Web Browsing

Effective Web Browsing Through Content Delivery Adaptation

Currently, the World Wide Web is being used extensively as an important medium for information dissemination. Its high cost effectiveness is prompting more and more companies to go online and engage in such types of e-business as Internet shopping, auctions, advertisements, and E-trade. Web designers must take several conditions into consideration to effectively provide Web content to users. First, although Internet bandwidth is becoming increasingly broader, content transmission speed from Web servers and end users is becoming increasingly diverse. This is because a variety of connection methods have become available such as dial-up, ADSL, and wireless. According to the report of the Ministry of Public Management, Home Affairs, Posts and Telecommunications in Japan, over 70% of home users are using narrow-band dial-up connections as of 2002. Therefore, not all users equally experience smooth Web access, and users often have to wait an inordinately long time to download a Web page which can cause frustration. Such a long download time is referred to as the World Wide Wait, and estimates in a recently published report indicate that the e-business market has lost 21 billion dollars per year due to impatient users who have terminated their Web transfers. This situation will not disappear even if broadband wireless access becomes widely available because the diversity of network access methods will remain, and Web pages will get “fatter” (i.e., more high quality and high-resolution images will be included) as network bandwidths broaden.

Second, as the WWW becomes a popular tool for getting information, devices other than personal computers, such as PDAs and cellular phones, are emerging that can access the Web. These devices have different characteristics with regard to display size, color depth, and acceptable content description languages.

Third, users have different preferences with regard to content delivery. For example, one user may want to download a Web page within 10 seconds, while another user may tolerate longer download times to get high-quality images. These situations make it difficult for Web designers to design appropriate Web pages for every user. Since it is costly to prepare and maintain a variety of Web pages to meet the diverse demands of each Internet user, most Web designers basically provide only a single set of Web pages—usually visually appealing Web pages with a large number of images, videos, and sounds to attract the attention of users. This is especially true for e-business sites that maintain a large number of Web pages. To cope with these conflicting conditions, many efforts have been made in content adaptation [Fox and Brewer 1996; Fox et al. 1998a, 1998b; Shimada et al. 1997; Han et al. 1998]. One representative effort is content trans coding that automatically converts content description languages (e.g., from HTML to WML) and image formats (e.g., from JPEG to GIF) and then adjusts the quality of inline objects in a Web page according to a given client’s network bandwidth and/or device capability. By adjusting the quality of multimedia content according to a client’s network bandwidth, page download time can be reduced.

However, the existing content trans coding mechanisms lack flexibility. For example, no mechanism exists that allows the content author to explicitly specify an upper limit for the transmission time, the most crucial parameter in overcoming the World Wide Wait. Moreover, most of these ACM Transactions on Internet Technology, approaches do not consider an important part of the nature of Web pages, that is, they use streaming just as video and audio streams do. The streaming nature of Web pages offers another possibility for reducing user-perceived latency. That is, transmitting inline objects in an appropriate order has the potential to reduce user-perceived latency and to improve the availability of Web pages.

In this article, we describe the design of an adaptive content delivery mechanism that enables a single set of Web pages to adapt to a wide range of network connections, from low-speed to high-speed ones. The adaptation in our mechanism is performed based on a set of policies that we call applicationlevel QoS policies or a-policies. We can explicitly specify these a-policies in terms of transmission time threshold, quality prioritization, format conversion conditions, and transmission order; which allows us to keep the quality of a Web page as high as possible. Thus, our contributions in this article are to define a standard language to specify various kinds of policies and to provide a framework to guarantee the transmission of adapted Web pages based on these policies. Our framework enables a single set of Web pages to adapt to a wide range of networks which we believe will free content authors from the burden of preparing multiple versions of the same Web page.

In addition, we introduce two kinds of methods to specify a-policies, one by content authors, and the other by end users. Content authors might consider the effort to describe a-policies a heavy burden, especially at commercial sites in which a large number of Web pages have to be managed. Thus, we provide an authoring tool equipped with an a-policy editor and generator to automatically create a-policies based on created templates. These templates contain semantic information expressing how the author wants page(s) to appear for a client (for example, display product images before advertisement images). By applying the template to Web pages, the tool automatically generates a set of a-policies, providing content authors an efficient and generic way to specify apolicies. On the other hand, appropriate a-policies should depend not only on content authors, but also on the Web page viewer as well which motivates us to develop another specification method. With this method, we try to reflect a user’s preferences for the kinds of a-policies that should be created by introducing preference profiles where an adaptation policy from the user’s point of view can be described.

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