INF RMATIQUE INFORMATIK

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1 INF RMATIQUE INFORMATIK Zeitschrift der schweizerischen Informatikorganisationen Revue des organisations suisses d informatique Nr./No. 5 Oktober/Octobre 2001 Ubiquitous Computing

2 Pervasive and Mobile Computing Middleware How to Support Pervasive Internet Portals Klaus Rindtorff, Martin Welsch Internet access is no longer primarily a domain of browsers based on desktop PCs. The number of non-pc mobile access devices is fast outgrowing that of traditional PC based access devices. How can existing content as well as new services be delivered to all kinds of mobile Internet devices? Keywords: Pervasive Internet Portal, Middleware, Pervasive devices, XHTML (Extensible Hypertext Markup Language), WAP (Wireless Application Protocol) Introduction Information and information access are important elements in the daily life of many people today. This is true not only for the so-called information workers or for people in the IT industry, but is rather a general phenomenon in many environments. Not only the amount and diversity of information types is rising, but also the number of required and available applications and ways to access the information. Integration of business applications and data causes and requires at the same time complex dependencies for data and business processes. Independent of that, due to the ever-ongoing progress in hardware and software development, cheap information appliances have become available that support the increasing mobility of users. Small portable personal assistants combine high speed, low power computers and wireless communication, data storage in persistent semiconductor memory and coin size disk drives, small colour displays, video and speech processing technology. This will give users the freedom not only to communicate efficiently at any place in the world but also to access local information as well as information residing in the Internet at any place and any time. In this context, the term Pervasive Computing was coined. It is often used synonymously with Ubiquitous Computing and relates to the next dimension of personal computing. It is not only about extending availability but may go as far as blending computing services into the fabric and background of our daily life. Using computing technology and accessing Internet facilities is no longer consciously perceived, but happens rather under the covers. Portals: The Next Wave of E-Business Since e-business has emerged, we have seen several waves of e-business applications. During the first wave, companies published information like company profiles, catalogues, etc. available via the Internet. To actually interact with a particular company, people still had to send a fax or give one of the company s employees a call. With the next wave, interaction with companies through the Internet became possible; companies started to allow people to order goods or request services via the Internet, banks deployed home banking applications or online brokerage applications which are accessible via the Internet. Now we see developments with new interactions like business-to-business and government-to-citizen. More and more companies establish connections to their buyers and suppliers through the Internet; governments and public institutions open up for access by citizens via the Internet, e.g. for submitting tax statements. On the other hand, users need to maintain an overview and are interested to focus on the relevant aspects only, out of the nearly unmanageable mass of available offerings and information. This has lead to the idea of portals, which present information and access to applications and services in a personalized way to their users. The user tailors the portals content and behaviour to his personal needs thus streamlining interaction, reducing navigation load and hiding unwanted or unnecessary information. A portal helps to find the services of interest faster and more conveniently. Klaus Rindtorff studied at the University of Dortmund where he received a Diploma in Computer Science. He joined IBM in 1989 in the Böblingen Development Laboratory where he worked on several software development projects. Since 1999 Klaus works as a software architect in the WebSphere Portal Server development of the IBM Pervasive Computing division. He is one of the authors of the book Pervasive Computing Technology and Architecture of Mobile Internet Applications published by Addison-Wesley. <rindtorf@de.ibm.com> Martin Welsch studied physics at the University of Marburg. In 1984, he joined IBM at the Böblingen Development Laboratory. He has worked in various hardware and software areas in projects ranging from processor micro code through large systems software to smart card development. He has been active in the pervasive computing field since its founding. He is author of various publications and holds several patents. In addition to his work at IBM, he is professor at the Faculty for Mathematics and Computer Science at the Friedrich-Schiller-University of Jena. <martin.welsch@de.ibm.com> INFORMATIK INFORMATIQUE 5/

3 Content 1 Content 2 Content 3 Content 4 Portal Fig. 1: A pervasive Internet portal connects various devices with content from various sources The Pervasive Internet Portal Combining the portal idea with the possibilities that Pervasive Computing can offer, results in new types of portals. These new portals do not only address the PC or network computer as an Internet access device. The portal function is now also available for users of devices with limited capabilities and very different user interfaces, like Personal Digital Assistants (PDAs), mobile phones, Internet screen phones or voice telephones. Rather than providing a separate portal for every type of device, for example a WAP portal for WAP phones only, it is desirable to support various types of devices with a single infrastructure and a common interface to the content. This is the objective of a pervasive Internet portal middleware or infrastructure, as presented here. The amount of transactions that are processed via the Internet and the value of information that is distributed via the Internet are ever increasing. Therefore, scalability and extendibility are indispensable design points for every portal; in particular, for a pervasive Internet portal aimed at supporting devices that soon will outnumber PCs. The pervasive Internet portal delivers content and applications from various sources to subscribers via various channels. The content to be delivered and its appearance are personalized to meet the preferences and needs of subscribers. The portal bundles various content or application channels, which appear in the portal as portlets. Portlets may be part of the portal itself or they may be provided by third parties. The most important aspect of mobility for a portal is not so much that the client is mobile, but that the client environment is changing. New modes of access and channels with new communication characteristics come into play. The following sections will now focus on those aspects. More information on Pervasive Computing issues in general can be found in [Burkhardt et al. 01] and [Hansmann et al. 01]. Infrastructure As long as personal devices like organizers and personal digital assistants were isolated from networks, the communication and data exchange with other computing devices was only possible through proprietary methods within a line of products or from the devices to a PC using special software. In the pervasive world millions of devices, subscriber identification modules, public land mobile networks (PLMN), public switched telephony networks (PSTN), gateways, e.g. from WAP and Voice to IP, servers, and applications are interconnected. Last but not least, system management and billing systems must be integrated. Content providers, shops, market places, financial services, and enterprises use this infrastructure to offer their services to their clients. Pervasive Internet portals provide gateways to adapt the pervasive devices to the standard Internet protocols. They also deliver a variety of functions like personalization, mobile device management, security, and data synchronization. Portals are also able to maintain stable application interfaces between applications and various different devices with rapidly changing features. Mobile Devices When accessing the World-Wide Web with a personal computer, HTML is the lingua franca for all browsers. However, because of the characteristics of mobile devices, dedicated markup languages have been introduced for them. The disadvantage of having so many markup formats is that all content available from the Internet has to be accessible in various specific formats suitable for rendering on a specific mobile device. Hopefully the availability of XHTML (extensible Hypertext Markup Language) will replace all of them with a single markup language again. There are currently three different types of browsers available for mobile devices: 1. HTML markup: Full support of the HTML standard is typically not feasible on relatively small devices like PDAs. Most browsers falling into this category limit the supported HTML tag set. Problems often exist with the support for images, frames, and scripting. Because Web sites usually are created with the capabilities of PC-based browsers in mind, the presentation of information content from these sites on PDAs is mostly unsatisfying. 2. Dedicated markup: Instead of HTML, these browsers support a different markup format optimized for small devices. This can be WML, compact HTML, or other device-specific formats. Sometimes the usual translation on the gateway is omitted and the plain textual markup is parsed on the device itself. Due to the relatively simple format, this is even feasible for devices with limited memory. The results are good but the number of available sites is still relatively small. 3. Markup conversion: Browsers in this category connect the user through a custom gateway server that can filter out unnecessary HTML coding and convert the markup and images into a device-specific format. These browsers usually achieve excellent results but use a proprietary markup. 18 INFORMATIK INFORMATIQUE 5/2001

4 Most client software is available free but works only with an appropriate gateway server. Device Adaptation In order to support multiple device types, a pervasive Internet portal has to identify the actual device being used when generating the appropriate data. First of all, this is necessary to provide the appropriate markup suitable for the specific device capabilities. However, it is not sufficient to just generate the appropriate format alone. Because of the high degree of specialization in mobile devices, it is also important to adapt to the available input technologies and usage patterns. For example, huge tables or selection menus that work for a PC browser have to replaced by other, more appropriate layouts and interaction methods for PDAs. This is especially important when using voice recognition technologies to interact with a user. Not only the whole dialogue flow may have to be changed to accommodate for the specific device characteristics. The whole interaction or usage pattern may change and even lead to completely new usage scenarios. Usually the device type detection is achieved by checking the user-agent string sent as a part of each HTTP request. While this differentiation is acceptable for most applications in use today, it has some significant shortcomings. Mobile phones supporting the WAP standard are already available with different screen sizes and in the future more devices with even more different capabilities will become available. The actual markup and the layout of content available from the Internet cannot be based on the user-agent information alone. Standards like the Composite Capability/Preference Profile (CC/PP, see [W3C 99]) will be required to assist in the device adaptation of information. Personal Digital Assistants A typical graphical Web browser for PDAs runs through a custom proxy server (gateway) to filter out unnecessary HTML coding and convert images. Pages are downloaded from the Internet to the device during synchronization. They are stored and can be accessed offline. If the device is connected to the Fig. 2: HTML page converted for the PDA Fig. 3: PDA version of the page from the same Web site network using a modem, online browsing is possible as well. Figure 2 demonstrates how an actual HTML page is displayed on a Palm PDA after conversion by the gateway. Figure 3 shows another version with improved navigation and dedicated markup for PDAs available from the same Web site. Smart Phones Mobile communication services provide limited data rates and lower reliability compared with switched line networks. Compared to modern desktop computers, mobile devices only provide a very constrained application environment tailored to small, low weight devices with low energy consumption powered by small, rechargeable batteries. Mobile users demand for devices which are easy to use and are adapted to the mobile environment. The standard PC methods to access and manage Internet applications cannot be directly mapped to the mobile environment because too many user interactions and lengthy data transfers would cause customer dissatisfaction. Therefore, mobile equipment manufacturers founded the Wireless Application Protocol Forum (WAP Forum, see [WAP 98]) in 1997 to define an architecture that extends the Internet technology for mobile devices. Founding members were Ericsson, Motorola, Nokia and Openwave Systems. Today the WAP Forum comprises over 200 members ranging from network operators over mobile device suppliers to content developers and many IT companies. Wireless Application Protocol The WAP architecture defines an optimized protocol stack for communication over wireless lines, an application environment for mobile phone applications, a content description language, and a miniature browser interface. The ability to work with a wide variety of devices is a key feature of the WAP architecture. The mobile user interfaces are typically limited: Small display: A standard mobile phone display has a size of 96 by 65 pixels. Likewise, a PDA display is slightly larger at 160 by 160 pixels, whereas today s desktop computer feature screen sizes of 1024 by 768 pixels and larger. INFORMATIK INFORMATIQUE 5/

5 Fig. 4: The Ericsson R380 mobile phone (Picture courtesy of Ericsson) Restricted input capability: Mobile phones offer a keyboard with twelve keys for data input, which makes entering text a time-consuming process. For example, entering the letter z requires four keystrokes. Dictionary assisted input methods like T9 or Octave help to make entering text more convenient. Limited memory and processing power: A typical mobile phone has 8 to 32 MB of RAM and a 16-bit digital signal processor running at about 10 to 20 MHz, while desktop computers come with 128 MB of RAM and 1 GHz processors. Low speed network connections with high latency: Today, a GSM channel, which is typically used for WAP in Europe, offers 9.6 kbps compared to 56 kbps of an analogue PC modem or even 768 kbps with ADSL. These limitations have influenced the WAP architecture at various levels. The replacement of HTML pages (typical several Kbytes) by highly condensed WML pages, called cards, reduces the overhead of content presentation and reflects the limited display capabilities of mobile devices. A compact binary encoding of the data stream minimizes the data flow between device and server. The protocol and the browser are designed to run on very small, embedded systems with sub-second response time. Within a rather short time, the WAP architecture has grown into a very complex specification with many overlaps with the global Internet architecture. Some of the basic assumptions like limited data rate and client processing power are not valid for the high end of mobile devices any more. Therefore, many solution providers, but also device and equipment manufacturers, favour a rapid merging of WAP and Internet technology into a mobile Internet architecture. However, WAP technology is pretty mature, is supported by major industry players and will exploit the improved speed of future GPRS and UMTS systems. Therefore, the WAP architecture and systems built on this foundation will certainly play a significant role in the pervasive computing industry and will be embraced by the global mobile Internet architecture. i-mode i-mode is an Internet service for mobile devices that is currently available in Japan and soon also in the USA and in Fig. 5: i-mode device Europe. It is well accepted with several millions of subscribers. It allows users to browse specially formatted Web sites and to receive using their mobile phones. Third generation i- mode phones are offering a display size of about 24 x 10 characters. i-mode uses a packet-switched communication service with 9.6 kbps that allows for permanent connections. The monthly fee depends not on the connection time but on the number of packets exchanged. An i-mode phone is tied to a service provider, changing a service provider requires purchasing a new phone. The i-mode gateway is always installed at the provider s site. Mails are stored at the server or in the phone depending on the business model of the service provider. The size of mails is limited to a certain size, 500 characters for example. Longer mails are truncated. Newer i-mode phones are supporting the SSL end-to-end security protocol without client certificates. Root certificates of the well-known trust centres are stored in the phones. The user can disable these certificates partially or completely. Most i- mode phones do not support cookies; this makes a special cookie proxy necessary for supporting complex Web applications. A Java Micro Edition VM is also integrated in some new phone models. Java applications must implement a specific base class defined by the virtual machine, because Java applets or AWT are not included in the class library. The functions of the VM are very limited, for example only a single application can be executed at a time and access to the phonebook is disabled due to security reasons. Outlook The so-called third generation of mobile devices offers increased bandwidth and more processing power than the second-generation devices. This brings standard Internet 20 INFORMATIK INFORMATIQUE 5/2001

6 technologies like the TCP/IP stack and a subset of HTML into the reach of mobile phones, which might limit the usage of WML and the WAP stack to low-end devices. Since the standard Internet protocols are designed for wire-line networks, there is a need to extend the functionality to wireless devices. The World Wide Web Consortium (W3C) develops technologies to merge wireless and wire-line technology to a single extendable basis. Composite Capability/Preference Profile (CC/PP) An ever-increasing number of different smart devices will appear in the future. Thus, the adaptation of content to display capabilities and data rate will be of utmost importance. User preferences, like language selection, have to be considered as well. The Composite Capability/Preference Profile (CC/PP) enables devices to provide capability profiles to gateways or servers for adapting content to the device and the user preferences (see [W3C 99]). A CC/PP profile contains the hardware and software configuration as well as the user settings. The profile is encoded in the XML/RDF format. RDF (Resource Description Framework) is a W3C standard to exchange metadata between applications in a machine-readable form (see [W3C 00 a]). The Extensible Hypertext Markup Language (XHTML) XHTML is the XML based successor of HTML 4.0. HTML and XHTML are recommendations for the Internet community defined by the World Wide Web Consortium (see [W3C 00 b]). It allows mobile phone manufacturers to design a language that fits their needs based on HTML, the standard publishing language of the World Wide Web. XHTML is a family of document type definitions (DTDs) providing a subset or an extension of HTML 4.0 depending on the device where it is used. XHTML requires documents to be well formed XML. The W3C has defined a special XHTML subset for pervasive devices named XHTML Basic. XHTML Basic is designed for appliances like mobile phones, television sets, PDAs, vending machines, pagers, car navigation systems, mobile game machines, digital book readers, and smart watches, but is still rich enough to be used for simple content authoring. New document types can be defined by extending XHTML Basic in such a way that XHTML Basic documents are in the set of valid documents of the new document type. Summary The necessity to maintain overview and reduce navigation load when accessing the Internet through standard PC browser technology has led to the concept of portals. Independent of that, general continuing advances in hardware and software development have led to the availability of affordable portable information appliances like PDAs and several different kinds of phones with Internet access. The combination of both aspects yields pervasive Internet portals. The most important types of access devices and their characteristics with respect to mark-up languages, device recognition and matching topics were discussed and a possible solution to the proliferation of independent different mark-up languages was described. References [Burkhardt et al. 01] J. Burkhardt, H. Henn, S. Hepper, K. Rindtorff, T. Schäck: Pervasive Computing - Technology and Architecture of Mobile Internet Applications; Addison-Wesley, 2001 [Hansmann et al. 01] U. Hansmann, L. Merk, M. S. Nicklous, T. Stober: Pervasive Computing Handbook; Springer, 2001 [WAP 98] WAP Forum; Wireless Markup Language; April 1998; [W3C 99] W3C; Composite Capability/Preference Profile (CC/PP); July 1999; [W3C 00 a] W3C; Resource Description Framework (RDF); March 2000; [W3C 00 b] W3C; The Extensible Hypertext Markup Language; January 2000; INFORMATIK INFORMATIQUE 5/