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Motivated by limitations in today's host-centric IP network, recent studies have proposed clean-slate network architectures centered around alternate first-class principals, such as content, services, or users. However, much like the hostcentric IP design, elevating one principal type above others hinders communication between other principals and inhibits the network's capability to evolve. This paper presents the eXpressive Internet Architecture (XIA), an architecture with native support for multiple principals and the ability to evolve its functionality to accommodate new, as yet unforeseen, principals over time. We present the results of our ongoing research motivated by and building on the XIA architecture, ranging from topics at the physical level ("how fast can XIA go") up through to the user level.

Users are enticed by decreasing hardware costs and greater availability of softwareComputer-aided graphics-display systems once were regarded as something of a cure in search of a disease. Though they easily fulfilled the old adage that a single picture-in this case, one generated or enhanced by computer-is worth a thousand words, efforts at practical applications were thwarted by limited software and by prohibitively high equipment costs. Now, both barriers to wide acceptance have been successfully surmounted. A wide range of available graphics displays provide high resolutions at steadily declining prices. They readily interface with computers and both accept graphics inputs and present graphics outputs in shades of gray or in color.Much of the progress in computer-graphics systems can be traced directly to advances in large-scale-integration and display-device technologies. Thanks to microprocessors and low-cost semiconductor memories, an increasing number of subsystem functions are being performed economically in a shrinking amount of equipment space, thereby making practical new levels of system sophistication.Recently available color cathode-ray tubes (CRTs) can display over 1000 lines on a 19-inch screen, and commercial light-emitting-diode (LED) displays have attained a density of 30 dots per inch on a 2-by 4-inch array. Though such relatively large and dense LED displays are quite expensive now, their availability suggests exciting uses when prices fall sufficiently. In particular, future generations of pocket calculators might well incorporate, on their back sides, large LED displays exhibiting calculated plots. Six major application areas Present computer-graphics applications entail rather large systems and, for the most part, break down into six general areas: • Management information • Scientific graphics • Command and control • Image processing • Real-time image generation • Electrical and mechanical designEach application area calls for markedly different hardware and software. So unique are those requirements that few existing systems can meet most of the demands posed by even a single class of applications. Computergraphics designers seeking wide uses for their systems have concentrated on high-level software. They have developed a number of programming languages that not Carl Machover Machover AssociatesMichael Neighbors, Charles Stuart B-K Dynamics only simplify equipment usage and increase graphicssystem versatility, but also reflect the display needs of widely diverse end-users.The best known graphics-display languages are those that perform plotting tasks for "passive" display systems (ones for which images cannot change rapidly from one frame to another, in contrast to "active" systems, which do have that capability). Bearing names such as DIS-SPLA, PLOT-10, and GINO-F, these Fortran-based languages excel in applications that require plots of extensive amounts of information, rather than those calling for a high degree of user interaction, as in light-pen systems. As a result, they are mos...

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