Developing a Municipal Multimedia Information System Michael Weber, Martin Gumhold Department for Distributed Systems, University of Ulm
[email protected],
[email protected] Abstract Multimedia information systems are getting commonplace as kiosk systems in public areas or as online information systems in the Internet. This paper describes the development of a municipal information system that can be used in both domains. In the public area an ATM based client/ server structure is used which provides gateways for Internet access. The system offers retrieval of authority information using intuitive and associative access modes. We discuss architectural models and tools which can be used as a system environment. For content representation HTML is extended in order to reflect the designers' impression of such a system.
1
Introduction
Ulm and its surrounding regions are developing an information infrastructure for their inhabitants. An ATM-based backbone network shall allow private and commercial users to deploy new telecommunication and telecooperation services at a low participation cost. In order to enforce the development and acceptance of the entire undertaking a multimedia information service should help to enforce the inhabitant’s participation. This system should be accessible through public terminals placed at frequently visited locations. Using a public system can reach also people not having computers and network access at home. However, the content should also be accessible from the world wide web in a later phase. The content should target the citizens themselves and not tourists as most town information services do. Therefore information about town authorities has been selected as the initial content, which should be presented in a high quality screen design. Through this strategy citizens shall get acquainted to new technology and the usage of new media. Fears shall be decreased and a taste for using the information infrastructure more frequently shall be woken [8]. It is foreseen, that in future more citizens will participate in decision processes using the new technology leading to an open and transparent style of communal politics.
2
System Architecture
The network and hardware structure has been given to the development team a priori. The system is based on a client/server architecture. The twenty public terminals, the clients, are PCs equipped with 32 megabytes of main memory, a 2 gigabyte hard disk, a 17” touchscreen, and a sound board with speakers. The touchscreens are the only human interface to the system. These client terminals are connected through an ATM network to the server in the townhall. This server has the identical configuration as the client terminals except that the touchscreen is replaced by an ordinary screen and there are keyboard and mouse available. Clients and servers run Windows NT. The ATM network uses fiber enabling native 155 Mbit/s ATM connections. On top of ATM classical IP with TCP or UDP is used for communication. Despite having the clear roles of clients and server different architectural variants are possible: the online and the offline models. In the online model all data is stored at the server. The terminals
simply provide a viewer program which connects to the server to display the requested information (figure 1a). This could be accomplished by using a standard WWW-server, standard WWWbrowsers for the clients, and HTTP [2] as a transfer protocol. The online model has several advantages. Data consistency is preserved, since there is only one instance of each data item. Updating and adding data can be done at one central location. When more storage space for information is required, this can be added at the server by additional hard disks. The missing failure resilience is a major disadvantage of the online model. Network or server failures, or even server maintenance disable information access from the terminals. If there should be some kind of fault tolerance a client caching scheme would have to be implemented. Such caching schemes offer either weak consistency or they are difficult to implement [5]. Instead of the client-initiated dynamic caching based on the principle of locality, an active server-initiated replication mechanism could be used where information is partially replicated at the clients. The selection of which data to replicate and which not is a major problem with this solution. user interaction
Client
user interaction online access
Server
a)
Client
periodic update
Server
b)
Figure 1: Online and Offline Models In the offline model all data is fully replicated at all terminals. Moreover all system software components are also installed at each client. This lets clients act autonomously. However, information updates are only made at the server. Periodically the server mirrors new information (fi gure 1b). If the content is stored as files in a file system, FTP could be used as an update protocol, or a replication mechanism of a network file system. If the content is stored in a database then database replication mechanisms would have to be used [3]. Even when network partitions make a server connection impossible the clients remain fully functional. If leased lines are used, the duration of connections can be kept short and cheap. Maintaining data consistency is the major drawback of the offline model. During the disconnection interval clients are not updated and may thus be inconsistent with data at the server. If the amount of data exceeds the current client storage capacity all clients have to be extended by additional storage, which would be costly when many clients are connected to the server. 2.1 Evaluation and Design Decisions Each architectural variant has been evaluated according to (1) data distribution and data consistency, (2) access frequency and response times, (3) failure resilience, (4) communication complexity, and (5) content extendibility. Table 1 gives the results for the models. We decided to favour the offline model, since our clients are supplied with enough storage to fully replicate the data. Moreover it is possible to employ weak consistency via periodic updates, since changes of the information happen at a slow rate. Furthermore, the clients have read-only semantics, i.e. the primary data at the server is never updated by the clients. We use Windows NT’s file system to store the data and periodically use its replication service for updates. Currently this
is done iteratively to the clients during night. Per client the replication phase takes between 1 and 2 seconds per megabyte, during which the client cannot serve any user. Since only differences are propagated, the volume of transferred data is much less than 1 MB per update. Such short periods of non-availability are acceptable and save the effort of implementing sophisticated update mechanisms with constant client availability. Table 1: Evaluation of design criteria criterion online model data distribution
single image
full replication
data consistency
strict consistency, easy to maintain
weak consistency, easy to maintain, if updates occur at server only
user response time
slow with many users, always remote operation
fast, only local operation
failure resilience
3
offline model
single point of failure, vulnerable resilient to node and network failure by network partitions
communication complexity
high, all displayed data travels
low, periodical update of changed data
storage extendibility
at server only, cheap
in all clients, expensive
Software Development
Several candidate technologies can be used to implement the software of a multimedia information service which we evaluated according to several requirements. The user interface shall provide short response time and support exact positioning of visualized elements on the screen. Networking capabilities shall allow synchronization between server and clients. Access to a database shall enable information search. Full WWW interoperability for up- and download shall be provided. All content data shall be maintainable by city staff. From a program development perspective qualified developers should be available and a high market penetration of the environment should guarantee future maintenance. Authoring tools, such as Director or Toolbook [4], are well-suited for programming portable multimedia presentations. This aspect did not play a significant role in our considerations, since we faced a homogeneous system set-up. The database connectivity and networking capabilities of these tools are either not available or difficult to use. The performance of complex systems implemented with authoring tools did not fulfil our need for instant response times. Kiosk development environments are specific solutions to implement point-of-information systems. We evaluated Digital’s MIKADO [6] which uses a scheme-extension [11] as its programming language and MHEG [9] as a format for content representation. The functionality fulfilled most of our requirements. Even transaction systems, for e.g. electronic cash, could be integrated. However, MIKADO lacked access capabilities from the WWW to the internal data. Furthermore we did not have trained personnel who could immediately program in scheme. The third option was to use an HTML-browser. Since we could not fully express the desired information and button structures using standard HTML [10], we had to look for extendible browser software with a powerful programming environment. We discovered rich libraries for Borland Delphi, which included not only most of the desired browser code, but also plenty of
viewer software for all our envisaged media formats, data base access modules, and networking functions as freeware. For Delphi also a large number of well-trained students was available. Driven by the requirement list we decided to extend a standard HTML browser to our needs. One major issue has been that most information to represent is already page based. Since the city staff collects authority information using word processing software, converter programs can be used to feed this information also into our system. The update cycle is another argument: content is updated by far more often than the program code itself. Using authoring tools or kiosk development tools the program would need complete recompilation every time a single image changes. Last but not least, an HTML based system can easily be used from and in the Internet.
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Content Representation and User Interface
The HTML extension should support arbitrary graphical design as the screen designers required including free positioning of elements and the use of button effects. These extensions could be made by adding just one new tag and new attributes to HTML. The browser extension could also have been done by adding JAVA applets to the HTML pages. However, we did not pursue this, since maintenance or even creation of new applets by city staff seemed to be impossible. We introduced a tag for multiface buttons, buttons that change over time. Animated GIF could not be used, since the system should give visual and acoustical response to user actions. The example below shows a HTML section using the new tag .
-- images change every 4000 msecs
In order to support free positioning x-offset and y-offset attributes are added to the table cell tag
. The offsets are pixel values counted from the upper left corner of the screen. | some table cell content |
All new pages are registered at the data base. The HTML meta tag is used to specify an abstract and the keywords of a page. Keywords are used to perform associative searching. The abstract helps users to select from multiple search results.
The user interface is separated into two areas. The system area contains control buttons at fixed locations independent of which content page is being displayed. In the information area the actual content is shown. The two areas are visualized using different button types. Borders or different background colours as an additional coding are not necessary to generate the awareness of having two areas. Figure 2 shows a screendump of the user interface as seen at the system’s entrance page.
Colours are used moderately and only to wake interest for the information content. The only colour besides the different greys we use in the system is a pale green to display user input via the virtual keyboard. Important for touchscreen based systems are high contrasts and a light grey for the background. This reduces the reflection problems dark backgrounds have. On the other hand a grey is not as dirt and fingerprint sensitive as a pure white. Typeface Frutiger is used, a clear and without serifs font, which can be read even in small sizes and antialiased. All buttons are shown as 3-dimensional images. The system buttons are designed simple and colourless to lead the user’s view to the information area, which uses multiface buttons. The images on these buttons change periodically each having its own change frequency.
system buttons Figure 7: User Interface
5
information area with multiface buttons
Navigation and Information Retrieval
The information system is intended to be used by citizens of all ages. Because of their diverse backgrounds miscellaneous navigation routes are offered. The first way through the system is inspired by images and hopefully attractive themes. A user is animated to browse around because of the changing and colourful multiface buttons. As doing means learning this is a preparation for the time the person needs specific information. Another possibility is the intuitive approach. An individual looking, for instance, for information on how to get back the lost umbrella might navigate from „offices“ to the „lost and found office“. For the first two navigation modes the standard links of HTML are sufficient. The third navigation strategy is the associative approach. Normally the citizens don’t know the exact terminology that is used in offices. For instance, they just know they have a problem with the rent because money is short. The system should be able to aid the user to find the information pages of the social welfare office. An association database combined with an attribute-based search mechanism solves this navigation mode. It stores cues often used in conjunction with a certain theme as keywords. These keywords are coded in the HTML documents using the meta tag attribute „keywords“. As a first search result only a brief description of the found pages’ content is shown to the user in order to aid in the refinement of the search or in the final selection of a page. This description is part of every page using the meta tag attribute „abstract“. Instead of letting the user type in complete search words before the database is retrieved, every keypress limits the list of possible pages
the user can choose from. This method seems to be inferior to sophisticated methods for information space indexing like being applied e.g. in the harvest system [1]. However, since the authors of pages are members of the city staff, their knowledge of meaningful attributes and keywords easily extends the capabilities of an automatic system. A problem of search methods is dependability on correct spelling. Especially with the virtual keyboard it is difficult to type a longer word without spelling errors. In order to improve this behaviour a simple, yet powerful method is included which adapts the soundex algorithm [7] to the German language. The algorithm proceeds as follows. The first letter being entered is kept as this letter. All subsequent letters are coded according to table 2. Resulting sequences of identical numbers in the code are folded into one of the numbers. With this coding scheme the matching is performed between the entered word and the keywords in the data base. Table 2: Adapted soundex scheme HW 0 BFPV 1 CGJKQSßXZ 2 L
6
4
MN
5
R
DT
3
6 AEIOUYÄÖÜ 7
Conclusions
This paper described the development of a municipal information system. The development process from requirements to the operational system has been outlined. We sketched the different architectural choices and selected the offline model. The chosen development environment has been Delphi, since we decided to augment HTML for our purposes and needed a rich code library for this. The information structure has been designed to support intuitive and associative access patterns. For the associative search the soundex algorithm has been modified and applied to a keyword data base. The system architecture is open to integrate other viewers or even entire programs. The content can also be accessed through standard WWW-browsers but with restricted layout features. Acknowledgements. The authors appreciate the design work and fruitful discussions with Winfried Reinke and Günter Hörmann. Our thanks go to Ralf Engels, Marc Schnieder, and Jochen Zeitler for implementing the system, and to Robert Srocka for entering the initial content pages.
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References
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