The Graphics Information Sharing Platform for Mobile Computing based on SVG

1. Introduction

For the past few years, we have witnessed the rapidly growing popularity of WWW connection services in the field of mobile computing. Especially the WWW connection services via cellular phones have been expanding in use all over the world from Japan to other countries in Asia, Europe and US. Around the initial stage, the main pillars of the WWW services were composed of such text-based content providing such services as electronic mail and online news. However, with the evolution in the hardware specifications of cellular phones, a variety of contents and media such as sound, raster images and Java applications have gradually superseded the test-based ones and distributed to the subscribers as the multi-media services. On the other hand, the vector graphics has recently received much attention as a general WWW media Traditionally the mainstream vector graphics have been PDF and FLASH formatted by Adobe Systems and Macromedia respectively, both of which have been used for such applications as online publishing, animation, CAD and map. However, these are essentially corporate-proprietary formats and therefore there has not exist any platform-neutral WWW-standard vector format to date. Against this background, the standardization process of the specifications of two-dimensional vector graphics format has recently been launched that led ultimately to the formatting of SVG (Scalable Vector Graphics). WG was established in 1999 and the SVG 1.0 specifications has been completed in September 2001 and published as Recommendation. Currently the standardization process of SVG Mobile, SVG 1.1, and SVG 2.0 has been in progress. In light of the above, it is highly expected that demands for SVG in addition to texts and raster images will get stronger from now on especially in the area of mobile WWW computing. This article was written to propose a new graphics information-sharing platform using SVG that mainly targets at the mobile computing. This platform(Web graphics browser) can overlay distributed multiple graphics contents from multiple WWW servers by using common coordinate system. This function enables interoperability between multiple information services, such as map information service, restaurant information service, weather information service, traffic information service, location information service, etc. Such service architecture does not exist on any other platform. Moreover,this platform proposes the following three points.

1. Global(common) coordinate system description specifications for interoperability of realworld information

2. SVG subset specifications for mobile computing

3. Encoding system of SVG data

2. Current status of the Japanese mobile phone services

The Japanese mobile phone market has been rapidly expanding to date as clearly shown in Fig 1.

As the overall picture of the current status, we need to pay attention to the rapid development of the WWW content services via cellular phones. At present, the following three major carriers, i.e., KDDI, NTTDoCoMo and J-Phone, are providing such WWW content services as Ezweb, i-mode by and J-Sky respectively. Around the start of the services, the services were limited to E-mail, news and gourmet information and online shopping, all of which are based on text and bitmap formats due mainly to the hardware limitations such as coarse LCD (monochrome, resolution with dozens of pixels per square), slow transmission speed (KDDI: 14.4Kbps, NTT DoCoMo 9.6Kbps, J-Phone:9.6Kbps). However, due to some improvements in the hardware specifications, much higher-grade services using multimedia contents such as voice and images in addition to text and bitmap images and Java applications has recently gained popularity among users. NTT DoComo has started the next generation mobile phone service from October 2001, followed by KDDI scheduled to launch in April 2002. In the coming mobile phone services such as IMT-2000, the transmission speed will be upgraded at 144Kbps-2Mbps allowing a high speed transmission of data. Also, various location information services will be expected to become indispensable for the users with LCD enhanced high screen resolution of 200-300 dpi mounted as the standard. Thus, it is projected that, in addition to the existing contents, contents with more interactive and powerful representation capabilities would prevail among users. We think that scalable vector graphics (SVG) is very likely to be the most potential leading candidate for these contents.

3. Outline of SVG

SVG is an open and two-dimensional vector graphics format oriented toward the WWW connection services and the standardization of WWW is currently underway by W3C (World Wide Web Consortium). For the traditional raster graphics formats, JPEG,GIF and PNG are formulated as WWW standard formats. However, in the area of vector data, PDF and FLASH has been used as the mainstream formats but not categorized as WWW standards. However, in response to the growing demands for WWW standardized vector data targeting at such applications as online publishing and CAD and map, the standardization of SVG 1.0 was completed in September 2001 and subsequently published as Recommendation. Also, we are now in the midst of working process for SVG 1.1, SVG 2.0 and SVG Mobile. Since almost all major vendors has participated in the process and worked together collaboratively to complete the standardizations, it is highly expected that these new formats will easily gain footholds in the market and eventually supersede the existing formats. We would like to take up some of major features of SVG as follows.

4. Mobile applications using SVG

As described above, we think that the LBS(Location Based Service) will be certain to become mission-critical in the next generation mobile phone service. As specific examples for these services, we can take up such various services as distributions of shared location information like the rendezvous service, shop information and human navigation etc. To put these services to practical use, we think it essential to have their map information based on the realworld information. Furthermore, we think that some features of SVG (such as vector graphics, openness, interactivity, flexibility and extensibility) are very suitable for the representation of the real space information represented by map information. However, some improvements must be rendered to the current SVG specifications to make optimum use of the SVG features as described below.

1. Due to the current SVG specifications being too large to use for the mobile environment, we need to have subsets of SVG targeted at mobile devices.

2. To share the real space information scattered around on multiple servers on the WWW, we need to create a framework by which the specification can be extended to arbitrarily define the coordinate system for contents and the information obtained through this process can be utilized to interoperate the real-space information.

3. As SVG data consists of plain text data, though it provides us with high extensibility, it also causes such problems as lowered efficiency for storing data, increased processing load at the receiving end. Therefore, it is necessary for us to find a solution to increase the data storing efficiency while lowering the processing load at the receiving end.

In this article, we would like to focus our discussions on the SVG Mobile specifications, the global coordinate system and SVG encoding methods to resolve these issues.

5. Sharing of realworld information through layering

Originally, the WWW can be said to be a framework for sharing distributed information independently stored on multiple servers working under the infrastructure of the Internet, and the key architecture of the WWW has been the hyperlink function. Around the start of the WWW, the distributed media was centered for text files like document publications and, then with the appearances of rater images such as GIF, JPEG and PNG, online catalogs has also been eventually included in them. Further, we are now witnessing the rapid prevailing of online publishing, animation, CAD and map, all of which use vector graphics format. Thus, even though we can now have a great choice for the media to be used, hyperlink is still only single architecture for sharing various information. Hyperlink has a merit of high usability for sharing text data, but not sufficient to share graphics data. This is the main reason why we are proposing for the creation of a new framework for graphics information sharing based on the WWW with a new architecture and the establishment of layering of distributed graphics as a new concept for it. In spite of the simplicity involved, this layering method is very effective as illustrated in Fig 3.

Due to the inability of layering capabilities, the WWW services based on the traditional graphics data formats have required the preparation of two sets of information, i.e., map information and gourmet information, to provide the user with gourmet information. However, if the layering could be utilized, we will be able to do the same thing with the preparation of only gourmet information by utilizing the layered map information available from another server. Thus it will make it possible for both large and small information providers to work together for the distribution of information. However, to realize this kind of architecture, we need to define the coordinate system for contents and have them layered within the same coordinate system to obtain a meaningful layering. (Naturally it does not make any sense simply to have graphics contents layered along the boundaries). In other words, we need to define the coordinate systems arbitrarily for contents to share the realworld information represented by map information independently distributed on multiple servers. As the current SVG does not have any method to define the common coordinate system for the sharing of graphics contents, we are using a global coordinate system as extension to the specifications to make up for the part, the concept of which is based on Namespaces in XML

6. The SVG Mobile specification

Since the existing SVG 1.0 is targeted at high-end devices such as desktop PCs, it has been pointed out that the specification is too large for the environment of mobile terminal devices and therefore a new specifications based on the subsets should be created that is specifically tailored for the mobile environment. Against this backdrop, the standardization process of SVG Mobile specifications has started within the SVG WG of the W3C that is now in the midst of the process. SVG Mobile specifications consists of two profiles, i.e., SVG Tiny profile and SVG Basic profile. SVG Tiny profile is targeted at the lowest-end devices with very limited hardware specs such as cellular phones currently marketed in Europe and US. On the other hand, SVG Basic profile is targeted at low-end devices with relatively constraint hardware specs such as Japanese cellular phones or PDAs represented by PalmOS. Though we are still discussing the detail of the specifications, when the standard specifications of SVG Mobile are formulated in the future, we will naturally make every our specification in compliance with the standard specifications. Also, we show below the example for extensions of "Global coordinate system" that can define the coordinate system arbitrarily for contents to share the real-space information represented by map information independently distributed on multiple servers. In the Fig. 4, <globalunit> is the part to define the name of common coordinate system and can be defined by any character strings.

7. SVG encoding

SVG composed of plain test data gives us a merit of high legibility and easier extensibility but at the same time, causes us to face such problems as relatively high data volume and insufficient security during the transmission of data over the network as well as a large load for purging processing at the receiving end. Especially in the mobile environment where by nature the network connection is likely to be erratic and the hardware resources are limited, these problems significantly affect the performance. To resolve these problems, we would like to propose in this paper XEUS (Xml document Encoding Universal Sheet) which is an universal encoding formula.

8. Summary

In this paper, we proposed the shared information platform using SVG targeted at the mobile computing represented by cellular phones. By presenting this new formula, we also proposed a new concept of "layering" using the information of the coordinate system to share graphics information and explained the necessity for interoperating graphics independently distributed on the WWW. Further, we proposed a new encoding formula called "XEUS" for distributed SVG data that can resolve XML associated shortcomings such as relatively large data volume and heavy applications processing load at the data-receiving end. Finally, we confirmed the effectiveness of our new formula "XEUS" by the evaluation test described above. With these encouraging results, we have now a plan for the implementation of this platform into mobile phone terminals to provide various SVG contents shared services for mobile phones.