INTERACTIVE DEVICE NETWORK REGISTRATION PROTOCOL

Abstract: In a network connected to an interactive device and a registration server, a protocol for registering the interactive device with the registration server, including the steps of: installing a secret key and a public unique identifier in non-volatile memory in the interactive device and in a database of the registration server, before the interactive device is connected to the network; then, when the interactive device is connected to the network, authenticating the interactive device at the server by verifying the interactive device's encryption, using the secret key, of a challenge message; and finally, if the authentication succeeds, registering the interactive device in the database of the registration server.

Description: INTERACTIVE DEVICE NETWORK REGISTRATION PROTOCOL FIELD OF INVENTION The present invention relates generally to methods, systems and apparatus for interacting with computers In particular the invention relates to a registration protocol for an interactive device on a network The invention has been developed primarily to allow a large number ol distπbuted users to interact with networked information via printed matter and optical sensors, thereby to obtain interactive printed matter on demand via high-speed networked color printers Although the invention will largely be described heτeιn with reference to this use, it will be appreciated that the invention is not limited to use in this field CO-PENDING APPLICATIONS Various methods sy stems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee ol the present invention simultaneously w ith the present application PCT/AU00/00518, PCT/AU00/00519, PCT/AUOO/00520, PCT/AU00/00521. PCT/AU00/00523, PCT/AUOO/00524. PCT/AU00/00525. PCT/AU00/00526, PCT/AU00/00527, PCT/AUOO/00528, PCT/AU00/00529. PCT/AU00/00530, PCT/AU00/00531. PCT/AUOO/00532. PCT/AUOO/00533, PCT/AU00/00534, PCT/AU00/00535. PCT/AU00/00536, PCT/AUOO/00537, PCT/AU00/00538, PCT/AU00/00539. PCT/AU00/00540, PCT/AU00/00541 , PCT/AU00/00542. PCT/AUOO/00543, PCI/AU00/00544. PCT/AUOO/00545. PCT/AU00/00547 PCT/AU00/00546. PCT/AU00/00554, PCT/AU00/00556, PCT/AU00/00557, PCT/AU00/00558, PCT/AU00/00559, PCT/AU00/00560, PCT/AU00/00561, PCT/AU00/00562, PCT/AU00/00563, PCT/AU00/00564, PCT/AUOO/00566, PCT/AU00/00567, PCT/AUOO/00568. PCT/AU00/00569. PCT/AU00/00570. PCT/AU00/00571 , PCT/AUOO/00572, PCT/AU00/00573. PCT/AU00/00574, PCT/AUOO/00575. PCT/AU00/00576, PCT/AUOO/00577. PCT/AU00/00578. PCT/AU00/00579, PCT/AUO0/00581 , PCT/AU00/00580, PCT/AU00/00582. PCT/AUOO/00587. PC1/AU00/00588. PCT/AU00/00589. PC1 /AU00/00583, PCT/AU00/00593. PCT/AU00/00590, PCT/AU00/00591 , PCT/AU00/00592. PCT/AU00/00594. PCT/AU00/00595. PCT/AU00/00596. PCT/AU00/00597, PCT/AU00/00598. PCT/AU00/00516, and PCT/AU00/00517 The disclosures of these co-pending applications are incorporated herein by cross-reference BACKGROUND Cryptography is used to protect sensitive information, both in storage and in transit, and to authenticate parties to a transaction There are two classes of cryptography in widespread use secret-key cryptography and public-key cryptography Secret-key cryptography, also referred to as symmetric cryptography, uses the same key to encrypt and decrypt a message Two parties wishing to exchange messages must first arrange to securely exchange the secret key An interactive device which is dynamically connected to a network may need to be authenticated and registered before it can be used OBJECT It is an object of the present invention to apply advantages of cryptography to device registration in a network - 1a - SUMMARY OF INVENTION The invention is a protocol for registering an interactive device with a registration server in a network connected to the interactive device and the registration server It includes the steps of installing a secret key and a public unique identifier in non-volatile memory in the interactive device and in a database of the registration server, before the interactive device is connected to the network, then when the interactive device is connected to the network, authenticating the interactive device at the server by verifying the interactive device s encryption, using the secret key, of a challenge message issued by the serv er, and finally, if the authentication succeeds, registering the interactive device in the database of the registration server The challenge preferably includes a nonce, a random or serially-allocated one- - 2 - time-use number The protocol may mclude generating a session key at the server and transmitting the session key to the mteractive device, protected by the shared secret key, for use m protecting commumcations between the mteractive device and server The mteractive device is preferably connected w relessly to the network via a base station which may mclude a pπnter The base station preferably issues the challenge message in place of the server, and the base station preferably stores the session key for use m protecting commumcations between the mteractive device and base station The prmter preferably pnnts documents on demand m response to mputs from the mteractive device The mteractive device preferably generates such mputs by sensmg coded data prmted on documents The pπnter is preferably capable of pπnting such coded data on documents, at the same time as it pnnts normal graphic document content such as text and pictures In a preferred embodiment, the mteractive device takes the form of a pen which is capable of markmg a document at the same time as sensmg the coded data Preferably, the pen is also capable of sensmg its on movement relative to a document BRIEF DESCRIPTION OF DRAWINGS Preferred and other embodiments of the mvention will now be descnbed, by way of non-limiting example only, with reference to the accompanying drawings, m which Figure 1 is a schematic of a the relationship between a sample pnnted netpage and its online page descnption, Figure 2 is a schematic view of a mteraction between a netpage pen, a netpage pnnter, a netpage page server, and a netpage application server, Figure 3 illustrates a collection of netpage servers and prmters interconnected via a network, Figure 4 is a schematic view of a high-level structure of a prmted netpage and its online page descnption, Figure 5 is a plan view showing a structure of a netpage tag, Figure 6 is a plan view showing a relationship between a set of the tags shown in Figure 5 and a field of view of a netpage sensmg device in the form of a netpage pen, Figure 7 is a flowchart of a tag image processmg and decodmg algoπthm, Figure 8 is a perspective view of a netpage pen and its associated tag-sensing fϊeld-of-view cone, Figure 9 is a perspective exploded view of the netpage pen shown m Figure 8, Figure 10 is a schematic block diagram of a pen controller for the netpage pen shown m Figures 8 and 9, Figure 11 is a perspective view of a wall-mounted netpage prmter, Figure 12 is a section through the length of the netpage pnnter of Figure 11, Figure 12a is an enlarged portion of Figure 12 showing a section of the duplexed pnnt engmes and glue wheel assembly, Figure 13 is a detailed view of the ink cartndge, ink, air and glue paths, and pπnt engmes of the netpage pnnter of Figures 11 and 12, Figure 14 is a schematic block diagram of a pnnter controller for the netpage pnnter shown in Figures 11 and 12, Figure 15 is a schematic block diagram of duplexed pnnt engme controllers and Memjet™ printheads associated with the pπnter controller shown m Figure 14, Figure 16 is a schematic block diagram of the pπnt engme controller shown m Figures 14 and 15, Figure 17 is a perspective view of a smgle Memjet™ prmtmg element, as used in, for example, the netpage pnnter of Figures 10 to 12, Figure 18 is a perspective view of a small part of an array of Memjet™ printing elements, Figure 19 is a senes of perspective views illustrating the operating cycle of the Memjet™ printing element shown m Figure 13, Figure 20 is a perspective view of a short segment of a pagewidth Memjet™ prmthead, Figure 21 is a schematic view of a user class diagram, Figure 22 is a schematic view of a pnnter class diagram, Figure 23 is a schematic view of a pen class diagram, Figure 24 is a schematic view of an application class diagram, Figure 25 is a schematic view of a document and page descnption class diagram, Figure 26 is a schematic view of a document and page ownership class diagram, Figure 27 is a schematic view of a terminal element specialization class diagram, Figure 28 is a schematic view of a static element specialization class diagram, Figure 29 is a schematic view of a hyperlink element class diagram, Figure 30 is a schematic view of a hyperlink element specialization class diagram, Figure 31 is a schematic view of a hyperlinked group class diagram, Figure 32 is a schematic view of a form class diagram, Figure 33 is a schematic view of a digital ink class diagram, Figure 34 is a schematic view of a field element specialization class diagram, Figure 35 is a schematic view of a checkbox field class diagram, Figure 36 is a schematic view of a text field class diagram, Figure 37 is a schematic view of a signature field class diagram, Figure 38 is a flowchart of an mput processmg algonthm, Figure 38a is a detailed flowchart of one step of the flowchart of Figure 38, Figure 39 is a schematic view of a page server command element class diagram, Figure 40 is a schematic view of a resource descnption class diagram, Figure 41 is a schematic view of a favontes list class diagram, Figure 42 is a schematic view of a history list class diagram, Figure 43 is a schematic view of a subscnption delivery protocol, Figure 44 is a schematic view of a hyperlink request class d agram, Figure 45 is a schematic view of a hyperlink activation protocol, Figure 46 is a schematic view of a handwnting recognition protocol, Figure 47 is a schematic view of a signature venfication protocol, Figure 48 is a schematic view of a form submission protocol, Figure 49 is a schematic view of a commission payment protocol, Figure 50 is a schematic view of a pnnter registration protocol, Figure 51 is a schematic view of a Web terminal authorization protocol, Figure 52 is a schematic view of a Web terminal prmtmg protocol, Figure 53 is a schematic view of a pen connection protocol, Figure 54 is a schematic view of a pen registration protocol, and Figure 55 is a schematic view of a pen data exchange protocol DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS Note Memjet™ is a trade mark of Silverbrook Research Pty Ltd, Australia In the preferred embodiment, the mvention is configured to work with the netpage networked computer - 4 - system, a detailed overview of which follows It will be appreciated that not every implementation will necessaπly embody all or even most of the specific details and extensions discussed below m relation to the basic system However, the system is descπbed m its most complete form to reduce the need for external reference when attemptmg to understand the context in which the prefened embodiments and aspects of the present mvention operate In bnef summary, the prefened form of the netpage system employs a computer mterface m the form of a mapped surface, that is, a physical surface which contams references to a map of the surface mamtamed m a computer system The map references can be quened by an appropnate sensmg device Dependmg upon the specific implementation, the map references may be encoded visibly or invisibly, and defined in such a way that a local query on the mapped surface yields an unambiguous map reference both withm the map and among different maps The computer system can contain information about features on the mapped surface, and such information can be retneved based on map references supplied by a sensing device used with the mapped surface The information thus retneved can take the form of actions which are initiated by the computer system on behalf of the operator m response to the operator's mteraction with the surface features In its preferred form, the netpage system relies on the production of, and human mteraction with, netpages These are pages of text, graphics and images pnnted on ordinary paper, but which work like mteractive web pages Information is encoded on each page usmg ink which is substantially invisible to the unaided human eye The ink, however, and thereby the coded data, can be sensed by an optically imaging pen and transmitted to the netpage system In the preferred form, active buttons and hyperlinks on each page can be clicked with the pen to request information from the network or to signal preferences to a network server In one embodiment, text wntten by hand on a netpage is automatically recognized and converted to computer text m the netpage system, allowmg forms to be filled m In other embodiments, signatures recorded on a netpage are automatically venfied, allowmg e-commerce transactions to be securely authorized As illustrated m Figure 1 , a pnnted netpage 1 can represent a mteractive form which can be filled m by the user both physically, on the pnnted page, and "electronically", via commumcation between the pen and the netpage system The example shows a "Request" form contammg name and address fields and a submit button The netpage consists of graphic data 2 pnnted usmg visible ink, and coded data 3 pnnted as a collection of tags 4 usmg invisible ink The conespondmg page descnption 5, stored on the netpage network, descπbes the individual elements of the netpage In particular it descnbes the type and spatial extent (zone) of each mteractive element (l e text field or button m the example), to allow the netpage system to correctly mterpret mput via the netpage The submit button 6, for example, has a zone 7 which corresponds to the spatial extent of the corresponding graphic 8 As illustrated m Figure 2, the netpage pen 101, a preferred form of which is shown m Figures 8 and 9 and descnbed m more detail below, works m conjunction with a netpage pπnter 601, an Internet-connected printing appliance for home, office or mobile use The pen is wireless and communicates securely with the netpage pπnter via a short-range radio link 9 The netpage pnnter 601, a preferred form of which is shown m Figures 11 to 13 and descπbed m more detail below, is able to deliver, peπodically or on demand, personalized newspapers, magazines, catalogs, brochures and other publications, all pnnted at high quality as mteractive netpages Unlike a personal computer, the netpage pnnter is an appliance which can be, for example, wall-mounted adjacent to an area where the morning news is first consumed, such as m a user's kitchen, near a breakfast table, or near the household's pomt of departure for the day It also comes m tabletop, desktop, portable and miniature versions Netpages pnnted at then pomt of consumption combme the ease-of-use of paper with the timeliness and interactivity of an mteractive medium As shown in Figure 2, the netpage pen 101 interacts with the coded data on a pnnted netpage 1 and commumcates, via a short-range radio link 9, the mteraction to a netpage pnnter The pnnter 601 sends the mteraction to the relevant netpage page server 10 for mteφretation In appropnate circumstances, the page server sends a conespondmg message to application computer software running on a netpage application server 13 The application server may m turn send a response which is pnnted on the ongmating pnnter The netpage system is made considerably more convement m the preferred embodiment by bemg used m conjunction with high-speed microelectromechanical system (MEMS) based Inkjet (Memjet™) prmters In the prefened form of this technology, relatively high-speed and high-quality pπnting is made more affordable to consumers In its prefened form, a netpage publication has the physical charactenstics of a traditional newsmagazme, such as a set of letter-size glossy pages pnnted m full color on both sides, bound together for easy navigation and comfortable handling The netpage pπnter exploits the growing availability of broadband Internet access Cable service is available to 95% of households m the United States, and cable modem service offering broadband Internet access is aheady available to 20% of these The netpage pπnter can also operate with slower connections, but with longer delivery times and lower image quality Indeed, the netpage system can be enabled usmg existing consumer Inkjet and laser prmters, although the system will operate more slowly and will therefore be less acceptable from a consumer's point of view In other embodiments, the netpage system is hosted on a pnvate intranet In still other embodiments, the netpage system is hosted on a smgle computer or computer-enabled device, such as a pπnter Netpage publication servers 14 on the netpage network are configured to deliver print-quality publications to netpage printers Penodical publications are delivered automatically to subscnbing netpage printers via pointcasting and multicasting Internet protocols Personalized publications are filtered and formatted accordmg to individual user profiles A netpage pnnter can be configured to support any number of pens, and a pen can work with any number of netpage prmters In the prefened implementation, each netpage pen has a umque identifier A household may have a collection of colored netpage pens, one assigned to each member of the family This allows each user to maintain a distinct profile with respect to a netpage publication server or application server A netpage pen can also be registered with a netpage registration server 11 and linked to one or more payment card accounts This allows e-commerce payments to be securely authorized using the netpage pen The netpage registration server compares the signature captured by the netpage pen with a previously registered signature, allowing it to authenticate the user's identity to an e-commerce server Other biometπcs can also be used to venfy identity A version of the netpage pen mcludes fingerprint scanning, venfied m a similar way by the netpage registration server Although a netpage pnnter may deliver penodicals such as the morning newspaper without user intervention, it can be configured never to deliver unsolicited junk mail In its prefened form, it only delivers penodicals from subscnbed or otherwise authorized sources In this respect, the netpage pnnter is unlike a fax machine or e-mail account which is visible to any junk mailer who knows the telephone number or email address 1 NETPAGE SYSTEM ARCHITECTURE Each object model m the system is descnbed usmg a Unified Modelmg Language (UML) class diagram A class diagram consists of a set of object classes connected by relationships, and two lands of relationships are of interest here associations and generalizations An association represents some land of relationship between objects, l e between instances of classes A generalization relates actual classes, and can be understood m the following way if a class is thought of as the set of all objects of that class, and class A is a generalization of class B, then B is simply a subset of A The UML does not directly support second-order modelling - 1 e classes of classes Each class is drawn as a rectangle labelled with the name of the class It contams a list of the attnbutes of the class, separated from the name by a horizontal lme, and a list of the operations of the class, separated from the attnbute list by a horizontal lme In the class diagrams which follow, however, operations are never modelled An association is drawn as a lme joining two classes, optionally labelled at either end with the multiplicity of the association The default multiplicity is one An astensk (*) mdicates a multiplicity of "many", 1 e zero or more Each association is optionally labelled with its name, and is also optionally labelled at either end with the role of the conespondmg class An open diamond mdicates an aggregation association ("is-part-of '), and is drawn at the aggregator end of the association lme A generalization relationship ("ιs-a") is drawn as a solid lme jommg two classes, with an arrow (m the form of an open tnangle) at the generalization end When a class diagram is broken up mto multiple diagrams, any class which is duplicated is shown with a dashed outline m all but the mam diagram which defines it It is shown with attnbutes only where it is defined 1.1 NETPAGES Netpages are the foundation on which a netpage network is built They provide a paper-based user mterface to published information and mteractive services A netpage consists of a pnnted page (or other surface region) invisibly tagged with references to an online descnption of the page The online page descnption is mamtamed persistently by a netpage page server The page descnption descπbes the visible layout and content of the page, mcludmg text, graphics and images It also descnbes the mput elements on the page, mcludmg buttons, hyperlinks, and mput fields A netpage allows markings made with a netpage pen on its surface to be simultaneously captured and processed by the netpage system Multiple netpages can share the same page descnption However, to allow mput through otherwise identical pages to be distinguished, each netpage is assigned a umque page identifier This page ID has sufficient precision to distinguish between a very large number of netpages Each reference to the page descnption is encoded m a pnnted tag The tag identifies the umque page on which it appears, and thereby indnectly identifies the page descnption The tag also identifies its own position on the page Charactenstics of the tags are descnbed m more detail below Tags are pnnted m infrared-absorptive mk on any substrate which is infrared-reflective, such as ordinary paper Near-infrared wavelengths are invisible to the human eye but are easily sensed by a solid-state image sensor with an appropnate filter A tag is sensed by an area image sensor m the netpage pen, and the tag data is transmitted to the netpage system via the nearest netpage pnnter The pen is wireless and commumcates with the netpage pπnter via a short-range radio link Tags are sufficiently small and densely arranged that the pen can reliably image at least one tag even on a smgle click on the page It is important that the pen recognize the page ID and position on every mteraction with the page, smce the mteraction is stateless Tags are enor-correctably encoded to make them partially tolerant to surface damage The netpage page server maintains a umque page mstance for each pnnted netpage, allowmg it to maintain a distinct set of user-supplied values for mput fields m the page descnption for each pnnted netpage The relationship between the page descnption, the page mstance, and the pnnted netpage is shown m Figure 4 The page mstance is associated with both the netpage pπnter which pnnted it and, if known, the netpage user who requested it 1.2 NETPAGE TAGS 1.2.1 Tag Data Content In a preferred form, each tag identifies the region m which it appears, and the location of that tag within the region A tag may also contam flags which relate to the region as a whole or to the tag One or more flag bits may, for example, signal a tag sensmg device to provide feedback mdicative of a function associated with the immediate area of the tag, without the sensmg device havmg to refer to a descnption of the region A netpage pen may, for example, illuminate an "active area" LED when m the zone of a hyperlink As will be more clearly explained below, m a prefened embodiment, each tag contams an easily recognized mvaπant structure which aids initial detection, and which assists m minimizing the effect of any warp mduced by the surface or by the sensmg process The tags preferably tile the entire page, and are sufficiently small and densely ananged that the pen can reliably image at least one tag even on a smgle click on the page It is important that the pen recognize the page ID and position on every mteraction with the page, smce the interaction is stateless In a prefened embodiment, the region to which a tag refers comcides with an entire page, and the region ID encoded m the tag is therefore synonymous with the page ID of the page on which the tag appears In other embodiments, the region to which a tag refers can be an arbitrary subregion of a page or other surface For example, it can comcide with the zone of an mteractive element, m which case the region ID can directly identify the mteractive element Table 1 - Tag data Each tag contams 120 bits of information, typically allocated as shown m Table 1 Assuming a maximum tag density of 64 per square mch, a 16-bit tag ID supports a region size of up to 1024 square mches Larger regions can be mapped continuously without mcreasmg the tag ID precision simply by usmg abutting regions and maps The 100-bit region ID allows 2 100 (~10 ,c or a million trillion tπllion) different regions to be uniquely identified 1.2.2 Tag Data Encoding The 120 bits of tag data are redundantly encoded usmg a (15, 5) Reed-Solomon code This yields 360 encoded bits consisting of 6 codewords of 15 4-bit symbols each The (15, 5) code allows up to 5 symbol enors to be conected per codeword, l e it is tolerant of a symbol enor rate of up to 33% per codeword Each 4-bit symbol is represented in a spatially coherent way m the tag, and the symbols of the six codewords are mterleaved spatially withm the tag This ensures that a burst enor (an enor affecting multiple spatially adjacent bits) damages a minimum number of symbols overall and a minimum number of symbols m any one codeword, thus maximising the likelihood that the burst enor can be fully conected 1.2.3 Physical Tag Structure The physical representation of the tag, shown m Figure 5, mcludes fixed target structures 15, 16, 17 and vanable data areas 18 The fixed target structures allow a sensmg device such as the netpage pen to detect the tag and infer its three-dimensional onentation relative to the sensor The data areas contam representations of the individual bits of the encoded tag data To achieve proper tag reproduction, the tag is rendered at a resolution of 256x256 dots When pnnted at 1600 dots per mch this yields a tag with a diameter of about 4 mm At this resolution the tag is designed to be sunounded by a "quiet area" of radius 16 dots Smce the quiet area is also contnbuted by adjacent tags, it only adds 16 dots to the effective diameter of the tag - 8 - The tag mcludes six target structures A detection ring 15 allows the sensmg device to initially detect the tag The ring is easy to detect because it is rotationally mvanant and because a simple conection of its aspect ratio removes most of the effects of perspective distortion An onentation axis 16 allows the sensmg device to determine the approximate planar onentation of the tag due to the yaw of the sensor The onentation axis is skewed to yield a umque onentation Four perspective targets 17 allow the sensmg device to mfer an accurate two-dimensional perspective transform of the tag and hence an accurate three-dimensional position and onentation of the tag relative to the sensor All target structures are redundantly large to improve their immunity to noise The overall tag shape is circular This supports, amongst other things, optimal tag packing on an irregular tnangular gnd In combination with the cncular detection ring, this makes a circular arrangement of data bits withm the tag optimal To maximise its size, each data bit is represented by a radial wedge m the form of an area bounded by two radial lmes and two concentnc circular arcs Each wedge has a minimum dimension of 8 dots at 1600 dpi and is designed so that its base (its inner arc), is at least equal to this minimum dimension The height of the wedge m the radial dnection is always equal to the minimum dimension Each 4-bit data symbol is represented by an anay of 2x2 wedges The 15 4-bit data symbols of each of the six codewords are allocated to the four concentnc symbol rings 18a to 18d in mterleaved fashion Symbols are allocated alternately m circular progression around the tag The mterleavmg is designed to maximise the average spatial distance between any two symbols of the same codeword In order to support "single-click" mteraction with a tagged region via a sensmg device, the sensmg device must be able to see at least one entire tag m its field of view no matter where m the region or at what onentation it is positioned The required diameter of the field of view of the sensmg device is therefore a function of the size and spacmg of the tags Assuming a circular tag shape, the minimum diameter of the sensor field of view is obtained when the tags are tiled on a equilateral tnangular gnd, as shown in Figure 6 1.2.4 Tag Image Processing and Decoding The tag image processmg and decoding performed by a sensmg device such as the netpage pen is shown m Figure 7 While a captured image is bemg acquired from the image sensor, the dynamic range of the image is determined (at 20) The center of the range is then chosen as the binary threshold for the image 21 The image is then thresholded and segmented mto connected pixel regions (l e shapes 23) (at 22) Shapes which are too small to represent tag target structures are discarded The size and centroid of each shape is also computed Binary shape moments 25 are then computed (at 24) for each shape, and these provide the basis for subsequently locating target structures Central shape moments are by then nature mvanant of position, and can be easily made mvanant of scale, aspect ratio and rotation The ring target structure 15 is the first to be located (at 26) A πng has the advantage of bemg very well behaved when perspective-distorted Matchmg proceeds by aspect-normalizmg and rotation-normalizmg each shape's moments Once its second-order moments are normalized the ring is easy to recognize even if the perspective distortion was significant The ring's ongmal aspect and rotation 27 together provide a useful approximation of the perspective transform The axis target structure 16 is the next to be located (at 28) Match g proceeds by applymg the ring's normalizations to each shape's moments, and rotation-normalizmg the resulting moments Once its second-order moments are normalized the axis target is easily recognized Note that one third order moment is required to disambiguate the two possible onentations of the axis The shape is deliberately skewed to one side to make this possible Note also that it is only possible to rotation-normalize the axis target after it has had the nng's normalizations applied, smce the perspective distortion can hide the axis target's axis The axis target's ongmal rotation provides a useful approximation of the tag's rotation due to pen yaw 29 The four perspective target structures 17 are the last to be located (at 30) Good estimates of then positions are computed based on their known spatial relationships to the πng and axis targets, the aspect and rotation of the ring, and the rotation of the axis Matchmg proceeds by applymg the nng's normalizations to each shape's moments Once then second-order moments are normalized the circular perspective targets are easy to recognize, and the target closest to each estimated position is taken as a match The ongmal centroids of the four perspective targets are then taken to be the perspective-distorted comers 31 of a square of known size m tag space, and an eight-degree-of-freedom perspective transform 33 is mfened (at 32) based on solvmg the well-understood equations relating the four tag-space and image- space point pans (see Heckbert, P , Fundamentals of Texture Mappmg and Image Warpmg, Masters Thesis, Dept of EECS, U of California at Berkeley, Technical Report No UCB/CSD 89/516, June 1989, the contents of which are herem mcoφorated by cross-reference) The mfened tag-space to image-space perspective transform is used to project (at 36) each known data bit position in tag space mto image space where the real-valued position is used to bilinearly inteφolate (at 36) the four relevant adjacent pixels m the mput image The previously computed image threshold 21 is used to threshold the result to produce the final bit value 37 Once all 360 data bits 37 have been obtained m this way, each of the six 60-bit Reed-Solomon codewords is decoded (at 38) to yield 20 decoded bits 39, or 120 decoded bits m total Note that the codeword symbols are sampled m codeword order, so that codewords are implicitly de-mterleaved duπng the sampling process The ring target 15 is only sought m a subarea of the image whose relationship to the image guarantees that the πng, if found, is part of a complete tag If a complete tag is not found and successfully decoded, then no pen position is recorded for the cunent frame Given adequate processmg power and ideally a non-minimal field of view 193, an alternative strategy mvolves seeking another tag m the cunent image The obtained tag data mdicates the identity of the region contammg the tag and the position of the tag withm the region An accurate position 35 of the pen mb m the region, as well as the overall onentation 35 of the pen, is then mfened (at 34) from the perspective transform 33 observed on the tag and the known spatial relationship between the pen's physical axis and the pen's optical axis 1.2.5 Tag Map Decoding a tag results m a region ID, a tag ID, and a tag-relative pen transform Before the tag ID and the tag-relative pen location can be translated mto an absolute location withm the tagged region, the location of the tag withm the region must be known This is given by a tag map, a function which maps each tag ID m a tagged region to a conespondmg location The tag map class diagram is shown m Figure 22, as part of the netpage pnnter class diagram A tag map reflects the scheme used to tile the surface region with tags, and this can vary accordmg to surface type When multiple tagged regions share the same tilmg scheme and the same tag numbermg scheme, they can also share the same tag map The tag map for a region must be retπevable via the region ID Thus, given a region ID, a tag ID and a pen transform, the tag map can be retneved, the tag ID can be translated mto an absolute tag location withm the region, and the tag-relative pen location can be added to the tag location to yield an absolute pen location withm the region 1.2.6 Tagging Schemes Two distinct surface coding schemes are of mterest, both of which use the tag structure descnbed earlier m this section The prefened coding scheme uses "location-indicating" tags as already discussed An alternative coding - 10 - scheme uses object-mdicating tags A location- dicating tag contams a tag ID which, when translated through the tag map associated with the tagged region, yields a umque tag location withm the region The tag-relative location of the pen is added to this tag location to yield the location of the pen withm the region This m turn is used to determme the location of the pen relative to a user mterface element m the page descnption associated with the region Not only is the user mterface element itself identified, but a location relative to the user mterface element is identified Location-mdicating tags therefore tnvially support the capture of an absolute pen path m the zone of a particular user mterface element An object-mdicating tag contams a tag ID which dnectly identifies a user mterface element m the page descnption associated with the region All the tags m the zone of the user mterface element identify the user mterface element, making them all identical and therefore indistinguishable Object-mdicating tags do not, therefore, support the capture of an absolute pen path They do, however, support the capture of a relative pen path So long as the position sampling frequency exceeds twice the encountered tag frequency, the displacement from one sampled pen position to the next withm a stroke can be unambiguously determined With either tagging scheme, the tags function m cooperation with associated visual elements on the netpage as user mteractive elements m that a user can mteract with the pnnted page usmg an appropnate sensmg device m order for tag data to be read by the sensmg device and for an appropnate response to be generated m the netpage system 1.3 DOCUMENT AND PAGE DESCRIPTIONS A prefened embodiment of a document and page descnption class diagram is shown m Figures 25 and 26 In the netpage system a document is descπbed at three levels At the most abstract level the document 836 has a hierarchical structure whose terminal elements 839 are associated with content objects 840 such as text objects, text style objects, image objects, etc Once the document is pnnted on a pnnter with a particular page size and accordmg to a particular user's scale factor preference, the document is pagmated and otherwise formatted Formatted terminal elements 835 will m some cases be associated with content objects which are different from those associated with then conespondmg terminal elements, particularly where the content objects are style-related Each pnnted mstance of a document and page is also descnbed separately, to allow mput captured through a particular page mstance 830 to be recorded separately from mput captured through other instances of the same page descnption The presence of the most abstract document descnption on the page server allows a user to request a copy of a document without bemg forced to accept the source document's specific format The user may be requesting a copy through a pπnter with a different page size, for example Conversely, the presence of the formatted document descnption on the page server allows the page server to efficiently inteφret user actions on a particular pnnted page A formatted document 834 consists of a set of formatted page descnptions 5, each of which consists of a set of formatted terminal elements 835 Each formatted element has a spatial extent or zone 58 on the page This defines the active area of mput elements such as hyperlinks and mput fields A document mstance 831 conesponds to a formatted document 834 It consists of a set of page instances 830, each of which conesponds to a page descnption 5 of the formatted document Each page mstance 830 descπbes a smgle umque pnnted netpage 1, and records the page ID 50 of the netpage A page mstance is not part of a document mstance if it represents a copy of a page requested m isolation A page mstance consists of a set of terminal element instances 832 An element mstance only exists if it records instance-specific information Thus, a hyperlink mstance exists for a hyperlink element because it records a transaction ID 55 which is specific to the page mstance, and a field mstance exists for a field element because it records input specific to the page mstance An element mstance does not exist, however, for static elements such as textflows A terminal element can be a static element 843, a hyperlink element 844, a field element 845 or a page - 11 - server command element 846, as shown m Figure 27 A static element 843 can be a sfyle element 847 with an associated sfyle object 854, a textflow element 848 with an associated sfyled text object 855, an image element 849 with an associated image element 856, a graphic element 850 with an associated graphic object 857, a video clip element 851 with an associated video clip object 858, an audio clip element 852 with an associated audio clip object 859, or a scnpt element 853 with an associated scnpt object 860, as shown m Figure 28 A page mstance has a background field 833 which is used to record any digital ink captured on the page which does not apply to a specific mput element In the prefened form of the mvention, a tag map 811 is associated with each page mstance to allow tags on the page to be translated mto locations on the page 1.4 THE NETPAGE NETWORK In a prefened embodiment, a netpage network consists of a distnbuted set of netpage page servers 10, netpage registration servers 11, netpage ID servers 12, netpage application servers 13, netpage publication servers 14, and netpage prmters 601 connected via a network 19 such as the Internet, as shown m Figure 3 The netpage registration server 11 is a server which records relationships between users, pens, prmters, applications and publications, and thereby authorizes vanous network activities It authenticates users and acts as a signing proxy on behalf of authenticated users m application transactions It also provides handwnting recognition services As descπbed above, a netpage page server 10 maintains persistent information about page descnptions and page instances The netpage network mcludes any number of page servers, each handling a subset of page instances Smce a page server also maintains user mput values for each page mstance, clients such as netpage prmters send netpage mput chrectly to the appropnate page server The page server inteφrets any such mput relative to the descnption of the conespondmg page A netpage ID server 12 allocates document IDs 51 on demand, and provides load-balancing of page servers via its ID allocation scheme A netpage pnnter uses the Internet Distnbuted Name System (DNS), or similar, to resolve a netpage page ID 50 mto the network address of the netpage page server handling the conespondmg page mstance A netpage application server 13 is a server which hosts mteractive netpage applications A netpage publication server 14 is an application server which publishes netpage documents to netpage prmters They are descnbed in detail m Section 2 Netpage servers can be hosted on a vanety of network server platforms from manufacturers such as IBM, Hewlett-Packard, and Sun Multiple netpage servers can run concunently on a smgle host, and a smgle server can be distnbuted over a number of hosts Some or all of the functionality provided by netpage servers, and m particular the functionality provided by the ID server and the page server, can also be provided dnectly m a netpage appliance such as a netpage pπnter, m a computer workstation, or on a local network 1.5 THE NETPAGE PRINTER The netpage pπnter 601 is an appliance which is registered with the netpage system and pnnts netpage documents on demand and via subscnption Each pπnter has a umque pπnter ID 62, and is connected to the netpage network via a network such as the Internet, ideally via a broadband connection Apart from identify and secunty settings m non-volatile memory, the netpage pnnter contams no persistent storage As far as a user is concerned, "the network is the computer" Netpages function interactively across space and time with the help of the distπbuted netpage page servers 10, independently of particular netpage prmters The netpage pπnter receives subscnbed netpage documents from netpage publication servers 14 Each document is distnbuted m two parts the page layouts, and the actual text and image objects which populate the pages - 12 - Because of personalization, page layouts are typically specific to a particular subscnber and so are pomtcast to the subscπber's pnnter via the appropnate page server Text and image objects, on the other hand, are typically shared with other subscnbers, and so are multicast to all subscnbers' prmters and the appropnate page servers The netpage publication server optimizes the segmentation of document content mto pointcasts and multicasts After receivmg the pomtcast of a document's page layouts, the pnnter knows which multicasts, if any, to listen to Once the pnnter has received the complete page layouts and objects that define the document to be pnnted, it can pπnt the document The printer rastenzes and pnnts odd and even pages simultaneously on both sides of the sheet It contams duplexed pπnt engine controllers 760 and pnnt engmes utilizing Memjet™ printheads 350 for this piupose The prmtmg process consists of two decoupled stages rasterization of page descnptions, and expansion and prmtmg of page images The raster image processor (RIP) consists of one or more standard DSPs 757 running m parallel The duplexed pnnt engme controllers consist of custom processors which expand, dither and pnnt page images m real tune, synchronized with the operation of the pπntheads m the pπnt engmes Pnnters not enabled for IR prmtmg have the option to pnnt tags usmg IR-absoφtive black ink, although this restncts tags to otherwise empty areas of the page Although such pages have more limited functionality than IR-pπnted pages, they are still classed as netpages A normal netpage pnnter pnnts netpages on sheets of paper More specialised netpage pnnters may pπnt onto more specialised surfaces, such as globes Each pnnter supports at least one surface type, and supports at least one tag tilmg scheme, and hence tag map, for each surface type The tag map 811 which descπbes the tag tiling scheme actually used to pnnt a document becomes associated with that document so that the document's tags can be conectly inteφreted Figure 2 shows the netpage pnnter class diagram, reflecting pπnter-related information mamtamed by a registration server 11 on the netpage network A prefened embodiment of the netpage pnnter is descnbed m greater detail m Section 6 below, with reference to Figures 11 to 16 1.5.1 Memjet™ Printheads The netpage system can operate usmg pnnters made with a wide range of digital pπnting technologies, mcludmg thermal Inkjet, piezoelectnc inkjet, laser electrophotographic, and others However, for wide consumer acceptance, it is desnable that a netpage pnnter have the following charactenstics • photographic qualify color prmtmg high qualify text printing • high reliability • low pnnter cost • low mk cost • low paper cost • simple operation • nearly silent printing • high prmtmg speed • simultaneous double sided pπnting • compact form factor • low power consumption - 13 - No commercially available pπnting technology has all of these charactenstics To enable to production of pnnters with these charactenstics, the present applicant has mvented a new pnnt technology, refened to as Memjet™ technology Memjet™ is a drop-on-demand uikjet technology that mcoφorates pagewidth pπntheads fabncated using microelectromechanical systems (MEMS) technology Figure 17 shows a smgle prmtmg element 300 of a Memjet™ prmthead The netpage wallpnnter rncoφorates 168960 printing elements 300 to form a 1600 dpi pagewidth duplex pnnter This pπnter simultaneously pnnts cyan, magenta, yellow, black, and infrared inks as well as paper conditioner and mk fixative The pπnting element 300 is approximately 110 microns long by 32 microns wide Arrays of these pπnting elements are formed on a silicon substrate 301 that incoφorates CMOS logic, data transfer, timing, and dnve circuits (not shown) Major elements of the printing element 300 are the nozzle 302, the nozzle nm 303, the nozzle chamber 304, the flmdic seal 305, the ink channel nm 306, the lever arm 307, the active actuator beam pair 308, the passive actuator beam pan 309, the active actuator anchor 310, the passive actuator anchor 311, and the ink inlet 312 The active actuator beam pair 308 is mechanically jomed to the passive actuator beam pan 309 at the jom 319 Both beams pans are anchored at then respective anchor points 310 and 311 The combination of elements 308, 309, 310, 311, and 319 form a cantilevered electrothermal bend actuator 320 Figure 18 shows a small part of an aπay of prmtmg elements 300, mcludmg a cross section 315 of a pπnting element 300 The cross section 315 is shown without ink, to clearly show the ink inlet 312 that passes through the silicon wafer 301 Figures 19(a), 19(b) and 19(c) show the operating cycle of a Memjet™ prmtmg element 300 Figure 19(a) shows the quiescent position of the ink memscus 316 pnor to prmtmg an ink droplet Ink is retained m the nozzle chamber by surface tension at the ink meniscus 316 and at the flmdic seal 305 formed between the nozzle chamber 304 and the ink channel nm 306 While prmtmg, the pnnthead CMOS cncuitry distnbutes data from the pnnt engme controller to the conect prmtmg element, latches the data, and buffers the data to dnve the electrodes 318 of the active actuator beam pan 308 This causes an electncal cunent to pass through the beam pan 308 for about one microsecond, resulting m Joule heatmg The temperature increase resulting from Joule heating causes the beam pan 308 to expand As the passive actuator beam pan 309 is not heated, it does not expand, resulting m a stress difference between the two beam pans This stress difference is partially resolved by the cantilevered end of the electrothermal bend actuator 320 bending towards the substrate 301 The lever arm 307 transmits this movement to the nozzle chamber 304 The nozzle chamber 304 moves about two microns to the position shown m Figure 19(b) This mcreases the ink pressure, forcmg ink 321 out of the nozzle 302, and causing the ink memscus 316 to bulge The nozzle nm 303 prevents the ink memscus 316 from spreading across the surface of the nozzle chamber 304 As the temperature of the beam pans 308 and 309 equalizes, the actuator 320 returns to its ongmal position This aids m the break-off of the ink droplet 317 from the ink 321 in the nozzle chamber, as shown m Figure 19(c) The nozzle chamber is refilled by the action of the surface tension at the memscus 316 Figure 20 shows a segment of a pnnthead 350 In a netpage pπnter, the length of the pnnthead is the full width of the paper (typically 210 mm) m the direction 351 The segment shown is 04 mm long (about 0 2% of a complete pnnthead) When pπnting, the paper is moved past the fixed pnnthead m the direction 352 The pnnthead has 6 rows of interdigitated prmtmg elements 300, pπnting the six colors or types of ink supplied by the ink inlets 312 To protect the fragile surface of the pnnthead during operation, a nozzle guard wafer 330 is attached to the pnnthead substrate 301 For each nozzle 302 there is a conesponding nozzle guard hole 331 through which the ink - 14 - droplets are fired To prevent the nozzle guard holes 331 from becommg blocked by paper fibers or other debns, filtered an is pumped through the an inlets 332 and out of the nozzle guard holes during pπnting To prevent mk 321 from drying, the nozzle guard is sealed while the pnnter is idle 1.6 The Netpage Pen The active sensmg device of the netpage system is typically a pen 101, which, usmg its embedded controller 134, is able to capture and decode IR position tags from a page via an image sensor The image sensor is a solid-state device provided with an appropnate filter to permit sensmg at only near-infrared wavelengths As descnbed m more detail below, the system is able to sense when the mb is m contact with the surface, and the pen is able to sense tags at a sufficient rate to capture human handwnting (l e at 200 dpi or greater and 100 Hz or faster) Information captured by the pen is encrypted and wirelessly transmitted to the pnnter (or base station), the pπnter or base station lnteφreting the data with respect to the (known) page structure The prefened embodiment of the netpage pen operates both as a normal markmg ink pen and as a non- marking sfylus The markmg aspect, however, is not necessary for usmg the netpage system as a browsmg system, such as when it is used as an Internet mterface Each netpage pen is registered with the netpage system and has a umque pen ID 61 Figure 23 shows the netpage pen class diagram, reflecting pen-related information mamtamed by a registration server 11 on the netpage network When either mb is m contact with a netpage, the pen determmes its position and onentation relative to the page The mb is attached to a force sensor, and the force on the mb is inteφreted relative to a threshold to indicate whether the pen is "up" or "down" This allows a mteractive element on the page to be 'clicked' by pressmg with the pen mb, m order to request, say, information from a network Furthermore, the force is captured as a continuous value to allow, say, the full dynamics of a signature to be venfied The pen determmes the position and onentation of its mb on the netpage by imaging, m the infrared spectrum, an area 193 of the page in the vicinity of the mb It decodes the nearest tag and computes the position of the mb relative to the tag from the observed perspective distortion on the imaged tag and the known geometry of the pen optics Although the position resolution of the tag may be low, because the tag density on the page is mversely proportional to the tag size, the adjusted position resolution is quite high, exceedmg the minimum resolution requned for accurate handwnting recognition Pen actions relative to a netpage are captured as a senes of strokes A stroke consists of a sequence of time- stamped pen positions on the page, initiated by a pen-down event and completed by the subsequent pen-up event A stroke is also tagged with the page ID 50 of the netpage whenever the page ID changes, which, under normal cncumstances, is at the commencement of the stroke Each netpage pen has a current selection 826 associated with it, allowmg the user to perform copy and paste operations etc The selection is timestamped to allow the system to discard it after a defined time penod The cunent selection descnbes a region of a page mstance It consists of the most recent digital ink stroke captured through the pen relative to the background area of the page It is inteφreted in an application-specific manner once it is submitted to an application via a selection hyperlink activation Each pen has a cunent mb 824 This is the mb last notified by the pen to the system In the case of the default netpage pen descnbed above, either the marking black mk mb or the non-marking sfylus mb is cunent Each pen also has a cunent mb style 825 This is the mb sfyle last associated with the pen by an application, e g m response to the user selecting a color from a palette The default mb sfyle is the mb sfyle associated with the cunent mb Strokes captured through a pen are tagged with the cunent mb sfyle When the strokes are subsequently reproduced, they are reproduced in the mb sfyle with which they are tagged - 15 - Whenever the pen is withm range of a pnnter with which it can communicate, the pen slowly flashes its "online" LED When the pen fails to decode a stroke relative to the page, it momentanly activates its "enor" LED When the pen succeeds m decoding a stroke relative to the page, it momentanly activates its "ok" LED A sequence of captured strokes is refened to as digital ink Digital ink forms the basis for the digital exchange of drawings and handwnting, for online recognition of handwnting, and for online venfication of signatures The pen is wireless and transmits digital ink to the netpage pnnter via a short-range radio link The transmitted digital ink is encrypted for pnvacy and secuπfy and packetized for efficient transmission, but is always flushed on a pen-up event to ensure timely handling m the pπnter When the pen is out-of-range of a pπnter it buffers digital ink m mtemal memory, which has a capacity of over ten mmutes of continuous handwnting When the pen is once agam withm range of a pnnter, it transfers any buffered digital ink A pen can be registered with any number of pnnters, but because all state data resides m netpages both on paper and on the network, it is largely immatenal which pnnter a pen is communicating with at any particular time A prefened embodiment of the pen is descnbed m greater detail m Section 6 below, with reference to Figures 8 to 10 1.7 NETPAGE INTERACTION The netpage pnnter 601 receives data relating to a stroke from the pen 101 when the pen is used to interact with a netpage 1 The coded data 3 of the tags 4 is read by the pen when it is used to execute a movement, such as a stroke The data allows the identify of the particular page and associated mteractive element to be determined and an indication of the relative positioning of the pen relative to the page to be obtained The mdicatmg data is transmitted to the pnnter, where it resolves, via the DNS, the page ID 50 of the stroke mto the network address of the netpage page server 10 which maintains the conespond g page mstance 830 It then transmits the stroke to the page server If the page was recently identified m an earlier stroke, then the pnnter may aheady have the address of the relevant page server m its cache Each netpage consists of a compact page layout mamtamed persistently by a netpage page server (see below) The page layout refers to objects such as images, fonts and pieces of text, typically stored elsewhere on the netpage network When the page server receives the stroke from the pen, it retneves the page descnption to which the stroke applies, and determmes which element of the page descnption the stroke mtersects It is then able to inteφret the stroke m the context of the type of the relevant element A "click" is a stroke where the distance and time between the pen down position and the subsequent pen up position are both less than some small maximum An object which is activated by a click typically requires a click to be activated, and accordingly, a longer stroke is ignored The failure of a pen action, such as a "sloppy" click, to register is mdicated by the lack of response from the pen's "ok" LED There are two lands of mput elements m a netpage page descnption hyperlinks and form fields Input through a form field can also tngger the activation of an associated hyperlink 1.7.1 Hyperlinks A hyperlink is a means of sending a message to a remote application, and typically elicits a pnnted response m the netpage system A hyperlink element 844 identifies the application 71 which handles activation of the hyperlink, a link ID 54 which identifies the hyperlink to the application, an "alias requned" flag which asks the system to mclude the user's application alias ID 65 m the hyperlink activation, and a descnption which is used when the hyperlink is recorded as a favonte or appears in the user's history The hyperlink element class diagram is shown m Figure 29 - 16 - When a hyperlink is activated, the page server sends a request to an application somewhere on the network The application is identified by an application ID 64, and the application ID is resolved m the normal way via the DNS There are three types of hyperlinks general hyperlinks 863, form hyperlinks 865, and selection hyperlinks 864, as shown m Figure 30 A general hyperlink can implement a request for a linked document, or may simply signal a preference to a server A form hyperlink submits the conespondmg form to the application A selection hyperlink submits the current selection to the application If the cunent selection contams a smgle-word piece of text, for example, the application may return a single-page document givmg the word's meaning withm the context m which it appears, or a translation mto a different language Each hyperlink type is characterized by what information is submitted to the application The conespondmg hyperlink mstance 862 records a transaction ID 55 which can be specific to the page mstance on which the hyperlink mstance appears The transaction ID can identify user-specific data to the application, for example a "shopping cart" of pendmg purchases mamtamed by a purchasing application on behalf of the user The system mcludes the pen's cunent selection 826 m a selection hyperlink activation The system mcludes the content of the associated form mstance 868 m a form hyperlink activation, although if the hyperlink has its "submit delta" attnbute set, only mput since the last form submission is mcluded The system mcludes an effective return path m all hyperlink activations A hyperlinked group 866 is a group element 838 which has an associated hyperlink, as shown m Figure 31 When mput occurs through any field element m the group, the hyperlink 844 associated with the group is activated A hyperlinked group can be used to associate hyperlink behavior with a field such as a checkbox It can also be used, m conjunction with the "submit delta" attnbute of a form hyperlink, to provide continuous mput to an application It can therefore be used to support a "blackboard" mteraction model, I e where mput is captured and therefore shared as soon as it occurs 1.7.2 Forms A form defines a collection of related mput fields used to capture a related set of mputs through a pnnted netpage A form allows a user to submit one or more parameters to an application software program running on a server A form 867 is a group element 838 m the document hierarchy It ultimately contams a set of terminal field elements 839 A form mstance 868 represents a pnnted mstance of a form It consists of a set of field instances 870 which conespond to the field elements 845 of the form Each field mstance has an associated value 871, whose type depends on the type of the conesponding field element Each field value records mput through a particular pnnted form mstance, l e through one or more pnnted netpages The form class diagram is shown m Figure 32 Each form mstance has a status 872 which mdicates whether the form is active, frozen, submitted, void or expned A form is active when first pnnted A form becomes frozen once it is signed A form becomes submitted once one of its submission hyperlinks has been activated, unless the hyperlink has its "submit delta" attnbute set A form becomes void when the user mvokes a void form, reset form or duplicate form page command A form expnes when the time the form has been active exceeds the form's specified lifetime While the form is active, form mput is allowed Input through a form which is not active is mstead captured in the background field 833 of the relevant page mstance When the form is active or frozen, form submission is allowed Any attempt to submit a form when the form is not active or frozen is rejected, and mstead elicits an form status report Each form mstance is associated (at 59) with any form instances denved from it, thus providing a version history This allows all but the latest version of a form m a particular time penod to be excluded from a search All mput is captured as digital ink Digital ink 873 consists of a set of timestamped stroke groups 874, each of which consists of a set of sfyled strokes 875 Each stroke consists of a set of timestamped pen positions 876, each of - 17 - which also includes pen onentation and mb force The digital ink class diagram is shown in Figure 33 A field element 845 can be a checkbox field 877, a text field 878, a drawing field 879, or a signature field 880 The field element class diagram is shown m Figure 34 Any digital ink captured m a field's zone 58 is assigned to the field A checkbox field has an associated boolean value 881, as shown m Figure 35 Any mark (a tick, a cross, a stroke, a fill zigzag, etc ) captured m a checkbox field's zone causes a true value to be assigned to the field's value A text field has an associated text value 882, as shown m Figure 36 Any digital mk captured m a text field's zone is automatically converted to text via onlme handwnting recogmtion, and the text is assigned to the field's value Onlme handwnting recognition is well-understood (see, for example, Tappert, C , C Y Suen and T Wakahara, "The State of the Art m On-Line Handwnting Recogmtion", IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol 12, No 8, August 1990, the contents of which are herem incoφorated by cross-reference) A signature field has an associated digital signature value 883, as shown m Figure 37 Any digital ink captured in a signature field's zone is automatically venfied with respect to the identity of the owner of the pen, and a digital signature of the content of the form of which the field is part is generated and assigned to the field's value The digital signature is generated usmg the pen user's pnvate signature key specific to the application which owns the form Online signature venfication is well-understood (see, for example, Plamondon, R and G Lorette, "Automatic Signature Venfication and Wnter Identification - The State of the Art", Pattern Recogmtion, Vol 22, No 2, 1989, the contents of which are herem incoφorated by cross-reference) A field element is hidden if its "hidden" attnbute is set A hidden field element does not have an input zone on a page and does not accept mput It can have an associated field value which is mcluded m the form data when the form contammg the field is submitted "Editing" commands, such as strike-throughs mdicatmg deletion, can also be recognized m form fields Because the handwnting recogmtion algoπthm works "onlme" (I e with access to the dynamics of the pen movement), rather than "offline" (1 e with access only to a bitmap of pen markings), it can recognize run-on discretely- wntten characters with relatively high accuracy, without a wnter-dependent training phase A wnter-dependent model of handwntmg is automatically generated over time, however, and can be generated up-front if necessary, Digital ink, as already stated, consists of a sequence of strokes Any stroke which starts m a particular element's zone is appended to that element's digital ink stream, ready for mteφretation Any stroke not appended to an object's digital ink stream is appended to the background field's digital ink stream Digital ink captured m the background field is inteφreted as a selection gesture Circumscnption of one or more objects is generally inteφreted as a selection of the cncumscπbed objects, although the actual mteφretation is application-specific Table 2 summanses these vanous pen interactions with a netpage Table 2 - Summary of pen interactions with a netpage 18 The system maintains a cunent selection for each pen The selection consists simply of the most recent stroke captured m the background field The selection is cleared after an inactivity timeout to ensure predictable behavior The raw digital ink captured in every field is retained on the netpage page server and is optionally transmitted with the form data when the form is submitted to the application This allows the application to mtenogate the raw digital ink should it suspect the ongmal conversion, such as the conversion of handwπtten text This can, for example, mvolve human intervention at the application level for forms which fail certain application-specific consistency checks As an extension to this, the entire background area of a form can be designated as a drawing field The application can then decide, on the basis of the presence of digital ink outside the explicit fields of the form, to route the form to a human operator, on the assumption that the user may have mdicated amendments to the filled-m fields outside of those fields Figure 38 shows a flowchart of the process of handling pen mput relative to a netpage The process consists of receivmg (at 884) a stroke from the pen, identifymg (at 885) the page mstance 830 to which the page ID 50 m the stroke refers, retnevmg (at 886) the page descnption 5, identifymg (at 887) a formatted element 839 whose zone 58 the stroke mtersects, determining (at 888) whether the formatted element conesponds to a field element, and if so appendmg (at 892) the received stroke to the digital ink of the field value 871, inteφreting (at 893) the accumulated digital ink of the field, and determining (at 894) whether the field is part of a hyperlinked group 866 and if so activating (at 895) the associated hyperlink, alternatively determining (at 889) whether the formatted element conesponds to a hyperlink element and if so activating (at 895) the conespondmg hyperlink, altematively, in the absence of an mput field or hyperlink, appendmg (at 890) the received stroke to the digital ink of the background field 833, and copymg (at 891) the received stroke to the cunent selection 826 of the cunent pen, as mamtamed by the registration server Figure 38a shows a detailed flowchart of step 893 m the process shown in Figure 38, where the accumulated digital ink of a field is inteφreted according to the type of the field The process consists of determining (at 896) whether the field is a checkbox and (at 897) whether the digital mk represents a checkmark, and if so assignmg (at 898) a true value to the field value, alternatively determining (at 899) whether the field is a text field and if so converting (at 900) the digital ink to computer text, with the help of the appropnate registration server, and assignmg (at 901) the converted computer text to the field value, altematively determining (at 902) whether the field is a signature field and if so venfymg (at 903) the digital ink as the signature of the pen's owner, with the help of the appropnate registration server, creating (at 904) a digital signature of the contents of the conespondmg form, also with the help of the registration server and usmg the pen owner's pnvate signature key relating to the conespondmg application, and assignmg (at 905) the digital signature to the field value 1.7.3 Page Server Commands A page server command is a command which is handled locally by the page server It operates directly on form, page and document instances A page server command 907 can be a void form command 908, a duplicate form command 909, a reset form command 910, a get form status command 911, a duplicate page command 912, a reset page command 913, a get page status command 914, a duplicate document command 915, a reset document command 916, or a get document status - 19 - command 917, as shown m Figure 39 A void form command voids the conesponding form mstance A duplicate form command voids the conesponding form mstance and then produces an active pnnted copy of the cunent form mstance with field values preserved The copy contams the same hyperlink transaction IDs as the ongmal, and so is mdistingmshable from the ongmal to an application A reset form command voids the conespondmg form mstance and then produces an active pnnted copy of the form mstance with field values discarded A get form status command produces a pnnted report on the status of the conespondmg form mstance, mcludmg who published it, when it was pnnted, for whom it was pnnted, and the form status of the form mstance Since a form hyperlink instance contains a transaction ID, the application has to be involved m producmg a new form mstance A button requestmg a new form instance is therefore typically implemented as a hyperlink A duplicate page command produces a pnnted copy of the conesponding page mstance with the background field value preserved If the page contains a form or is part of a form, then the duplicate page command is inteφreted as a duplicate form command A reset page command produces a pnnted copy of the conesponding page mstance with the background field value discarded If the page contams a form or is part of a form, then the reset page command is inteφreted as a reset form command A get page status command produces a pnnted report on the status of the conespondmg page mstance, mcludmg who published it, when it was pnnted, for whom it was pnnted, and the status of any forms it contams or is part of The netpage logo which appears on every netpage is usually associated with a duplicate page element When a page mstance is duplicated with field values preserved, field values are pnnted m then native form, l e a checkmark appears as a standard checkmark graphic, and text appears as typeset text Only drawings and signatures appear m then ongmal form, with a signature accompanied by a standard graphic mdicatmg successful signature venfication A duplicate document command produces a pnnted copy of the conespondmg document mstance with background field values preserved If the document contams any forms, then the duplicate document command duplicates the forms m the same way a duplicate form command does A reset document command produces a pnnted copy of the conespondmg document mstance with background field values discarded If the document contams any forms, then the reset document command resets the forms m the same way a reset form command does A get document status command produces a pnnted report on the status of the conespondmg document mstance, mcludmg who published it, when it was pnnted, for whom it was pnnted, and the status of any forms it contams If the page server command's "on selected" attnbute is set, then the command operates on the page identified by the pen's cunent selection rather than on the page contammg the command This allows a menu of page server commands to be pnnted If the target page doesn't contam a page server command element for the designated page server command, then the command is ignored An application can provide application-specific handling by embeddmg the relevant page server command element m a hyperlinked group The page server activates the hyperlink associated with the hyperlinked group rather than executing the page server command A page server command element is hidden if its "hidden" attnbute is set A hidden command element does not have an mput zone on a page and so cannot be activated directly by a user It can, however, be activated via a page server command embedded m a different page, if that page server command has its "on selected" attnbute set 1.8 STANDARD FEATURES OF NETPAGES In the prefened form, each netpage is pnnted with the netpage logo at the bottom to indicate that it is a netpage and therefore has mteractive properties The logo also acts as a copy button In most cases pressmg the logo - 20 - produces a copy of the page In the case of a form, the button produces a copy of the entire form And in the case of a secure document, such as a ticket or coupon, the button elicits an explanatory note or advertismg page The default smgle-page copy function is handled dnectly by the relevant netpage page server Special copy functions are handled by linking the logo button to an application 1.9 USER HELP SYSTEM In a prefened embodiment, the netpage pnnter has a smgle button labelled "Help" When pressed it elicits a smgle page of information, mcludmg • status of pnnter connection • status of pnnter consumables • top-level help menu • document function menu • top-level netpage network dnectory The help menu provides a hierarchical manual on how to use the netpage system The document function menu mcludes the following functions • pπnt a copy of a document • pπnt a clean copy of a form • pπnt the status of a document A document function is initiated by simply pressmg the button and then touching any page of the document The status of a document mdicates who published it and when, to whom it was delivered, and to whom and when it was subsequently submitted as a form The netpage network directory allows the user to navigate the hierarchy of publications and services on the network As an altemative, the user can call the netpage network "900" number "yellow pages" and speak to a human operator The operator can locate the desned document and route it to the user's pnnter Depending on the document type, the publisher or the user pays the small "yellow pages" service fee The help page is obviously unavailable if the pnnter is unable to pnnt In this case the "enor" light is lit and the user can request remote diagnosis over the network 2 PERSONALIZED PUBLICATION MODEL In the following descnption, news is used as a canonical publication example to illustrate personalization mechamsms m the netpage system Although news is often used m the limited sense of newspaper and newsmagazme news, the mtended scope m the present context is wider In the netpage system, the editonal content and the advertismg content of a news publication are personalized usmg different mechamsms The editonal content is personalized according to the reader's explicitly stated and implicitly captured interest profile The advertismg content is personalized according to the reader's locality and demographic 2.1 EDITORIAL PERSONALIZATION A subscnber can draw on two lands of news sources those that deliver news publications, and those that deliver news streams While news publications are aggregated and edited by the publisher, news streams are aggregated either by a news publisher or by a specialized news aggregator News publications typically conespond to traditional newspapers and newsmagazmes, while news streams can be many and vaned a "raw" news feed from a news service, a cartoon stnp, a freelance wnter' s column, a friend' s bulletin board, or the reader's own e-mail The netpage publication server supports the publication of edited news publications as well as the aggregation of multiple news streams By handling the aggregation and hence the formatting of news streams selected - 21 - dnectly by the reader, the server is able to place advertismg on pages over which it otherwise has no editonal control The subscnber builds a daily newspaper by selecting one or more contπbuting news publications, and creatmg a personalized version of each The resulting daily editions are pnnted and bound together mto a smgle newspaper The vanous members of a household typically express then different interests and tastes by selecting different daily publications and then customizing them For each publication, the reader optionally selects specific sections Some sections appear daily, while others appear weekly The daily sections available from The New York Times onlme, for example, mclude "Page One Plus", "National", "International", "Opmion", "Busmess", "Arts/Living", "Technology", and "Sports" The set of available sections is specific to a publication, as is the default subset The reader can extend the daily newspaper by creatmg custom sections, each one drawing on any number of news streams Custom sections might be created for e-mail and friends' announcements ("Personal"), or for monitoring news feeds for specific topics ("Alerts" or "Clippings") For each section, the reader optionally specifies its size, either qualitatively (e g short, medium, or long), or numencally (I e as a limit on its number of pages), and the desned proportion of advertismg, either qualitatively (e g high, normal low, none), or numencally (l e as a percentage) The reader also optionally expresses a preference for a large number of shorter articles or a small number of longer articles Each article is ideally wntten (or edited) m both short and long forms to support this preference An article may also be wntten (or edited) m different versions to match the expected sophistication of the reader, for example to provide children's and adults' versions The appropnate version is selected accordmg to the reader's age The reader can specify a "reading age" which takes precedence over then biological age The articles which make up each section are selected and pπontized by the editors, and each is assigned a useful lifetime By default they are delivered to all relevant subscnbers, in pnonty order, subject to space constraints m the subscnbers' editions In sections where it is appropnate, the reader may optionally enable collaborative filtermg This is then applied to articles which have a sufficiently long lifetime Each article which qualifies for collaborative filtermg is pnnted with rating buttons at the end of the article The buttons can provide an easy choice (e g "liked" and "disliked'), making it more likely that readers will bother to rate the article Articles with high pnonties and short lifetimes are therefore effectively considered essential reading by the editors and are delivered to most relevant subscnbers The reader optionally specifies a serendipity factor, either qualitatively (e g do or don't suφnse me), or numencally A high serendipity factor lowers the threshold used for matchmg during collaborative filtermg A high factor makes it more likely that the conespondmg section will be filled to the reader's specified capacity A different serendipity factor can be specified for different days of the week The reader also optionally specifies topics of particular interest withm a section, and this modifies the pnonties assigned by the editors The speed of the reader's Internet connection affects the quality at which images can be delivered The reader optionally specifies a preference for fewer images or smaller images or both If the number or size of images is not reduced, then images may be delivered at lower quality (l e at lower resolution or with greater compression) At a global level, the reader specifies how quantities, dates, times and monetary values are localized This mvolves specifying whether units are impenal or metnc, a local timezone and time format, and a local cunency, and whether the localization consist of in situ translation or annotation These preferences are denved from the reader's locality by default - 22 - To reduce reading difficulties caused by poor eyesight, the reader optionally specifies a global preference for a larger presentation Both text and images are scaled accordingly, and less information is accommodated on each page The language in which a news publication is published, and its conespondmg text encodmg, is a property of the publication and not a preference expressed by the user However, the netpage system can be configured to provide automatic translation services m vanous guises 2.2 ADVERTISING LOCALIZATION AND TARGETING The personalization of the editonal content dnectly affects the advertismg content, because advertismg is typically placed to exploit the editonal context Travel ads, for example, are more likely to appear m a travel section than elsewhere The value of the editonal content to an advertiser (and therefore to the publisher) lies m its ability to attract large numbers of readers with the nght demographics Effective advertising is placed on the basis of locality and demographics Locality determmes proximity to particular services, retailers etc , and particular mterests and concerns associated with the local community and envnonment Demographics determme general interests and preoccupations as well as likely spendmg patterns A news publisher's most profitable product is advertismg "space", a multi-dimensional entity determined by the publication's geographic coverage, the size of its readership, its readership demographics, and the page area available for advertismg In the netpage system, the netpage publication server computes the approximate multi-dimensional size of a publication's saleable advertismg space on a per-section basis, taking mto account the publication's geographic coverage, the section's readership, the size of each reader's section edition, each reader's advertismg proportion, and each reader's demographic In companson with other media, the netpage system allows the advertismg space to be defined in greater detail, and allows smaller pieces of it to be sold separately It therefore allows it to be sold at closer to its true value For example, the same advertismg "slot" can be sold m varying proportions to several advertisers, with mdividual readers' pages randomly receivmg the advertisement of one advertiser or another, overall preservmg the proportion of space sold to each advertiser The netpage system allows advertismg to be linked dnectly to detailed product information and onlme purchasing It therefore raises the intrinsic value of the advertismg space Because personalization and localization are handled automatically by netpage publication servers, an advertismg aggregator can provide arbitranly broad coverage of both geography and demographics The subsequent disaggregation is efficient because it is automatic This makes it more cost-effective for publishers to deal with advertismg aggregators than to directly capture advertismg Even though the advertismg aggregator is taking a proportion of advertismg revenue, publishers may find the change profit-neutral because of the greater efficiency of aggregation The advertismg aggregator acts as an intermediary between advertisers and publishers, and may place the same advertisement m multiple publications It is worth noting that ad placement m a netpage publication can be more complex than ad placement m the publication's traditional counteφart, because the publication's advertismg space is more complex While ignoring the full complexities of negotiations between advertisers, advertismg aggregators and publishers, the prefened form of the netpage system provides some automated support for these negotiations, mcludmg support for automated auctions of advertismg space Automation is particularly desnable for the placement of advertisements which generate small amounts of mcome, such as small or highly localized advertisements Once placement has been negotiated, the aggregator captures and edits the advertisement and records it on a - 23 - netpage ad server Conespondmgly, the publisher records the ad placement on the relevant netpage publication server When the netpage publication server lays out each user's personalized publication, it picks the relevant advertisements from the netpage ad server 2.3 USER PROFILES 2.3.1 Information Filtering The personalization of news and other publications relies on an assortment of user-specific profile nformation, mcludmg publication customizations collaborative filtermg vectors • contact details presentation preferences The customization of a publication is typically publication-specific, and so the customization information is mamtamed by the relevant netpage publication server A collaborative filtermg vector consists of the user's ratings of a number of news items It is used to conelate different users' interests for the p nposes of making recommendations Although there are benefits to mamtainmg a smgle collaborative filtermg vector mdependenfly of any particular publication, there are two reasons why it is more practical to maintain a separate vector for each publication there is likely to be more overlap between the vectors of subscnbers to the same publication than between those of subscnbers to different publications, and a publication is likely to want to present its users' collaborative filtermg vectors as part of the value of its brand, not to be found elsewhere Collaborative filtermg vectors are therefore also mamtamed by the relevant netpage publication server Contact details, mcludmg name, street address, ZIP Code, state, country, telephone numbers, are global by nature, and are mamtamed by a netpage registration server Presentation preferences, mcludmg those for quantities, dates and times, are likewise global and mamtamed m the same way The localization of advertismg relies on the locality indicated m the user's contact details, while the targeting of advertismg relies on personal information such as date of birth, gender, mantal status, mcome, profession, education, or qualitative denvatives such as age range and mcome range For those users who choose to reveal personal information for advertismg pinposes, the information is mamtamed by the relevant netpage registration server In the absence of such information, advertismg can be targeted on the basis of the demographic associated with the user's ZIP or ZIP+4 Code Each user, pen, pnnter, application provider and application is assigned its own umque identifier, and the netpage registration server maintains the relationships between them, as shown m Figures 21, 22, 23 and 24 For registration puφoses, a publisher is a special land of application provider, and a publication is a special land of application Each user 800 may be authorized to use any number of pnnters 802, and each pnnter may allow any number of users to use it Each user has a smgle default pnnter (at 66), to which penodical publications are delivered by default, whilst pages pnnted on demand are delivered to the pnnter through which the user is mteractmg The server keeps track of which publishers a user has authorized to pnnt to the user's default pπnter A publisher does not record the ID of any particular pπnter, but mstead resolves the ID when it is reqiured When a user subscnbes 808 to a publication 807, the publisher 806 (1 e application provider 803) is authorized to pπnt to a specified pnnter or the user's default pnnter This authorization can be revoked at any time by the user Each user may have several pens 801, but a pen is specific to a smgle user If a user is authorized to use a - 24 - particular pnnter, then that pnnter recognizes any of the user's pens The pen ID is used to locate the conespondmg user profile mamtamed by a particular netpage registration server, via the DNS m the usual way A Web terminal 809 can be authorized to pπnt on a particular netpage pnnter, allowing Web pages and netpage documents encountered during Web browsmg to be conveniently pnnted on the nearest netpage pπnter The netpage system can collect, on behalf of a pπnter provider, fees and commissions on mcome earned through publications pnnted on the provider's pnnters Such mcome can mclude advertismg fees, click-through fees, e- commerce commissions, and transaction fees If the pπnter is owned by the user, then the user is the pnnter provider Each user also has a netpage account 820 which is used to accumulate micro-debits and credits (such as those descnbed in the precedmg paragraph), contact details 815, mcludmg name, address and telephone numbers, global preferences 816, mcludmg pnvacy, delivery and localization settings, any number of biometπc records 817, contammg the user's encoded signature 818, fingeφnnt 819 etc, a handwnting model 819 automatically mamtamed by the system, and SET payment card accounts 821 with which e-commerce payments can be made 2.3.2 Favorites List A netpage user can maintain a list 922 of "favontes" - links to useful documents etc on the netpage network The list is mamtamed by the system on the user's behalf It is organized as a hierarchy of folders 924, a prefemed embodiment of which is shown m the class diagram m Figure 41 2.3.3 History List The system maintains a history list 929 on each user's behalf, contammg links to documents etc accessed by the user through the netpage system It is organized as a date-ordered list, a prefened embodiment of which is shown m the class diagram in Figure 42 2.4 INTELLIGENT PAGE LAYOUT The netpage publication server automatically lays out the pages of each user's personalized publication on a section-by-section basis Smce most advertisements are m the form of pre-formatted rectangles, they are placed on the page before the editonal content The advertismg ratio for a section can be achieved with wildly varying advertismg ratios on mdividual pages within the section, and the ad layout algonthm exploits this The algonthm is configured to attempt to co-locate closely tied editonal and advertismg content, such as placmg ads for roofing matenal specifically withm the publication because of a special feature on do-it-yourself roofing repans The editonal content selected for the user, mcludmg text and associated images and graphics, is then laid out according to vanous aesthetic rules The entire process, mcludmg the selection of ads and the selection of editonal content, must be iterated once the layout has converged, to attempt to more closely achieve the user's stated section size preference The section size preference can, however, be matched on average over time, allowing significant day-to-day vanations 2.5 DOCUMENT FORMAT Once the document is laid out, it is encoded for efficient distnbution and persistent storage on the netpage network The primary efficiency mechanism is the separation of information specific to a smgle user's edition and information shared between multiple users' editions The specific information consists of the page layout The shared information consists of the objects to which the page layout refers, mcludmg images, graphics, and pieces of text A text object contams fully-formatted text represented m the Extensible Markup Language (XML) usmg the Extensible Stylesheet Language (XSL) XSL provides precise control over text formatting mdependenfly of the region - 25 - mto which the text is bemg set, which m this case is bemg provided by the layout The text object contams embedded language codes to enable automatic translation, and embedded hyphenation hints to aid with paragraph formatting An image object encodes an image m the JPEG 2000 wavelet-based compressed image format A graphic object encodes a 2D graphic m Scalable Vector Graphics (SVG) format The layout itself consists of a senes of placed image and graphic objects, linked textflow objects through which text objects flow, hyperlinks and mput fields as descπbed above, and watermark regions These layout objects are summarized m Table 3 The layout uses a compact format suitable for efficient distπbution and storage Table 3 - netpage layout objects 2.6 DOCUMENT DISTRIBUTION As descnbed above, for pinposes of efficient distnbution and persistent storage on the netpage network, a user-specific page layout is separated from the shared objects to which it refers When a subscnbed publication is ready to be distnbuted, the netpage publication server allocates, with the help of the netpage ID server 12, a umque ID for each page, page mstance, document, and document mstance The server computes a set of optimized subsets of the shared content and creates a multicast channel for each subset, and then tags each user-specific layout with the names of the multicast channels which will carry the shared content used by that layout The server then pointcasts each user's layouts to that user's pnnter via the appropnate page server, and when the pointcastmg is complete, multicasts the shared content on the specified channels After receivmg its pomtcast, each page server and pnnter subscnbes to the multicast channels specified m the page layouts During the multicasts, each page server and pnnter extracts from the multicast streams those objects refened to by its page layouts The page servers persistently archive the received page layouts and shared content Once a pnnter has received all the objects to which its page layouts refer, the pπnter re-creates the fully- populated layout and then rasteπzes and pnnts it Under normal cncumstances, the pnnter pnnts pages faster than they can be delivered Assuming a quarter of each page is covered with images, the average page has a size of less than 400KB The pπnter can therefore hold m - 26 - excess of 100 such pages m its mtemal 64MB memory, allowmg for temporary buffers etc The pπnter pnnts at a rate of one page per second This is eqmvalent to 400KB or about 3Mbit of page data per second, which is similar to the highest expected rate of page data delivery over a broadband network Even under abnormal cncumstances, such as when the pnnter runs out of paper, it is likely that the user will be able to replemsh the paper supply before the pnnter' s 100-page mtemal storage capacity is exhausted However, if the pnnter' s mtemal memory does fill up, then the pnnter will be unable to make use of a multicast when it first occurs The netpage publication server therefore allows pnnters to submit requests for re- multicasts When a cntical number of requests is received or a timeout occurs, the server re-multicasts the conespondmg shared objects Once a document is pnnted, a pπnter can produce an exact duplicate at any time by retnevmg its page layouts and contents from the relevant page server 2.7 ON-DEMAND DOCUMENTS When a netpage document is requested on demand, it can be personalized and delivered m much the same way as a penodical However, smce there is no shared content, delivery is made dnectly to the requesting pnnter without the use of multicast When a non-netpage document is requested on demand, it is not personalized, and it is delivered via a designated netpage formatting server which reformats it as a netpage document A netpage formatting server is a special mstance of a netpage publication server The netpage formatting server has knowledge of vanous Internet document formats, mcludmg Adobe's Portable Document Format (PDF), and Hypertext Markup Language (HTML) In the case of HTML, it can make use of the higher resolution of the pnnted page to present Web pages m a multi-column format, with a table of contents It can automatically mclude all Web pages dnectly linked to the requested page The user can tune this behavior via a preference The netpage formatting server makes standard netpage behavior, mcludmg interactivity and persistence, available on any Internet document, no matter what its ongm and format It hides knowledge of different document formats from both the netpage pnnter and the netpage page server, and hides knowledge of the netpage system from Web servers 3 SECURITY 3.1 CRYPTOGRAPHY Cryptography is used to protect sensitive information, both m storage and m transit, and to authenticate parties to a transaction There are two classes of cryptography m widespread use secret-key cryptography and public-key cryptography The netpage network uses both classes of cryptography Secret-key cryptography, also refened to as symmetnc cryptography, uses the same key to encrypt and decrypt a message Two parties wishing to exchange messages must first anange to securely exchange the secret key Public-key cryptography, also refened to as asymmetnc cryptography, uses two encryption keys The two keys are mathematically related m such a way that any message encrypted usmg one key can only be decrypted usmg the other key One of these keys is then published, while the other is kept pnvate The public key is used to encrypt any message mtended for the holder of the pnvate key Once encrypted usmg the public key, a message can only be decrypted usmg the pnvate key Thus two parties can securely exchange messages without first havmg to exchange a secret key To ensure that the pnvate key is secure, it is normal for the holder of the pnvate key to generate the key pan Public-key cryptography can be used to create a digital signature The holder of the pnvate key can create a known hash of a message and then encrypt the hash usmg the pnvate key Anyone can then venfy that the encrypted hash constitutes the "signature" of the holder of the pnvate key with respect to that particular message by decrypting the - 27 - encrypted hash usmg the public key and venfying the hash against the message If the signature is appended to the message, then the recipient of the message can venfy both that the message is genume and that it has not been altered m transit To make public-key cryptography work, there has to be a way to distnbute public keys which prevents impersonation This is normally done usmg certificates and certificate authonties A certificate authonfy is a trusted third party which authenticates the connection between a public key and someone's identity The certificate authonty venfies the person's identity by examining identify documents, and then creates and signs a digital certificate contammg the person's identity details and public key Anyone who trusts the certificate authonty can use the public key m the certificate with a high degree of certainty that it is genume They just have to venfy that the certificate has mdeed been signed by the certificate authonfy, whose public key is well-known In most transaction envnonments, public-key cryptography is only used to create digital signatures and to securely exchange secret session keys Secret-key cryptography is used for all other pinposes In the following discussion, when reference is made to the secure transmission of information between a netpage pnnter and a server, what actually happens is that the pnnter obtains the server's certificate, authenticates it with reference to the certificate authonfy, uses the public key-exchange key m the certificate to exchange a secret session key with the server, and then uses the secret session key to encrypt the message data A session key, by definition, can have an arbifranly short lifetime 3.2 NETPAGE PRINTER SECURITY Each netpage pnnter is assigned a pan of umque identifiers at time of manufacture which are stored m read-only memory m the pπnter and m the netpage registration server database The pπnter ID 62 is public and umquely identifies the pnnter on the netpage network The secret ID 90 is secret and is used when the pnnter is first registered on the network A prefened embodiment of a pnnter registration protocol is shown m Figure 50 Accordmg to the protocol, when the pnnter connects to the netpage network for the first time after installation, it creates a signature pubhc/pπvate key pan 91,92 It transmits the secret ID and the public key 91 securely to the netpage registration server 11 The server compares the secret ID against the printer's secret ID recorded m its database 74, and accepts the registration if the IDs match It then creates and signs a certificate contammg the pnnter' s public ID and public signature key, and stores the certificate m the registration database The pπnter stores its pnvate key 92 m its flash memory 81 When the pnnter needs to exchange a session key with a server, it generates a random session key, signs it usmg its pnvate signature key 92, and securely transmits the session key to the server, 1 e encrypted usmg the server's public key-exchange key from the server's certificate The server venfies that the pπnter is a registered netpage pπnter by venfying the signature usmg the pπnter' s public signature key from the pπnter' s certificate, available from the registration server The netpage registration server can act as a certificate authonfy for the pnnter smce it has pnveleged access to secret information allowing it to venfy pnnter identify As an alternative to the pnnter generating the signature pubhc/pnvate key pan when it registers, the pnvate key 92 can be stored m the pπnter' s ROM at time of manufacture and the matchmg public key 91 stored m the registration server database at time of manufacture, obviating the need for the secret ID 90 As another alternative, pnnter registration can utilize the same technique used for pen registration, as descnbed below 3.2.1 Publisher Authorization When a user subscnbes to a publication, a record 808 is created m the netpage registration server database authorizing the publisher to pnnt the publication to the user's default pπnter or a specified pπnter Every document 836 - 28 - sent to a pnnter via a page server is addressed to a particular user, via the user's alias ID 65 with respect to the publisher, and is signed by the publisher usmg the publisher's pnvate signature key The page server veπfies, via the registration database, that the publisher 803,806 is authorized to deliver the publication to the specified user 805 The page server venfies the signature usmg the publisher's public key, obtamed from the publisher's certificate 67 stored m the registration database The netpage registration server accepts a request to add a prmtmg authorization m the form of a subscnption 808 to the database, so long as the request is initiated via a pen registered, via a user, to the pπnter through which the request is initiated 3.2.2 Web Terminal Authorization The user can authorize a Web terminal to pπnt on a pnnter This is useful if the user has a Web terminal m the home which is used to locate documents on the Web for printing A prefened embodiment of a Web terminal authorization protocol is shown in Figure 51 According to the protocol, the one-time authorization proceeds as follows the user requests a Web terminal authorization page via the pnnter 601 The netpage registration server generates a short-lifetime one-tune-use authorization ID 412 for the Web terminal which is pnnted on the authorization page 413, together with the URI of the pnnter The Web terminal 75 is used to navigate to a netpage registration server registration Web site, where the authorization ID is entered, as well as the URI of the pπnter The Web terminal generates a signature pubhc/pnvate key pan 95,96, and transmits the public key 95 to the regisfration server The server allocates a terminal ID 68 for the Web terminal, and stores an authorization record 809 m the registration server database linked to the pπnter and contammg the terminal ID and public key The URI of the pπnter, the Web terminal's terminal ID, and the pnvate signature key 96 are stored locally m the Web terminal's database 76 A prefened embodiment of a Web terminal pπnting protocol is shown m Figure 52 Accordmg to the protocol, whenever the Web terminal 75 wishes to pπnt on the pπnter 601, it sends the printer's designated netpage formatting server 77 a request contammg the URI of the document to be pnnted, together with the terminal ID 68 It attches a digital signature 418 to the request, created usmg the Web termmars pnvate signature key 96 On receipt of the request and before acting on it, the formatting server venfies, via the registration server 11, that the terminal is authorized to pπnt on the specified pnnter The registration server venfies, via the Web terminal record 809 in the registration server database, that the terminal is authorized to pnnt to the pπnter, and venfies the digital signature usmg the terminal's public key 95 The user can pnnt a list of cunent printing authorizations at any time, and revoke any which are bemg abused 3.3 NETPAGE PEN SECURITY Each netpage pen is assigned a umque identifier at time of manufacture which is stored m read-only memory m the pen and m the netpage registration server database The pen ID 61 umquely identifies the pen on the netpage network A netpage pen can "know" a number of netpage pnnters, and a prmter can "know" a number of pens A pen commumcates with a pπnter via a radio frequency signal whenever it is withm range of the pnnter Once a pen and pnnter are registered, they regularly exchange session keys Whenever the pen transmits digital ink to the pnnter, the digital ink is always encrypted usmg the appropnate session key Digital ink is never transmitted m the clear A pen stores a session key for every pnnter it knows, mdexed by pnnter ID, and a pnnter stores a session key for every pen it knows, mdexed by pen ID Both have a large but fimte storage capacify for session keys, and will forget a session key on a least-recently-used basis if necessary A prefened embodiment of a pen connection protocol is shown m Figure 53 According to the protocol, - 29 - when a pen 101 comes withm range of a pnnter 601, the pen and pnnter discover whether they already know each other If they don't know each other, then the pπnter determmes, via the registration server 11 , whether it is supposed to know the pen This might be, for example, because the pen belongs to a user who is registered to use the pnnter The pπnter sends its own pnnted ID 62, together with the pen ID, to the registration server The registration server determmes if a pnnter record 802 and a pen record 801 are linked to the same user record 800 m the registration server database 74 If the pnnter is meant to know the pen but doesn't, then it mitiates the automatic pen registration procedure descnbed below If the pnnter isn't meant to know the pen, then it agrees with the pen to ignore it until the pen is placed in a charging cup, at which tune it mitiates the registration procedure In addition to its public pen ID 61, the pen contams a secret key-exchange key 93 The key-exchange key is recorded m the netpage registration server database at time of pen manufacture A prefened embodiment of a pen registration protocol is shown m Figure 54 According to the protocol, the pen 101 transmits its pen ID to the pnnter 601 The pπnter responds with a nonce 423, a random or seπally-allocated one-time-use number The pen encrypts the nonce usmg its key-exchange key, and returns the encrypted nonce 424 to the pnnter The pnnter transmits the pen ID, nonce and encrypted nonce to the netpage registration server 11 The server venfies, by decrypting the nonce usmg the pen's key-exchange key stored in the registration server database 74, that the pen knows the key-exchange key The server then generates a session key 94 for the pnnter and pen to use, and securely transmits the session key to the pnnter It also transmits a copy 425 of the session key encrypted usmg the pen's key-exchange key The pπnter stores the session key m its flash memory 81, mdexed by pen ID, and transmits the encrypted session key to the pen The pen stores the session key m its flash memory 83, mdexed by pπnter ID When a previously unregistered pen is first registered, it is of limited use until it is linked to a user A registered but "un-owned" pen is only allowed to be used to request and fill in netpage user and pen registration forms, to register a new user to which the new pen is automatically linked, or to add a new pen to an existing user The pen uses secret-key rather than public-key encryption because of hardware performance constraints m the pen 3.4 SECURE DOCUMENTS The netpage system supports the delivery of secure documents such as tickets and coupons The netpage pnnter mcludes a facility to pπnt watermarks, but will only do so on request from publishers who are suitably authorized The publisher mdicates its authonfy to pπnt watermarks its certificate, which the pπnter is able to authenticate The "watermark" prmtmg process uses an alternative dither matπx m specified "watermark" regions of the page Back-to-back pages contam mirror-image watermark regions which comcide when pnnted The dither matnces used m odd and even pages' watermark regions are designed to produce an interference effect when the regions are viewed together, achieved by looking through the pnnted sheet The effect is similar to a watermark m that it is not visible when looking at only one side of the page, and is lost when the page is copied by normal means Pages of secure documents cannot be copied usmg the built-in netpage copy mechanism descnbed m Section 1 9 above This extends to copymg netpages on netpage-aware photocopiers Secure documents are typically generated as part of e-commerce transactions They can therefore mclude the user's photograph which was captured when the user registered biometnc mf ormation with the netpage registration server, as descnbed m Section 2 When presented with a secure netpage document, the recipient can venfy its authenticity by requesting its status m the usual way The umque ID of a secure document is only valid for the lifetime of the document, and secure - 30 - document IDs are allocated non-contiguously to prevent then prediction by opportimistic forgers A secure document venfication pen can be developed with bmlt-m feedback on venfication failure, to support easy pomt-of-presentation document venfication Clearly neither the watermark nor the user's photograph are secure m a cryptographic sense They simply provide a sigmficant obstacle to casual forgery Onlme document venfication, particularly usmg a venfication pen, provides an added level of secunfy where it is needed, but is still not entirely immune to forgenes 3.5 NON-REPUDIATION In the netpage system, forms submitted by users are delivered reliably to forms handlers and are persistently archived on netpage page servers It is therefore impossible for recipients to repudiate delivery E-commerce payments made through the system, as descnbed m Section 4, are also impossible for the payee to repudiate 4 ELECTRONIC COMMERCE MODEL 4.1 SECURE ELECTRONIC TRANSACTION (SET) The netpage system uses the Secure Electromc Transaction (SET) system as one of its payment systems SET, havmg been developed by MasterCard and Visa, is organized around payment cards, and this is reflected m the terminology However, much of the system is mdependent of the type of accounts bemg used In SET, cardholders and merchants register with a certificate authonty and are issued with certificates containing then public signature keys The certificate authonfy venfies a cardholder's registration details with the card issuer as appropnate, and venfies a merchant's registration details with the acquner as appropnate Cardholders and merchants store then respective pnvate signature keys securely on then computers During the payment process, these certificates are used to mutually authenticate a merchant and cardholder, and to authenticate them both to the payment gateway SET has not yet been adopted widely, partly because cardholder maintenance of keys and certificates is considered burdensome Interim solutions which maintain cardholder keys and certificates on a server and give the cardholder access via a password have met with some success 4.2 SET PAYMENTS In the netpage system the netpage registration server acts as a proxy for the netpage user (l e the cardholder) m SET payment transactions The netpage system uses biometπcs to authenticate the user and authorize SET payments Because the system is pen-based, the biometπc used is the user's on-lme signature, consisting of time- varying pen position and pressure A fingeφnnt biometnc can also be used by designing a fingeφnnt sensor mto the pen, although at a higher cost The type of biometnc used only affects the capture of the biometnc, not the authorization aspects of the system The first step to bemg able to make SET payments is to register the user's biometnc with the netpage registration server This is done m a controlled environment, for example a bank, where the biometnc can be captured at the same time as the user's identify is venfied The biometnc is captured and stored m the registration database, linked to the user's record The user's photograph is also optionally captured and linked to the record The SET cardholder registration process is completed, and the resulting pnvate signature key and certificate are stored m the database The user's payment card information is also stored, giving the netpage regisfration server enough information to act as the user's proxy in any SET payment transaction When the user eventually supplies the biometnc to complete a payment, for example by signing a netpage order form, the pnnter securely transmits the order information, the pen ID and the biometnc data to the netpage registration server The server venfies the biometnc with respect to the user identified by the pen ID, and from then on - 31 - acts as the user's proxy m completmg the SET payment transaction 4.3 MICRO-PAYMENTS The netpage system mcludes a mechanism for micro-payments, to allow the user to be convemently charged for prmtmg low-cost documents on demand and for copymg copynght documents, and possibly also to allow the user to be reimbursed for expenses mcuned m pπnting advertismg matenal The latter depends on the level of subsidy already provided to the user When the user registers for e-commerce, a network account is established which aggregates micro- payments The user receives a statement on a regular basis, and can settle any outstandmg debit balance usmg the standard payment mechanism The network account can be extended to aggregate subscnption fees for penodicals, which would also otherwise be presented to the user m the form of mdividual statements 4.4 TRANSACTIONS When a user requests a netpage m a particular application context, the application is able to embed a user- specific transaction ID 55 m the page Subsequent mput through the page is tagged with the transaction ID, and the application is thereby able to establish an appropnate context for the user' s mput When mput occurs through a page which is not user-specific, however, the application must use the user's umque identity to establish a context A typical example mvolves adding items from a pre-pπnted catalog page to the user's virtual "shopping cart" To protect the user's pnvacy, however, the umque user ID 60 known to the netpage system is not divulged to applications This is to prevent different application providers from easily conelating mdependenfly accumulated behavioral data The netpage registration server mstead maintains an anonymous relationship between a user and an application via a umque alias ID 65, as shown m Figure 24 Whenever the user activates a hyperlink tagged with the "registered" attnbute, the netpage page server asks the netpage registration server to translate the associated application ID 64, together with the pen ID 61, mto an alias ID 65 The alias ID is then submitted to the hyperlink's application The application maintains state information mdexed by alias ID, and is able to retneve user-specific state information without knowledge of the global identify of the user The system also maintains an mdependent certificate and pnvate signature key for each of a user's applications, to allow it to sign application transactions on behalf of the user usmg only application-specific information To assist the system m routing product bar code (UPC) "hyperlink" activations, the system records a favoπte application on behalf of the user for any number of product types Each application is associated with an application provider, and the system maintains an account on behalf of each application provider, to allow it to credit and debit the provider for click-through fees etc An application provider can be a publisher of penodical subscnbed content The system records the user's willingness to receive the subscnbed publication, as well as the expected frequency of publication. 4.5 RESOURCE DESCRIPTIONS AND COPYRIGHT A prefened embodiment of a resource descnption class diagram is shown m Figure 40 Each document and content object may be descnbed by one or more resource descnptions 842 Resource descnptions use the Dublin Core metadata element set, which is designed to facilitate discovery of electromc resources Dublm Core metadata conforms to the World Wide Web Consortium (W3C) Resource Descnption Framework (RDF) A resource descnption may identify nghts holders 920 The netpage system automatically transfers copynght fees from users to nghts holders when users pnnt copynght content - 32 - 5 COMMUNICATIONS PROTOCOLS A commumcations protocol defines an ordered exchange of messages between entities In the netpage system, entities such as pens, pnnters and servers utilise a set of defined protocols to cooperatively handle user mteraction with the netpage system Each protocol is illustrated by way of a sequence diagram m which the horizontal dimension is used to represent message flow and the vertical dimension is used to represent time Each entify is represented by a rectangle contammg the name of the entify and a vertical column representing the lifeline of the entify During the time an entify exists, the lifeline is shown as a dashed lme During the time an entity is active, the lifeline is shown as a double lme Because the protocols considered here do not create or destroy entities, lifelmes are generally cut short as soon as an entity ceases to participate m a protocol 5.1 SUBSCRIPTION DELIVERY PROTOCOL A large number of users may subscπbe to a penodical publication Each user's edition may be laid out differently, but many users' editions will share common content such as text objects and image objects The subscnption delivery protocol therefore delivers document structures to mdividual pnnters via pomtcast, but delivers shared content objects via multicast A prefened embodiment of a subscnption delivery protocol is shown m Figure 43 Accordmg to the protocol, the application (I e publisher) first obtains a document ID 51 for each document from an ID server 12 It then sends each document structure 836, mcludmg its document ID and page descnptions 5, to the page server 10 responsible for the document's newly allocated ID It mcludes its own application ID 64, the subscπber's alias ID 65, and the relevant set of multicast channel names 402 It attaches a digital signature 401 to the message, created usmg its pnvate signature key The page server uses the application ID and alias ID to obtain from the registration server 11 the conesponding user ID 60, the user's selected pnnter ID 62 (which may be explicitly selected for the application, or may be the user's default pnnter), and the application's certificate 67 The application's certificate allows the page server to venfy the message signature 401 The page server's request to the registration server fails if the application ID and alias ID don't together identify a subscnption 808 The page server then allocates document and page mstance IDs and forwards the page descnptions 5, mcludmg page IDs 50, to the pnnter It mcludes the relevant set of multicast channel names for the pnnter to listen to It then returns the newly allocated page IDs to the application for future reference Once the application has distπbuted all of the document structures to the subscnbers' selected pnnters via the relevant page servers, it multicasts the vanous subsets of the shared objects 405 on the previously selected multicast channels Both page servers and pnnters monitor the appropnate multicast channels and receive then requned content objects They are then able to populate the previously pomtcast document structures 400,404 This allows the page servers to add complete documents to then databases, and it allows the pnnters to pπnt the documents 5.2 HYPERLINK ACTIVATION PROTOCOL A prefened embodiment of a hyperlink activation protocol is shown m Figure 45 Accordmg to the protcol, when a user clicks on a netpage with a netpage pen, the pen commumcates the click 406 to the nearest netpage pπnter 601 The click identifies the page and a location on the page The pnnter already knows the pen ID 61 of the pen from the pen connection protocol The pnnter determmes, via the DNS, the network address of the page server 10a handling the particular page ID 50 The address may already be m its cache if the user has recently mteracted with the same page The pπnter then forwards the pen ID, its own pπnter ID 62, the page ID and click location to the page server - 33 - The page server loads the page descnption 5 identified by the page ID and determmes which mput element's zone 58, if any, the click lies m Assummg the relevant mput element is a hyperlmk element 844, the page server then obtams the associated application ID 64 and lmk ID 54, and determmes, via the DNS, the network address of the application server hosting the application 71 The page server uses the pen ID 61 to obtain the conespondmg user ID 60 from the registration server 11, and then allocates a globally umque hyperlink request ID 52 and builds a hyperlink request 934 The hyperlink request class diagram is shown m Figure 44 The hyperlink request records the IDs of the requesting user and pnnter, and identifies the clicked hyperlink mstance 862 The page server then sends its own server ID 53, the hyperlink request ID, and the link ID to the application The application produces a response document according to application-specific logic, and obtams a document ID 51 from an ID server 12 It then sends the document 836 to the page server 10b responsible for the document's newly allocated ID, together with the requesting page server's ID and the hyperlink request ID The second page server sends the hyperlink request ID and application ID to the first page server 10a to obtain the conesponding user ID and pnnter ID 62 The first page server rejects the request if the hyperlink request has expired or is for a different application The second page server allocates a document mstance ID and page IDs 50, returns the newly allocated page IDs to the application, adds the complete document to its own database, and finally sends the page descnptions 5 to the requesting pnnter The hyperlink mstance may mclude a meaningful transaction ID 55, m which case the first page server mcludes the transaction ID m the message sent to the application This allows the application to establish a transaction- specific context for the hyperlink activation If the hyperlink requnes a user alias, i e its "alias required" attnbute is set, then the first page server 10a sends both the pen ID 61 and the hyperlink's application ID 64 to the registration server 11 to obtain not just the user ID conesponding to the pen ID but also the alias ID 65 conesponding to the application ID and the user ID It mcludes the alias ID m the message sent to the application, allowing the application to establish a user-specific context for the hyperlink activation 5.3 HANDWRITING RECOGNITION PROTOCOL A prefened embodiment of a handwriting recogmtion protocol is shown in Figure 46 According to the protocol, when a user draws a sfroke on a netpage with a netpage pen, the pen commumcates the stroke 406 to the nearest netpage pπnter The stroke identifies the page and a path on the page The pπnter forwards the pen ID 61, its own pπnter ID 62, the page ID 50 and stroke path to the page server 10 m the usual way The page server loads the page descnption 5 identified by the page ID and determmes which mput element's zone 58, if any, the stroke mtersects Assummg the relevant mput element is a text field 878, the page server appends the stroke to the text field's digital ink After a penod of inactivity m the zone of the text field, the page server sends the pen ID and the pendmg digital ink 407 to the registration server 11 for mteφretation It may also send the existing text value 408 of the text field to allow the registration server to handle hand-drawn editing commands such as stnke-outs The registration server identifies the user conespondmg to the pen, and uses the user's accumulated handwnting model 822 to mteφret the sfrokes as handwritten text Once it has converted the strokes to text, the regisfration server returns the converted text 409 to the requesting page server The page server appends the text to the text value of the text field 5.4 SIGNATURE VERIFICATION PROTOCOL A prefened embodiment of a signature venfication protocol is shown m Figure 47 Accordmg to the protocol, a stroke is delivered to a page-specific page server m the same way as descnbed m Section 5 3 Assummg the - 34 - mput element whose zone the stroke 406 mtersects is a signature field 880, the page server 10 appends the stroke to the signature field's digital ink After a penod of inactivity m the zone of the signature field, the page server sends the pen ID 61 and the pendmg digital ink 407 to the registration server 11 for venfication It also sends the application ID 64 associated with the form of which the signature field is part, as well as the form ID 56 and the current data content 405 of the form The registration server identifies the user conesponding to the pen, and uses the user's dynamic signature biometnc 818 to venfy the sfrokes as the user's signature Once it has venfied the signature, the regisfration server uses the application ID 64 and user ID 60 to identify the user's application-specific pnvate signature key It then uses the key to generate a digital signature of the form data, and returns the digital signature 410 to the requesting page server The page server assigns the digital signature to the signature field and sets the associated form's status to frozen The digital signature mcludes the alias ID 65 of the conespondmg user This allows a smgle form to capture multiple users' signatures 5.5 FORM SUBMISSION PROTOCOL Form submission occurs via a form hyperlink activation A prefened embodiment of a form submission protocol is shown m Figure 48 It follows the protocol defined m Section 5 2, with some form-specific additions In the case of a form hyperlink, the hyperlink activation message sent by the page server 10 to the application 71 also contams the form ID 56 and the cunent data content of the form If the form contams any signature fields, then the application veπfies each one by extracting the alias ID 65 associated with the conesponding digital signature and obtaining the conespondmg certificate from the regisfration server 11 5.6 COMMISSION PAYMENT PROTOCOL In an e-commerce envnonment, fees and commissions may be payable from an application provider to a publisher on click-throughs, transactions and sales Commissions on fees and commissions on commissions may also be payable from the publisher to the provider of the pnnter A prefened embodiment of a commission payment protocol is shown m Figure 49 Accordmg to the protocol, the hyperlink request ID 52 is used to route a fee or commission credit from the target application provider 70a (e g merchant) to the source application provider 70b (l e publisher), and from the source application provider 70b to the pnnter provider 72 The target application receives the hyperlink request ID from the page server 10 when the hyperlink is first activated, as descnbed m Section 5 2 When the target application needs to credit the source application provider, it sends the application provider credit 414 to the ongmal page server together with the hyperlink request ID The page server uses the hyperlink request ID to identify the source application, and sends the credit on to the relevant regisfration server 11 together with the source application ID 64, its own server ID 53, and the hyperlink request ID The registration server credits the conesponding application provider's account 827 It also notifies the application provider If the application provider needs to credit the pnnter provider, it sends the pnnter provider credit 415 to the ongmal page server together with the hyperlink request ID The page server uses the hyperlink request ID to identify the pπnter, and sends the credit on to the relevant registration server together with the pnnter ID The regisfration server credits the conespondmg pnnter provider account 814 The source application provider is optionally notified of the identify of the target application provider, and the pnnter provider of the identify of the source application provider 6. NETPAGE PEN DESCRIPTION 6.1 PEN MECHANICS Referring to Figures 8 and 9, the pen, generally designated by reference numeral 101, mcludes a housmg - 35 - 102 m the form of a plastics moulding havmg walls 103 defining an mtenor space 104 for mounting the pen components The pen top 105 is m operation rotatably mounted at one end 106 of the housmg 102 A semi-transparent cover 107 is secured to the opposite end 108 of the housmg 102 The cover 107 is also of moulded plastics, and is formed from semi-transparent matenal m order to enable the user to view the status of the LED mounted withm the housmg 102 The cover 107 mcludes a mam part 109 which substantially sunounds the end 108 of the housmg 102 and a projecting portion 110 which projects back from the mam part 109 and fits withm a conesponding slot 111 formed m the walls 103 of the housmg 102 A radio antenna 112 is mounted behind the projecting portion 110, withm the housmg 102 Screw threads 113 suπounding an aperture 113A on the cover 107 are ananged to receive a metal end piece 114, mcludmg conespondmg screw threads 115 The metal end piece 114 is removable to enable ink cartridge replacement Also mounted withm the cover 107 is a tπ-color status LED 116 on a flex PCB 117 The antenna 112 is also mounted on the flex PCB 117 The status LED 116 is mounted at the top of the pen 101 for good all-around visibility The pen can operate both as a normal markmg ink pen and as a non-marking stylus An mk pen cartridge 118 with mb 119 and a stylus 120 with stylus mb 121 are mounted side by side withm the housmg 102 Either the ink cartridge mb 119 or the stylus mb 121 can be brought forward through open end 122 of the metal end piece 114, by rotation of the pen top 105 Respective slider blocks 123 and 124 are mounted to the ink cartndge 118 and stylus 120, respectively A rotatable cam banel 125 is secured to the pen top 105 m operation and ananged to rotate therewith The cam banel 125 includes a cam 126 m the form of a slot within the walls 181 of the cam banel Cam followers 127 and 128 projecting from slider blocks 123 and 124 fit withm the cam slot 126 On rotation of the cam barrel 125, the slider blocks 123 or 124 move relative to each other to project either the pen mb 119 or stylus mb 121 out through the hole 122 m the metal end piece 114 The pen 101 has three states of operation By turning the top 105 through 90° steps, the three states are Stylus 120 mb 121 out, • Ink cartndge 118 mb 119 out, and • Neither ink cartndge 118 mb 119 out nor stylus 120 mb 121 out A second flex PCB 129, is mounted on an electronics chassis 130 which sits withm the housmg 102 The second flex PCB 129 mounts an mfrared LED 131 for providing infrared radiation for projection onto the surface An image sensor 132 is provided mounted on the second flex PCB 129 for receivmg reflected radiation from the surface The second flex PCB 129 also mounts a radio frequency chip 133, which mcludes an RF fransmitter and RF receiver, and a controller chip 134 for controlling operation of the pen 101 An optics block 135 (formed from moulded clear plastics) sits withm the cover 107 and projects an mfrared beam onto the surface and receives images onto the image sensor 132 Power supply wires 136 connect the components on the second flex PCB 129 to battery contacts 137 which are mounted withm the cam barrel 125 A terminal 138 connects to the battery contacts 137 and the cam banel 125 A three volt rechargeable battery 139 sits withm the cam banel 125 m contact with the battery contacts An induction charging coil 140 is mounted about the second flex PCB 129 to enable recharging of the battery 139 via induction The second flex PCB 129 also mounts an mfrared LED 143 and mfrared photodiode 144 for detecting displacement m the cam banel 125 when either the stylus 120 or the ink cartndge 118 is used for writing, m order to enable a determination of the force bemg applied to the surface by the pen mb 119 or stylus b 121 The IR photodiode 144 detects light from the IR LED 143 via reflectors (not shown) mounted on the slider blocks 123 and 124 Rubber gnp pads 141 and 142 are provided towards the end 108 of the housmg 102 to assist gnpping the pen 101, and top 105 also mcludes a clip 142 for clipping the pen 101 to a pocket 6.2 PEN CONTROLLER The pen 101 is ananged to determine the position of its mb (stylus mb 121 or mk cartndge mb 119) by - 36 - lmagmg, m the infrared spectrum, an area of the surface m the vicinity of the mb It records the location data from the nearest location tag, and is ananged to calculate the distance of the mb 121 or 119 from the location tab utilising optics 135 and controller chip 134 The controller chip 134 calculates the onentation of the pen and the nib-to-tag distance from the perspective distortion observed on the imaged tag Utilising the RF chip 133 and antenna 112 the pen 101 can transmit the digital ink data (which is encrypted for secunfy and packaged for efficient transmission) to the computing system When the pen is m range of a receiver, the digital ink data is transmitted as it is formed When the pen 101 moves out of range, digital ink data is buffered withm the pen 101 (the pen 101 circuitry mcludes a buffer arranged to store digital ink data for approximately 12 mmutes of the pen motion on the surface) and can be transmitted later The controller chip 134 is mounted on the second flex PCB 129 m the pen 101 Figure 10 is a block diagram illustrating m more detail the architecture of the controller chip 134 Figure 10 also shows representations of the RF chip 133, the image sensor 132, the tn-color status LED 116, the IR illumination LED 131, the IR force sensor LED 143, and the force sensor photodiode 144 The pen controller chip 134 mcludes a controlling processor 145 Bus 146 enables the exchange of data between components of the controller chip 134 Flash memory 147 and a 512 KB DRAM 148 are also mcluded An analog-to-digital converter 149 is ananged to convert the analog signal from the force sensor photodiode 144 to a digital signal An image sensor mterface 152 interfaces with the image sensor 132 A transceiver controller 153 and base band cncuit 154 are also mcluded to mterface with the RF chip 133 which mcludes an RF cncuit 155 and RF resonators and mductors 156 connected to the antenna 112 The controlling processor 145 captures and decodes location data from tags from the surface via the image sensor 132, momtors the force sensor photodiode 144, controls the LEDs 116, 131 and 143, and handles short-range radio commumcation via the radio transceiver 153 It is a medium-performance (~40MHz) general-piupose RISC processor The processor 145, digital fransceiver components (fransceiver controller 153 and baseband cncuit 154), image sensor interface 152, flash memory 147 and 512KB DRAM 148 are integrated m a smgle controller ASIC Analog RF components (RF cncuit 155 and RF resonators and mductors 156) are provided m the separate RF chip The image sensor is a 215x215 pixel CCD (such a sensor is produced by Matsushita Electromc Coφoration, and is descnbed m a paper by Itakura, K T Nobusada, N Okusenya, R Nagayoshi, and M Ozaki, "A 1mm 50k-Pιxel IT CCD Image Sensor for Miniature Camera System", IEEE Transactions on Electromc Devices, Volt 47, number 1, January 2000, which is incoφorated herem by reference) with an IR filter The controller ASIC 134 enters a quiescent state after a penod of inactivity when the pen 101 is not in contact with a surface It incoφorates a dedicated circuit 150 which momtors the force sensor photodiode 144 and wakes up the controller 134 via the power manager 151 on a pen-down event The radio fransceiver commumcates m the unlicensed 900MHz band normally used by cordless telephones, or alternatively m the unlicensed 2 4GHz lndustnal, scientific and medical (ISM) band, and uses frequency hoppmg and collision detection to provide interference-free commumcation In an alternative embodiment, the pen incoφorates an Infrared Data Association (IrDA) mterface for short- range commumcation with a base station or netpage pnnter In a further embodiment, the pen 101 mcludes a pan of orthogonal accelerometers mounted m the normal plane of the pen 101 axis The accelerometers 190 are shown m Figures 9 and 10 m ghost outline The provision of the accelerometers enables this embodiment of the pen 101 to sense motion without - 37 - reference to surface location tags, allowing the location tags to be sampled at a lower rate Each location tag ID can then identify an object of mterest rather than a position on the surface For example, if the object is a user mterface mput element (e g a command button), then the tag ID of each location tag withm the area of the mput element can dnectly identify the mput element The acceleration measured by the accelerometers m each of the x and y dnections is integrated with respect to time to produce an instantaneous velocity and position Smce the starting position of the sfroke is not known, only relative positions withm a stroke are calculated Although position integration accumulates enors m the sensed acceleration, accelerometers typically have high resolution, and the time duration of a stroke, over which enors accumulate, is short 7. NETPAGE PRINTER DESCRIPTION 7.1 PRINTER MECHANICS The vertically-mounted netpage wallpnnter 601 is shown fully assembled in Figure 11 It pnnts netpages on Letter/A4 sized media using duplexed S'Λ" Memjet™ pnnt engmes 602 and 603, as shown m Figures 12 and 12a It uses a straight paper path with the paper 604 passmg through the duplexed pnnt engmes 602 and 603 which pnnt both sides of a sheet simultaneously, in full color and with full bleed An mtegral binding assembly 605 applies a stnp of glue along one edge of each pnnted sheet, allowing it to adhere to the previous sheet when pressed against it This creates a final bound document 618 which can range m thickness from one sheet to several hundred sheets The replaceable ink cartndge 627, shown in Figure 13 coupled with the duplexed pπnt engmes, has bladders or chambers for stoπng fixative, adhesive, and cyan, magenta, yellow, black and mfrared inks The cartndge also contams a micro an filter m a base molding The micro an filter interfaces with an an pump 638 mside the pnnter via a hose 639 This provides filtered an to the pnntheads to prevent ingress of micro particles mto the Memjet™ printheads 350 which might otherwise clog the pnnthead nozzles By incoφorating the an filter withm the cartndge, the operational life of the filter is effectively linked to the life of the cartndge The ink cartndge is a fully recyclable product with a capacity for prmtmg and gluing 3000 pages (1500 sheets) Referring to Figure 12, the motorized media pick-up roller assembly 626 pushes the top sheet directly from the media tray past a paper sensor on the first prmt engme 602 mto the duplexed Memjet™ pnnthead assembly The two Memjet™ pnnt engmes 602 and 603 are mounted m an opposing m-lme sequential configuration along the straight paper path The paper 604 is drawn mto the first pπnt engine 602 by mtegral, powered pick-up rollers 626 The position and size of the paper 604 is sensed and full bleed prmtmg commences Fixative is pnnted simultaneously to aid drying m the shortest possible time The paper exits the first Memjet™ pnnt engme 602 through a set of powered exit spike wheels (aligned along the straight paper path), which act against a rubberized roller These spike wheels contact the 'wet' pnnted surface and continue to feed the sheet 604 mto the second Memjet™ pnnt engme 603 Referring to Figures 12 and 12a, the paper 604 passes from the duplexed pnnt engmes 602 and 603 mto the bmder assembly 605 The pnnted page passes between a powered spike wheel axle 670 with a fibrous support roller and another movable axle with spike wheels and a momentary action glue wheel The movable axle/glue assembly 673 is mounted to a metal support bracket and it is transported forward to mterface with the powered axle 670 via gears by action of a camshaft A separate motor powers this camshaft The glue wheel assembly 673 consists of a partially hollow axle 679 with a rotating couplmg for the glue supply hose 641 from the ink cartndge 627 This axle 679 connects to a glue wheel, which absorbs adhesive by capillary action through radial holes A molded housmg 682 sunounds the glue wheel, with an opening at the front Pivoting side - 38 - moldmgs and sprung outer doors are attached to the metal bracket and lunge out sideways when the rest of the assembly 673 is thrust forward This action exposes the glue wheel through the front of the molded housmg 682 Tension springs close the assembly and effectively cap the glue wheel during peπods of inactivity As the sheet 604 passes mto the glue wheel assembly 673, adhesive is applied to one vertical edge on the front side (apart from the first sheet of a document) as it is transported down mto the binding assembly 605 7.2 PRINTER CONTROLLER ARCHITECTURE The netpage pnnter controller consists of a controlling processor 750, a factory-installed or field-installed network mterface module 625, a radio transceiver (fransceiver controller 753, baseband cncmt 754, RF cncmt 755, and RF resonators and mductors 756), dual raster image processor (RIP) DSPs 757, duplexed pnnt engine confrollers 760a and 760b, flash memory 658, and 64MB of DRAM 657, as illustrated in Figure 14 The controlling processor handles commumcation with the network 19 and with local wireless netpage pens 101, senses the help button 617, controls the user mterface LEDs 613-616, and feeds and synchronizes the RIP DSPs 757 and pπnt engme confrollers 760 It consists of a medium-performance general-pinpose microprocessor The controlling processor 750 commumcates with the pnnt engme confrollers 760 via a high-speed seπal bus 659 The RIP DSPs rastenze and compress page descnptions to the netpage pnnter' s compressed page format Each pπnt engme controller expands, dithers and pnnts page images to its associated Memjet™ pnnthead 350 m real tune (I e at over 30 pages per minute) The duplexed pnnt engme confrollers pπnt both sides of a sheet simultaneously The master pnnt engme controller 760a controls the paper transport and momtors ink usage m conjunction with the master QA chip 665 and the ink cartndge QA chip 761 The pnnter controller's flash memory 658 holds the software for both the processor 750 and the DSPs 757, as well as configuration data This is copied to mam memory 657 at boot time The processor 750, DSPs 757, and digital transceiver components (transceiver controller 753 and baseband cncmt 754) are integrated m a smgle controller ASIC 656 Analog RF components (RF cncmt 755 and RF resonators and mductors 756) are provided in a separate RF chip 762 The network interface module 625 is separate, smce netpage pnnters allow the network connection to be factory-selected or field-selected Flash memory 658 and the 2x256Mbit (64MB) DRAM 657 is also off-chip The pπnt engme confrollers 760 are provided m separate ASICs A vanety of network mterface modules 625 are provided, each providmg a netpage network mterface 751 and optionally a local computer or network mterface 752 Netpage network Internet interfaces mclude POTS modems, Hybnd Fiber-Coax (HFC) cable modems, ISDN modems, DSL modems, satellite transceivers, cunent and next- generation cellular telephone transceivers, and wireless local loop (WLL) transceivers Local interfaces mclude IEEE 1284 (parallel port), lOBase-T and 100Base-T Ethernet, USB and USB 2 0, IEEE 1394 (Fnew e), and vanous emerging home networking interfaces If an Internet connection is available on the local network, then the local network mterface can be used as the netpage network mterface The radio transceiver 753 commumcates m the unlicensed 900MHz band normally used by cordless telephones, or alternatively m the unlicensed 2 4GHz mdustnal, scientific and medical (ISM) band, and uses frequency hoppmg and collision detection to provide interference-free commumcation The pnnter controller optionally mcoφorates an Infrared Data Association (IrDA) mterface for receiving data "squirted" from devices such as netpage cameras In an alternative embodiment, the pnnter uses the IrDA mterface for short-range commumcation with suitably configured netpage pens 7.2.1 RASTERIZATION AND PRINTING Once the mam processor 750 has received and venfied the document's page layouts and page objects, it runs the appropnate RIP software on the DSPs 757 - 39 - The DSPs 757 rastenze each page descnption and compress the rastenzed page image The mam processor stores each compressed page image m memory The simplest way to load-balance multiple DSPs is to let each DSP rastenze a separate page The DSPs can always be kept busy smce an arbifrary number of rastenzed pages can, m general, be stored m memory This sfrategy only leads to potentially poor DSP utilization when rastenzmg short documents Watermark regions m the page descnption are rastenzed to a contone-resolution bi-level bitmap which is losslessly compressed to negligible size and which forms part of the compressed page image The infrared (IR) layer of the pnnted page contams coded netpage tags at a density of about six per mch Each tag encodes the page ID, tag ID, and confrol bits, and the data content of each tag is generated duπng rasterization and stored m the compressed page image The mam processor 750 passes back-to-back page images to the duplexed pπnt engine confrollers 760 Each pπnt engme controller 760 stores the compressed page image m its local memory, and starts the page expansion and prmtmg pipeline Page expansion and printing is pipelined because it is unpractical to store an entire 114MB bi-level CMYK+IR page image m memory 7.2.2 PRINT ENGINE CONTROLLER The page expansion and pπnting pipeline of the pπnt engme controller 760 consists of a high speed IEEE 1394 seπal mterface 659, a standard JPEG decoder 763, a standard Group 4 Fax decoder 764, a custom halftoner/compositor unit 765, a custom tag encoder 766, a lme loader/formatter unit 767, and a custom mterface 768 to the Memjet™ prmthead 350 The pπnt engme controller 360 operates m a double buffered manner While one page is loaded mto DRAM 769 via the high speed seπal mterface 659, the previously loaded page is read from DRAM 769 and passed through the pnnt engine controller pipeline Once the page has finished prmtmg, the page just loaded is pnnted while another page is loaded The first stage of the pipeline expands (at 763) the JPEG-compressed contone CMYK layer, expands (at 764) the Group 4 Fax-compressed bi-level black layer, and renders (at 766) the bi-level netpage tag layer according to the tag format defined m section 1 2, all m parallel The second stage dithers (at 765) the contone CMYK layer and composites (at 765) the bi-level black layer over the resulting bi-level CMYK layer The resultant bi-level CMYK+IR dot data is buffered and formatted (at 767) for prmtmg on the Memjet™ pnnthead 350 via a set of lme buffers Most of these lme buffers are stored m the off-chip DRAM The final stage pnnts the six channels of bi-level dot data (mcludmg fixative) to the Memjet™ pnnthead 350 via the pnnthead mterface 768 When several pnnt engme confrollers 760 are used m unison, such as m a duplexed configuration, they are synchronized via a shared lme sync signal 770 Only one pnnt engme 760, selected via the external master/slave pm 771, generates the lme sync signal 770 onto the shared lme The pnnt engme controller 760 contams a low-speed processor 772 for synchronizing the page expansion and rendering pipeline, configuring the pnnthead 350 via a low-speed senal bus 773, and controlling the stepper motors 675, 676 In the 854" versions of the netpage pnnter, the two pnnt engmes each pnnts 30 Letter pages per minute along the long dimension of the page ( 11 "), givmg a lme rate of 8 8 kHz at 1600 dpi In the 12" versions of the netpage pnnter, the two pπnt engmes each pnnts 45 Letter pages per minute along the short dimension of the page (8V2"), giving a lme rate of 10 2 kHz These lme rates are well withm the operating frequency of the Memjet™ pnnthead, which in the cunent design exceeds 30 kHz - 40 - CONCLUSION The present invention has been described with reference to a prefened embodiment and number of specific altemative embodiments. However, it will be appreciated by those skilled in the relevant fields that a number of other embodiments, differing from those specifically described, will also fall within the spirit and scope of the present invention. Accordingly, it will be understood that the invention is not intended to be limited to the specific embodiments described in the present specification, including documents incoφorated by cross-reference as appropriate. The scope of the invention is only limited by the attached claims.

Claims: - 41 - CLAIMS 1 In a network connected to an mteractive device and a registration server, a protocol for registenng the mteractive device with the regisfration server, mcludmg the steps of mstallmg a secret key and a public umque identifier m non-volatile memory m the mteractive device and m a database of the registration server, before the mteractive device is connected to the network, then, when the mteractive device is connected to the network, authenticating the mteractive device at the server by venfying the mteractive device's encryption, usmg the secret key, of a challenge message, and finally, if the authentication succeeds, registenng the mteractive device m the database of the registration server 2 The protocol accordmg to claim 1 , where the authenticating step mcludes the sub-steps of transmitting, from the mteractive device to the server, a registration request mcludmg the mteractive device's umque public identifier, generating, at the server, the challenge message, transmitting, from the server to the mteractive device, the challenge, encrypting, at the mteractive device and usmg the secret key, the challenge, transmitting, from the mteractive device to the server, the encrypted challenge, decrypting, at the server and usmg the secret key, the encrypted challenge, and authenticating, at the server and by comparing the decrypted challenge with the challenge, the mteractive device 3 The protocol according to claim 1 , including the further steps of generating, at the server, a session key, encrypting, at the server, the session key usmg the secret key, transmitting, from the server to the mteractive device, the encrypted session key, and storing, at the mteractive device, the session key for future use 4 The protocol according to claim 1, where the mteractive device is connected to the network via a base station connected to the network The protocol according to claim 4, where the base station mcludes a pnnter 6 The protocol according to claim 4 or 5, where the authenticating step mcludes the sub-steps of transmitting, from the mteractive device to the base station, a regisfration request mcludmg the mteractive device's umque public identifier, generating, at the base station, the challenge message, transmitting, from the base station to the mteractive device, the challenge, encrypting, at the mteractive device and usmg the secret key, the challenge, transmitting, from the mteractive device to the base station, the encrypted challenge, transmitting, from the base station to the server, the mteractive device's public umque identifier together with the challenge and the encrypted challenge, decrypting, at the server and usmg the secret key, the encrypted challenge, and - 42 - authenticating, at the server and by comparing the decrypted challenge with the challenge, the mteractive device 7 The protocol according to claim 4 or 5, mcludmg the further steps of generating, at the server, a session key, encrypting, at the server, the session key usmg the secret key, transmitting, from the server to the base station, the session key and the encrypted session key, storing, at the base station, the session key, transmitting, from the base station to the mteractive device, the encrypted session key, and storing, at the mteractive device, the session key for future use 8 The protocol according to claim 7, where the base station stores, m non-volatile memory, at least one session key associated with an mteractive device, the session key being retnevable via a public umque identifier of the interactive device 9 The protocol according to claim 7, where the mteractive device stores, m non-volatile memory, at least one session key associated with a base station, the session key bemg retπevable via a public umque identifier of the base station 10 The protocol according to claim 4 or 5, where the mteractive device commumcates with the base station via a wireless connection 11 The protocol according to claim 10, where the mteractive device connects to the base station when it comes withm wireless commumcations range of the base station 1 The protocol accordmg to claim 5, where the pπnter pnnts a first document m response to an mput received from the interactive device 13 The protocol according to claim 12, where the mteractive device generates the mput by sensmg coded data mcluded m a second document 14 The protocol according to claun 13, where the pnnter pnnts the second document, mcludmg the coded data

Inventors: LAPSTUN PAUL, LAPSTUN, PAUL
Applicants: LAPSTUN PAUL, SILVERBROOK KIA, SILVERBROOK RES PTY LTD, LAPSTUN, PAUL, SILVERBROOK RESEARCH PTY LTD, SILVERBROOK, KIA
Application year: 2000
Main classification: H04L9
IPC codes: B41J2, B41J3, B41J11, B41J13, B41J29, B42C1, B42C9, B42C19, B65H29, B65H37, G06F3, G06K9, G06K17, H04L9, H04N1, H04N7, H04Q7