Issue No. 03 - May/June (2004 vol. 8)
Elisa Bertino , Purdue University
Krithi Ramamritham , Indian Institute of Technology, Bombay
The Internet has become the mode of choice for disseminating fast-changing data such as traffic and weather information, stock prices, sports scores, and even health-monitoring information. As a result, we now have a vast number of sources from which to obtain the constantly increasing amount of information on the Web. Users are accessing and monitoring such data for online decision-making via a wide variety of devices with quite varied bandwidth connections.
This enormous growth and diversity in terms of access devices, bandwidth, information sources, and content has made the problem of managing dynamic data more interesting and more challenging. In order to provide information that is actually useful to users, we need a variety of tools and mechanisms for data dissemination. In addition to the traditional approach, in which users explicitly request information when needed, service providers have developed more proactive techniques in which information sources automatically initiate the dissemination. Such new methods — often combining pull- and push-based dissemination with caching and proxy infrastructures — have generated considerable research and commercial activity, but many issues remain.
A first challenge derives from the trend toward ubiquitous computing (accessing data anywhere, anytime, anyhow). This requires innovative dissemination techniques that can alert users with relevant information on a variety of devices and according to different contextual conditions. With people increasingly using mobile access devices, developers must create ever more novel solutions. Mobile users' appetites for information is expected to keep growing, and seamless provision of information to users on the move has resulted in the reexamination of traditional wired solutions. In the process, researchers must contend with a dual challenge: mobile devices' small form factors and wireless connections' vulnerability.
Adequate performance when delivering large amounts of fast changing information to large user communities is another challenge. Techniques such as intelligent caching in an overlay network of proxies show promise in engineering information-dissemination systems that address this requirement. Personalization mechanisms are also important as users demand that applications tailor information to the specific tasks or situations they're involved with.
Given the continued intense activity in this arena, we invited researchers and practitioners to submit articles to this issue of IEEE Internet Computing describing aspects of information-dissemination technologies and applications. From among the numerous submissions, we selected the following three articles as representative of ongoing research and development activities.
In "A Decentralized Information Dissemination Infrastructure," Ragab and Mori discuss their proposal for the Autonomous Community Information System. ACIS is designed to let users communicate and exchange information with others in their communities, where a community is formed by a group of potentially geographically distributed users with similar information needs. The decentralized architecture underlying ACIS, and the application-level multicast technique it employs, promises to facilitate efficient delivery of dynamic content to large numbers of users.
Recognizing the tremendous increase in mobile users' access to the Internet, we have included an article that describes an attempt to tailor the standard publish—subscribe data-dissemination approach to mobile environments. In "Disseminating Information to Mobile Clients Using Publish—Subscribe," Mühl and colleagues describe their work with the Rebeca middleware system, employing intelligent filtering mechanisms to save network bandwidth both inside the infrastructure and at mobile clients.
One essential function that various components in an information dissemination infrastructure provide — be they sources, proxies, or edge servers — is that of caching. Due to its ability to reduce access delays and conserve network resources, caching on the Web is ubiquitous. Yet this topic poses several outstanding problems — particularly in the context of continuous queries over dynamic data. As Katsaros and Manolopoulos demonstrate in "Web Caching in Broadcast Mobile Wireless Environments," intelligent cache management is vital even with large caches. Their SliCache self-tunable cache-replacement policy uses intelligent slicing of the cache space and novel methods for selecting which objects to purge. Test results suggest this proposed policy is especially well suited for mobile clients.
A careful reading of the theme's articles reveals that Internet data dissemination is still evolving. Many of the proposed solutions are extensions, variations, or combinations of existing solutions, including
• user profiling for dissemination,
• dissemination and notification services,
• publish—subscribe systems,
• information filtering and summarization,
• proxy-based system architectures,
• network support, and
• security and privacy.
Still, there are several outstanding issues in information dissemination, particularly related to security and privacy. Information accessed concerning medical treatment for a disease, for example, could disclose or give hints about a user's sensitive personal information. Privacy-preserving information-dissemination techniques are thus an important component in long-term solutions. Other open issues include personalizing and adapting information for delivery, particularly according to contextual and historical information.
Despite these and other challenges, researchers and developers have already come a long way — as evidenced by the many technologies deployed thus far. The articles in this issue show a small cross section of some of the more promising technological responses to a few of the remaining problems.
Elisa Bertino is the research director at the Center for Education and Research in Information Assurance and Security (CERIAS), and a professor in the Computer Science department at Purdue University. Her research interests include databases, security and privacy, and object-oriented systems. She received a doctoral degree in computer science from the University of Pisa. Bertino is an IEEE Fellow and an ACM Fellow and received the IEEE Computer Society Technical Achievement Award in 2002. Contact her at firstname.lastname@example.org.
Krithi Ramamritham is the Vijay and Sita Vashee Chair Professor in the department of computer science and engineering and head of the School of Information Technology at the Indian Institute of Technology, Bombay. He is currently using concepts and solutions from database systems and real-time systems to address problems in embedded systems, mobile computing, intelligent Internet, and the Web. Ramamritham received a PhD in computer science from the University of Utah. He is a Fellow of the IEEE and a Fellow of the ACM. Contact him at email@example.com.