuss steps in transforming the documents first and then the process of soliciting user preferences. TRANSFORMING DOCUMENTS

As shown in figures 1 and 6, and as explained earlier, when the user 6 of the device 10 requests (11) the document 12 (e.g., by entering a URL into a browser running on the device, selecting from a bookmark already stored in the browser, or selecting a link from a hypertext document previously loaded into the browser), the proxy server receives the request (18) and fetches (20) the document from the origin server. After receiving the document from the origin server, the proxy computer consults (24) a database 26 of client preferences to determine the appropriate parameters for the transformation process for the device 8 for the user who is making the request. The proxy computer then applies (28) the transformations to the document to tailor it for transmission to (30) and rendering (32) on the client device.

The HTTP header in which the client device advertises information to the proxy server about itself can include two relevant pieces of information:

1. A unique identifier for the device: For example, for wireless Internet devices equipped with a microbrowser distributed by Phone.com, the HTTP header variable X- UP-SUBNO is bound to a unique identifier for the device.

2. The device type: For example, the HTTP header variable USER-AGENT is bound to a string that describes the type of browser software installed on the device.

When document transformation occurs, the proxy computer has already obtained the unique ID and can use it as a key to look up, in the database, a set of preferences associated with the user. Figure 7 shows an example of rows in a fictitious database 24. Each row 40 identifies a device by the device's telephone number. The row associates user preferences (four different ones in the case of figure 7) with the identified device. In this case, the telephone number (e.g., of a mobile phone) is the unique ID that serves as the key for the records in the database.

Having consulted the database to determine the appropriate preference values for this user, the proxy computer can use these values to guide its transformation process. Thus, as shown in figures 1 and 4, the inputs to the transformation process are a source document (in HTML, for instance) and a set of user preference values (one row in the database from figure 6)

As shown in figure 8, document transformation includes a sequence of operations, such as date compression 52, word abbreviation 54, and image suppression 55, in converting an original document to a form more suitable for rendering on a small-display device. At every step, the preferences for the target device are used to configure the transformation operations. For instance, the client-specific preferences could indicate that word abbreviation should be suppressed, or that image suppression 55 should only be applied to images exceeding a specified size.

In addition to being suppressed, images can be subjected to other kinds of transformations to reduce their size. For example, images may be compressed, downsampled, or converted from color to black and white.

Examples of user-configurable parameters include the following: Abbreviations

To reduce the space required to display a document, words may be abbreviated. There are many strategies for compressing words, such as truncating long words, abbreviating common suffices ("national" becomes "natT), removing vowels or using a somewhat more sophisticated procedure like the Soundex algorithm (Margaret K. Odell and Robert C. Russell, United States Patents 1,261,167 (1918) and 1,435,663 (1922).). The corresponding user-configurable parameter would be a Boolean value indicating whether the user wishes to enable or disable abbreviations. Enabling abbreviations reduces the length of the resulting document, but may also obfuscate the meaning of the document. Suppression of images

Many small-screen mobile devices are incapable of rendering bitmapped images. Even when possible, rendering of large images may require lengthy transmission times. Bitmapped images are likely to degrade in quality when rendered on low-resolution screens. For these reasons, users may control whether and which kinds of bitmapped images are rendered on their devices. The corresponding user-configurable parameter in this case could be, for instance, a Boolean value (render or do not render) or a maximum acceptable size in pixels for the source image. Entity compression

A transformation system can employ a natural language parser to detect and rewrite certain classes of strings into shorter forms. For instance, a parser could detect and rewrite dates into a shorter form, so that, for instance, "December 12, 1984" becomes " 12/12/84", "February 4" becomes "2/4", and "The seventh of August" becomes "8/7". The corresponding user-selectable parameter value could be a Boolean value (compress or do not compress), or it could take on one of three values: do not compress, compress into month/day/year format, or compress into day/month/year format.

Similarly, a transformation system could parse and compress numeric quantities, so that (for instance) "seventeen" becomes "17" and "ten gigabytes" becomes "10GB." A wide variety of other transformation could be devised for a wide variety of types of documents. SPECIFYING AND STORING PER-DEVICE PREFERENCES

We return now to discuss two example methods for acquiring preferences from device users and for associating these preferences with specific client devices. Entering preferences from the small-display device

A user can enter and maintain preferences by visiting the proxy computer using the same small-display device he uses for Internet access. As shown in figure 9, the proxy computer could store a hypertext form 60 that users of small-display devices retrieve and fill in according to their preferences. Upon receiving an HTTP request 62 from a client device, the proxy computer will automatically (using the HTTP protocol) obtain the unique identifier for the client device. The proxy computer then transmits to the user a form 64 that contains a set of preferences. Ifthe client device already has an associated entry in the database, the current value for each parameter can be displayed in the form; otherwise, a default value will be displayed. The user may change parameters on this form as he sees fit and then submit the form back 66 to the proxy computer, which stores the updated values in the database in the record associated with that client device.

Entering preferences from a conventional computer

Alternatively, the user can visit the same URL using a conventional web browser on a desktop or laptop computer. The proxy computer will be unable to determine automatically from the HTTP header information which device to associate the preferences with. The user must explicitly specify the unique identifier — phone number, for instance — of the device for which the user wishes to set the preferences.

Figure 10 shows an example of the form appearing on a conventional HTML-based desktop web browser. Figure 11 shows the first screen of the corresponding page appearing on a four-line mobile phone display (A user must scroll down to see the rest of the options.)

SPECIFYING AND STORING PER-TYPE PREFERENCES

In the previous discussion, the user is a person accessing a remotely-stored document using a small-screen device, and a proxy computer (which performs the transformations) mediates between the user's device and the Internet as a whole. Another setting in which configurable transformations are useful is for an individual or institution to exercise control over the appearance on small-display devices of documents that it generates. To that end, the origin server responsible for storing and transmitting the data can be equipped with automatic content transformation software (using a module or "plug-in" for the web server software). The origin server host can then configure and control the transformation software as desired.

The origin server may also offer to an author of content an ability to configure transformations once for any user retrieving documents from that server for a particular type of client device. In other words, instead of offering the end user the ability to customize the transformations, one can instead offer this ability to the person or institution that authored the content. This scenario is relevant when the content provider desires strict control over the appearance of their content on small-display devices. Rather than storing a database of user (individual device) preferences, then, the origin server stores only a single set of parameter values for the transformation for each type of device. The information flow from user to origin server is thus:

1. User requests a document from origin server.

2. Origin server receives the request and information on the type of client device making the request.

3. Origin server consults the transformation parameters appropriate for that device in processing the requested document.

4. Origin server delivers the transformed document to the client device.

An example of the entries in the database that are used for step 3 is shown below:

The previous section described a method for end users to specify and store preferences, to be associated with a single device. This section described a method for content creators to configure the transformation of documents delivered from their origin server. These two scenarios are not incompatible. Imagine that an end user requests a document X from an origin server Y. Imagine further that the end user has registered a set of preferences for his transformations, and that there exists on the origin server a separate set of preferences for documents delivered from that origin server. The document will be transformed first according to the preferences in the origin server, and then according to the end user's preferences. In this scenario, the end user's preferences sometimes cannot be honored. For instance, ifthe end user does not want words abbreviated, but the preferences for the origin server specify that words are to be abbreviated, then the end user will receive, despite his preferences, a document containing abbreviated words. STORING PREFERENCES ON THE CLIENT DEVICE

An alternative strategy for associating preferences with devices is to use the

HTTP "cookie" state mechanism (D. Kristol and L. Montulli. RFC 2109: HTTP State Management Mechanism. (1997).

**http://www. w3.org/Protocols/rfc2109/rfc2109.txt**). In this case, the preference information is not stored on a database remote from the client device, but rather on the device itself. The information flow of per-device preference information in this setting is as follows:

1. A user of a small-display device submits a request to the proxy computer for the preferences form document. The form document is transmitted from the proxy computer to the device. 2. The user fills in his preferences and submits the filled-in form back to the proxy computer. 3. The proxy computer responds with a confirmation document and also transmits, in the HTTP header information to the client device, a cookie containing that user's preferences. For example, the cookie might look like

Set-Cookie: PREFS- ' abbrevs:yes images:no dates:yes ..."; path=/; expires=04-Sep-01 23:12:40 GMT

4. The client device stores this cookie as persistent state.

5. When a user of the client device subsequently requests a document from the proxy computer, the device also transmits to the proxy computer the cookie containing the stored preferences: Cookie: PREFS- ' abbrevs.yes images:no dates.yes ...";

6. Equipped with the preferences for this client, the proxy computer applies these preferences in transforming the requested document. Ifthe client device did not transmit a cookie, either because the cookie expired or was erased, the proxy computer applies a default transformation. APPLICATIONS

As shown in figure 12, communication between wireless devices 50 and the "wired" Internet 53 typically occur through a gateway 52, which mediates between the wired and wireless worlds. For instance, a request for a document by a user of a WAP- capable device is transmitted to the wireless gateway, which forwards the request to the ^' origin server 54 (on the Internet) responsible (according to the DNS protocol) for the requested document.

Ifthe requested document has been designed specifically for the client device and written in the markup language accepted by the device—sometimes HTML, but more often another markup language such as WML, HDML, or a proprietary language— content transformation isn't necessary. Because different wireless data devices have different capabilities, a content creator would have to create a separate version not only for each target markup language but also for every possible target device. The content provider needs also to understand how to detect the type of client device and create a document optimally formatted for that client.

As shown in figure 13, an automatic content transformation system 70 can automatically compress and reformat documents 72 into formats that are optimal for display on specific target devices. This leaves content creators free to concentrate on writing content rather than on retargeting content for a variety of target devices. The content transformation system intercepts requests from non-traditional client devices, customizes the requested documents for display on the target device 78, and transmits the transformed documents 74 to the client. The content transformation system employs user preferences 76 and device specifications 64 to guide the document transformation process.

Ifthe requested page 72 has been designed specifically for the client device making the request, content transformation isn't necessary. But designing documents for wireless devices is no simple matter. The document must be written in the markup language accepted by the device-sometimes HTML, but more often another markup language such as WML, HDML, or a proprietary language. Because the hundreds of different wireless data devices each have different capabilities 64 , a content creator faces the prospect of creating a separate version not only for each target markup language, but for every possible target device. The content provider also needs to understand how to detect the type of client device and create a document optimally formatted for that client.

By using system 70, which automatically compresses and reformats a document 72 for optimal display on a specific target device, content creators are free to concentrate on their core competency—writing content— and not on retargeting content for a variety of target devices. Once installed, a content transformation system intercepts requests from non-traditional client devices, customizes the requested document for display on the target device, and transmits the transformed document to the client. Content transformation systems can use automatic document segmentation to stage the delivery of large documents to devices incapable of processing large documents in their entirety. The core content transformation component 81 can include the segmentation process described earlier. The XML cache object 84 is where the per-user subdocuments are stored for the segmentation process.

Content transformation is a server-side technology and can naturally be deployed at various locations in the client-origin server channel, anywhere from the wireless gateway to the origin server that holds the original content. The following table lists a few of the places content transformation is applicable.

Figure 14 shows an example input document (a full-size web page) that was divided into five subdocuments. Figure 15 shows the bottom of the fourth subdocument 72, corresponding to the middle of the "Bronx-Whitestone Bridge" section of the original page. The hyperlinks (icons) labeled "prev" 74 and "next" 76 bring a user to the third and fifth subdocuments, respectively, when invoked. Figure 16 shows the beginning of the fifth subdocument 78, which begins where the fourth leaves off. The user can scroll through the subdocument as needed. In some implementations, as shown, the icons 74, 76 are only displayed when the user has scrolled to the beginning or end of the subdocument. In other examples, the icons could be displayed at all times. In figures 15 and 16, the numbers and words in the original have been abbreviated

("one" became "1", "and" became "&") and days of the week have been shortened.

The display of each subdocument also includes a display of the heading 79 of the original document. That heading is included in the subdocument when the subdocument is created from the original document. The display also includes an indication of the total number of subdocuments 87 and the position 89 of the current subdocument in the series of subdocuments that make up the original document.

Other implementations are within the scope of the following claims.

For example, in the user interface, the bottom of each subdocument rendered on the target device can contain a graphical status bar showing where the subdocument lies in the set of subdocuments comprising the original document. For instance, ooxoooo could mean "this is the third of seven subdocuments". Moreover, each of the o's in this status bar could be hyperlinked to that subdocument, enabling the user to randomly access different subdocuments in the document. This can be more efficient than proceeding subdocument by subdocument in order.

Claims

1. A method comprising receiving a machine readable file containing a document that is to be served to a client for display on a client device, the organization of each of the documents in the file being expressed as a hierarchy of information, and deriving subdocuments from the hierarchy of information, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments.

2. The method of claim 1 in which the language comprises extensible mark-up language (XML).

3. The method of claim 1 in which the deriving comprises traversing the hierarchy and assembling the subdocuments from segments, at least some of the subdocuments each being assembled from more than one of the segments.

4. The method of claim 3 in which the assembling conforms to an algorithm that tends to balance the respective sizes of the sub-documents.

5. The method of claim 3 in which the assembling conforms to an algorithm that tends to favor assembling each of the subdocuments from segments that have common parents in the hierarchy.

6. The method of claim 3 in which the assembling conforms to an algorithm that tends to favor assembling each of the subdocuments from segments for which replications of nodes in the hierarchy is not required.

7. The method of claim 1 in which the file is received from an origin server associated with the file.

8. The method of claim 7 in which the file is expressed in a language that does not organize segments of the document in a hierarchy, and the deriving of subdocuments includes first converting the file to a language that organized segments of the document in a hierarchy.

9. The method of claim 1 also including serving the subdocuments to the client individually as requested by the client.

10. The method of claim 9 in which the subdocuments are served to the client using a hypertext transmission protocol.

11. The method of claim 9 in which the subdocuments are requested by the client based on the contained information that enables it to be linked to another of the subdocuments.

12. The method of claim 1 also including identifying a portion of the document that is to be displayed separately from the rest of the document, the portion of the document that is to be displayed separately being excluded from the subdocument in which the portion would otherwise have appeared, the portion of the document that is to be displayed separately being included in at least one corresponding subdocument, and when the subdocument in which the portion would otherwise have appeared is served to the client device, embedding a graphical device that can be invoked by the user to retrieve the subdocument that includes the portion of the document that is to be displayed separately.

13. A method comprising receiving, from an origin server, a machine readable file containing a document that is to be served to a client for display on a client device, the file being expressed in a language that does not organize segments of the document in a hierarchy, converting the file to a language that organizes segments of the document in a hierarchy, traversing the hierarchy and assembling subdocuments from the segments, at least some of the subdocuments each being assembled from more than one of the segments, the assembling conforming to an algorithm that tends to (a) balance the respective sizes of the sub-documents, (b) favor assembling each of the subdocuments from segments that have common parents in the hierarchy, and (c) assembling each of the subdocuments from segments for which replications of nodes in the hierarchy is not required. each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments, and serving the subdocuments to the client individually as requested by the client based on the contained information that enables it to be linked to another of the subdocuments, the serving being done using a hypertext transmission protocol.

14. A machine-readable document held on a storage medium for serving to a client, the document being organized as a set of subdocuments, each of the subdocuments containing information that enables the subdocument to be linked to another of the subdocuments, each of the subdocuments comprising an assembly of segments of the document that are part of a hierarchical expression of the document, the subdocuments being of approximately the same size.

15. The document of claim 14 in which the information that enables the subdocument to be linked comprises a URL.

16. The method of claim 14 in which the hierarchical expression comprises extensible markup language (XML).

17. A method comprising receiving from a client a request for a document to be displayed on a client device, serving separately to the client a subdocument that represents less than all of the requested document, each subdocument containing information that links it to at least one other subdocument, receiving from the client an invocation of the link to the other subdocument, and serving separately to the client device the other subdocument.

18. The method of claim 17 in which the subdocuments are served to the client using a hypertext transmission protocol.

19. The method of claim 17 in which the subdocuments are of essentially the same length.

20. The method of claim 17 in which the subdocuments are of a length that can be displayed on the client device without further truncation.

21. A method comprising receiving from a server at a client device, a subdocument of a larger document for display on the client device, displaying the subdocument on the client device, receiving at the client device a request of a user to have displayed another subdocument of the larger document, receiving separately from the server at the client device, the other subdocument, and displaying the other subdocument on the client device, the subdocuments being of substantially the same length.

22. The method of claim 21 in which the subdocuments are expressed in a hypertext transmission protocol.

23. The method of claim 21 in which the request of the user is expressed as a URL.

24. The method of claim 21 in which all of each of the subdocuments is displayed at one time on the client device.

25. The method of claim 21 in which less than all of each of the subdocuments is displayed on the client device at one time.

26, A method comprising displaying a subdocument of a document on a client device, displaying an icon with the subdocument, and in response to invocation of the icon, fetching another subdocument of the document from a server and displaying the other subdocument on the client device, each of the subdocuments being less than the entire document, the subdocuments being of approximately the same size.

27. The method of claim 26 in which only a portion of each of the subdocuments is displayed at one time.

28. The method of claim 27 also including displaying an indication of the position of the currently displayed subdocument in a series of subdocuments that make up the document.

29. The method of claim 28 in which the indication induces the total number of subdocuments in the series and the position of the currently displayed document in the sequence.

30. The method of 1, 17, or 21 in which the subdocuments are derived from the document at the time of a request from the client device for the document.

31. The method of claim 30 in which the subdocuments are derived in a manner that is based on characteristics of the client device.

32. The method of claim 31 in which the characteristics of the client device are provided by the client in connection with the request.

33. The method of claim 32 in which the characteristics include the display capabilities of the client device.

34. The method of claim 1, 17, or 21 in which the subdocuments are derived from the document before the client requests the document from the server.

35. The method of claim 34 in which subdocuments are derived for different documents from different origin servers.

36. The method of claim 1, 17, or 21 in which the subdocuments are derived from the document at a wireless communication gateway.

37. Apparatus comprising a network server configured to receive a machine readable file containing a document that is to be served to a client for display on a client device, and to derive subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments.

38. Apparatus comprising means for receiving a machine readable file containing a document that is to be served to a client for display on a client device, and means for deriving subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments.

39. A machine-readable program stored on a machine-readable medium and capable of configuring a machine to receive a machine readable file containing a document that is to be served to a client for display on a client device, and derive subdocuments from the file, each of the subdocuments being expressed in a format that permits it to be served separately to the client using a hypertext transmission protocol, at least one of the subdocuments containing information that enables it to be linked to another one of the subdocuments.

40. The method of claim 7 in which the file comprises an electronic document.

41. The method of claim 7 in which the file comprises an email file.

42. The method of claim 7 in which the file is received from the origin server in the form of a webpage. -