A new transcoding technique for PDA browsers, based on content
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1. htrp fmordor atiga esf websi Ir a Dramata amppss sysberm bo SECER bard 38 Internist Explorer 15 57 m Intermet Expborer raj heti fmardar at umoa esiwebsi lfi Be remote aea gpstem t SBUGBE Board The remote communication cient alow users to perform al the beaks of the Compuber Arhitectura T conventional laboratory in a simple and irruit wey It 5 nc uewer an hitegrated prmirerment snos it contro or rrpiements al those tasks Fig 4 Navigator atomic page set En Internet Explorer 19 32 Eu Internet Explorer 15 40 fhei mordor at ao es webs Tr a i ea a i ph RR EE i D tremate appesa system bo SBLbBK Communication with the SE OBKE board 4 platfame ndependent virtual termina Edot The chert moke crecth tne users preferred editor Assemiolar Automati PY SSOLUC assembler called by pressing a bullion UUsdeacter amp buillir ende opbleader Is orovided which supports both LIE CRI and DOS CRALF3 5 Fig 5 Navigator atomic page set List with hyperlinks Fig 6 Representative icons NAVIGATOR ATOMIC PAGE GENERATOR Preprocessing Stage Conversion Stage OUTPUT VISIBILITY RULES HTML or XHTML DOCUMENT navigator page i VARIOUS DOM TREE CONVERSIONS Fig 7 Navigator atomic page generator DOM generates the tree hierarchy required in our philosophy and the new trees to obtain the navigator page set For non XHTML WWW contents we2. Images Given the PDA screen resolution and the reduced image size in pixels the occupied PDA screen area is estimated For any reduced element a readability threshold is applied If reduced element is smaller than its threshold it is considered unreadable and is labeled with 1 Otherwise it is labeled with 0 There are some exceptions for example HR lines are always unreadable Let n be the label of node n Then element labels are propagated across the XML tree as follows Fori 2 8 do For all nj do Let I4 be the set of all nodes n such that n nj 1 holds Then l n is the product of the labels of all nodes in In Finally all branches that do not contain a 0 label are pruned For the resulting subtree the following rules apply All nodes whose labels are 0 readable nodes are substituted in the naviga tion page by reduced representatives All nodes whose labels are 1 are replaced by an icon There is a different icon for each element tables lists text For a given element there are two possibilities with a different background color normal icon black and hyperlink icon blue if the original element is associated to a hyperlink Specific icons are resized so that their area is approximately equal to the screen area covered by all associated descendants Each icon is linked to an atomic page containing either the associated orig inal element or all original elemen
3. gt C ma OC ws DUC ne D g Qa cuum Fi Cet Cet Cet C orem 5 Editor Com munication Assembler Upkader CN i Client request for jdk 12 Client request for jdk 1 2 Client request iex le rmal users User s manual on lire Fig 9 Hierarchy tree of the page in figure 1 one accessed the WWW site from an iPAQ H3630 PDA The third one accessed the transcoded version from an iPAQ H3630 PDA They had to solve a quiz on laboratory usage We tracked two quality measures per group average success percentage of right answers and average access time time to finish the quiz In order to calculate access time we served all pages original and transcoded with Apache Apache traces follow the CLF standard Each line displays the IP address of the accessing computer GMT access date with seconds resolution submitted command GET POST and server answer OK 404 Individual user times can be easily extracted with a filter As we expected it was hard for group 2 to visualize normal pages on a PDA display This made users prone to commit more mistakes The first time the users in group 3 accessed the transcoded pages their access time was slightly longer than the access time in group 1 but success was similar and clearly better than success in group 2 In subsequent tests the performance of users in groups 1 and 3 was similar which suggests that users got used to the transcoding technique easily N
4. need a JTidy preprocessing stage to generate the appropriate input for the conversion stage Note that this conversion does not impose constraints on original WWW contents this is not the case of WML and c HTML A final remark HANd implementation is based on language conversion in a broad sense It can be considered a particular case of transcoding strategy 7 3 4 Transformation rules and representatives The following rules associate original page elements to their representatives in the navigator page The tree of the original page is followed in increasing hierarchical order ending at the root node ns Let nj n _1 denote a parent child node relationship between levels 2 and t 1 4 2 5 For a XML page that has not been explicitly created for a small display device it is assumed that a generic large display produces a good presentation Using a 17 1024x768 screen as a reference for a specific PDA the PDA to PC screen area ratio R 1 is calculated This ratio is used to reduce the size of all elements in the original XML page In case of local processing the user could set R manually Then the PDA screen area occupied by leaf nodes without descendants is calculated For the sake of clarity we comment the most typical cases although it is easy to find similar rules for other elements Text Since we are interested in readability the font size for the PDA screen after reduction is calculated
5. obtain its DOM tree 17 using DOM parser A DOM tree is a representation of a XHTML document as a tree of nodes each one corresponding to a element in the XHTML document Conversion stage This stage applies visibility rules to the DOM tree and obtains the navigator atomic page set from the resulting new DOM trees e OF 5 Ga 3 E 8 3 LX Remote access system to SBC68K board Client request for jdk lt 1 2 under development Client request for jdk 1 2 under development Client request external users User s manual on line Introduction The remote communication client allows users to perform all the tasks of the Computer Architecture II conventional laboratory in a simple and intuitive way It is however an integrated environment since it controls or implements all those tasks e Communication with the SBC68K board A platform independent virtual terminal e Editor The client invokes directly the user s preferred editor e Assembler Automatic MC68000 assembler called by pressing a button e Uploader A built in code uploader is provided which supports both UNIX CR and DOS CR LF S Record files Fig 1 Original page it occupies a full 17 1024x768 screen Internet Explorer 15 36 http mondo ait po es webs tral Drema appesa sysberm bo SBLGBK bared Fig 2 Navigator atomic page set En Internet Explorer Ax E E Internet Explorer htt Imarciar att cna es webs J ir a
6. 2 use microbrowsers to access WAP supporting WWW sites WML is designed to optimize text delivery over limited bandwidth wireless networks It supports WMLScript which is similar to EcmaScript but imposes minimal system resource demands It is unlikely that WML will handle color audio and video in the near future Typical WAP sites present a series of options for visitor access Whilst clearly limited this operation mode is satisfactory for the delivery of news stock quotes sports results travel inquiries and similar applications However it cannot sup port the capabilities of most WWW sites A WML version of a WWW page is in a sense a clipped version for the WAP enabled cell phone world 2 4 i MODE In February 1999 the wireless branch of Nippon Telegraph amp Telephone NTT DoCoMo launched the i MODE network 13 By May 2000 the service had more than seven million subscribers in Japan and the demand was so great that NTT stopped advertising for a while in order to install extra service capacity i MODE terminals access WWW contents over the PDC wireless network using a proprietary DoCoMo protocol A typical i MODE terminal has a 95x65 pixel screen which is sharper than most current cell phone resolutions In order to display WWW contents on such a small screen i MODE employs subsets of HTML 2 0 3 2 and 4 0 These subsets are called c HTML 14 which stands for compatible HTML This language is the only requirement for p
7. A new transcoding technique for PDA browsers based on content hierarchy F J Gonzalez Castano L Anido Rif n E Costa Montenegro Departamento de Ingenier a Telem tica Universidad de Vigo ETSI Telecomunicaci n Campus 36200 Vigo Spain javier lanido kike jvales rasorey det uvigo es Abstract This paper presents a new transcoding technique for WWW navigation on small display devices Hierarchical Atomic Navigation Un like previous techniques Hierarchical Atomic Navigation keeps all origi nal information in a readable way without imposing the use of a specific browser To achieve this goal a navigator page is used to represent orig inal contents in a symbolic way A set of representative icons replaces unreadable elements These icons are linked to actual individual con tents as a set of atomic pages Hierarchical Atomic Navigation can be used on any PDA regardless of OS and browser choice since both nav igator and atomic pages use widely supported standard formats e g XML HTML 1 Introduction In the future many WWW services will be accessed from cell phones and wireless Personal Digital Assistants PDA 1 4 Although GPRS and 3G systems may provide enough mobile bandwidth there is an intrinsic problem to be solved mobile terminals are small and therefore have small displays Most WWW contents are not designed for them 5 6 Searching information through a page is a complex task users are prone to incorr
8. bjects This could be achieved by means of tools like Rhino 18 Further enhancements of the HANd philosophy For example design of rules to generate hierarchies of navigator pages or in other words a represen tative icon could be linked to a new navigator page in a lower hierarchical level References 10 11 12 13 14 15 16 1T 18 Market Risks Security The Downside of com Research briefs http www infoworld com articles hn xml1 99 07 19 990719hnrbcom xml PDAs at PC technology guide http www pctechguide com 25mob3 htm Personal mobile communicators http www pdastreet com Lewis T UbiNet the ubiquitous Internet will be wireless IEEE Computer 32 1999 pp 126 128 Gessler S and Kotulla A PDAs as mobile WWW browsers Proc of the 2nd Int WWW Conference Chicago USA October 1994 Jones M Mardesen G Mohd Nasir N Boone K and Buchanan G Improv ing Web interaction on small displays Proc of the 8th Int WWW Conference Toronto Canada May 1999 Hori M Kondoh G Ono K Hirose S and Singhai S Annotation based web content transcoding Proc of the 9th Int WWW Conference Amsterdam The Netherlands May 2000 Resource Description Framework RDF http www w3 org TR REC rdf syntax Microsoft Pocket Internet Explorer http www microsoft com mobile pocketpc features pie asp Handy Fit to Screen http www micr
9. d a page fragmentation system based on external annota tion files 7 A transcoding process uses annotations to decide which elements will be delivered to the client Annotation files follow the RDF data model 8 to specify the relative priority of page elements punctuation The system is basically composed of a page splitting module and a generator which creates the client page The system includes an authoring tool to create annotation files with page fragment priorities Although clipped versions of WWW pages are adequate for small displays there is information loss according to criteria that are ignored by the end user Also page fragments must be punctuated with their priority this process may be accelerated by means of advanced authoring tools 7 2 2 Handy Fit to Screen Microsoft Pocket Internet Explorer 9 implements the Handy Fit to Screen fea ture 10 which resizes WWW pages to fit into small displays Obviously many page elements are not properly displayed To cope with this drawback Pocket Internet Explorer includes a zoom menu option that displays text in several sizes Handy Fit supports typical commercial standards including HTML and XML 11 and keeps all information Although it is a particular feature of Microsoft Pocket Internet Explorer similar tools could be developed for other browsers Nevertheless it does not work properly on large text pages that use small fonts 2 3 WML WML WAP devices 1
10. ect selections and scroll up and down most of their time It has been reported 6 that users with small screens are 50 less effective than users with large screens A trivial and obviously undesirable solution is limiting mobile WWW services to specialized WAP like ones like stock quotes weather forecasts and sports scores This paper presents a new philosophy to improve WWW navigation on small displays Our system described in section 3 is based on the Hierarchical Atomic Navigation concept HANd some or all elements embedded in a WWW page are identified by means of a reduced page preview the navigator page which is generated automatically Section 2 discusses related work Section 4 evaluates usability Finally section 5 concludes Additional authors J Vales Alonso R Asorey Cacheda J Garc a Reinoso D Conde Lagoa J M Pousada Carballo and P 5 Rodr guez Hern ndez This research has been supported by European Commission FEDER grant 1FD97 1485 C02 02 TIC 2 Related work 2 1 Web clipping Web clipping is based on delivering a clipped version of the original WWW page to a small display device First a page fragmentation process is carried out Then a human or an automated process specifies an importance value for every page fragment Low importance fragments are ignored when display space is limited For example elements that do not carry significant information in relation with their size Hori et al designe
11. evertheless there was no improvement in group 2 neither in success nor in access time It should be understood the results cannot be generalized since the users were skilled students However we think that they demonstrate the potential of the approach for small to medium traditional pages 5 Conclusions and future research In this paper we have presented a new transcoding technique for small display devices Hierarchical Atomic Navigation HANd Like the alternative transcod ing techniques in section 2 it may need manual adjustment when processing visually complex pages like Amazon com or www elpais es Nevertheless it has the following advantages over them No information loss All original elements can be shown on demand as atomic pages The navigator page is a readable overview of the original page using a re duced space Actual contents are accessible via their representatives atomic navigation Atomic navigation can be adapted to any WWW document including pages created by accessing ASP or PHP pages There is no need for a mark up lan guage that introduces content constraints or a specialized WWW browser both navigator and atomic pages are supported by standard mark up lan guages Current work is oriented towards completing the following objectives Integration of script languages in the framework A language processor is required to generate a hierarchy of explicit o
12. ich elements are shown Also HANd can be used on any PDA regardless of OS and browser choice since both navigator and atomic pages use standard formats This is a major difference with Microsoft Handy Fit a technique that is implemented by specific browsers 3 2 HANd page examples Figures 2 to 5 show the navigator atomic page set after processing the page in figure 1 All figures are captures taken on an iPAQ H3630 PDA The width ratio between figures 2 to 5 and figure 1 on a real screen is approximately 20 The left screen in figures 2 to 5 shows some possible user selections on the navigator page The right screen shows the corresponding atomic pages the atom icon is used to return to the navigator page in an implementation without frames Figure 6 shows a selection of representative icons used in navigator pages On a real PDA screen the icons are blue if the corresponding atomic pages contain hyperlinks 3 3 HANd page generator prototype The previous section described a navigator atomic HANd page set These pages are created by a HANd page generator which is shown in figure 7 The generator receives documents written in any language and processes them in two stages Preprocessing stage Non XML documents HTML TEX are converted into XHTML which is a reformulation of HTML 4 01 in XML The conver sion is performed by JTidy 15 the Java version of HTML TIDY 16 Once a XHTML document is available we
13. orting a WWW site to the i MODE system Since c HTML relies on ordinary HTML coding and uses common HTML tags c HTML pages can also be displayed on PCs i MODE terminals can display GIF images and half width Kana characters but do not support Java or script languages Unquestionably i MODE is a successful experience in the Japanese market Its main advantage is the lack of punctuation processing since clipping is an implicit consequence of using c HTML Consequently an i MODE WWW site is just a clipped version of the original site All elements outside the subset are no longer included in the i MODE page and therefore no longer viewable by i MODE terminals Again we are facing the problem of information loss according in this case to fixed criteria over a proprietary network From this analysis it can be concluded that most approaches rely on some form of clipping which yields high readability but has information loss Microsoft Handy Fit avoids that disadvantage but it is not adequate for large text pages In the next section we present a new philosophy that keeps all original information in a readable way and does not impose a browser choice 3 HANd 3 1 Philosophy The HANd philosophy is based on the fragmentation of the original page into zones These zones are sets of multimedia elements included in the original page e g images text paragraphs headers hyperlinks Java applets forms etc The user may select an
14. osoft com mobile pocketpc features articles web asp XML at W3C site http www w3 org WAP http www wapforum com NTT DoCoMo http www nttdocomo com c HTML http www nttdocomo com source tag index html JTidy http lempinen net sami jtidy HTML TIDY http www w3 org People Raggett tidy DOM at WSC site http www w3 org DOM Rhino at Mozilla site http www mozilla org rhino
15. ts associated to the corresponding pruned branch for intermediate nodes Adjacency rule all adjacent icons associated to elements of the same type are represented by a single icon Elements such as HR or BR are transpar ent when applying this rule Also other information irrelevant elements like small pictures bullets etc are considered transparent Figure 8 shows the three stages of the algorithm for a simple tree example a labeling b label propagation and c pruning Figure 9 shows the hierarchy tree of the page in figure 1 Note that several elements are pruned and replaced by the corresponding representative icon The adjacency rule applies to the object group in the dotted box 4 Usability tests In order to test the effectiveness of the new transcoding technique we performed usability tests based on the WWW site that starts with the page in figure 1 The site contains a user manual that explains how to use the remote access system to a third year laboratory course Arquitectura de Ordenadores II We divided a group of students into three testing groups The first one ac cessed the WWW site from the desktops in the laboratory room The second 0 N A l 1 0 O 1 l l 0 Fox D Q OQ ct 5 A o X OO a labelin b label propagation c pruning E propag Fig 8 Basic transformation algorithm C Hea Cm emen D D Com 1 The remote 1 zu Com D Cm 20 1 Cen D Cmm C 20C D0C m 50 Cm
16. y zone but only one can be displayed at original scale at a given time The main page or navigator page is a reduced overview of the original page The navigator page is always displayed on a side frame or pop up window It facilitates access to different atomic readable elements i e pieces of the original page using links to auxiliary or atomic pages on a second side frame or pop up window according to user preferences and display capabilities There are different navigator page representations for a given element in the original WWW page A reduced version of the element if still readable representative icon if it is decided that the reduced element is unreadable A key issue is element dependence All original elements are ordered in a tree hierarchy and any element is considered unreadable if all its descendants are unreadable In the navigator page the representative icon of an ancestor hides all its descendants but if that icon is selected all descendants are shown on the atomic page Navigator page representatives are placed in the same relative positions the corresponding elements occupied on the original page The goal is to provide the user with an idea of the original appearance of the page in a reduced space Note that HANd can be considered a sort of visual clipping see section 2 However unlike web clipping techniques every single information item is kept and the end user is free to decide wh
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