for EmNets. Algorithms that optimize for certain resources, for example, and give near-optimal trade-offs between the various relevant resources will be very important. Designing and implementing algorithms that can both solve the problems EmNets will pose and be implementable within the constrained environment that EmNets will be operating in are likely to be a significant challenge. In addition, the question of how the quality of service might degrade in the presence of partial information (a likely scenario since it may not always be possible, owing to bandwidth or resource constraints, to have all the information) may well need to be answered. Current work on this sort of question deals with time-space trade-offs for computation and trade-offs between the quality of the solution and the precision of the input data, for example. EmNets present yet more kinds of trade-offs that will need to be addressed.

Finally, the examples discussed in this chapter share a characteristic—each identifies an assumption of the current computing model for networks that will not hold in the coming world of EmNets and proposes an alternative to that computing model based on a more reasonable assumption. As people attempt to build applications of EmNets, it will be important for them to identify suspicious assumptions or counterproductive abstractions in the current computing model, and to think of alternatives that can be built into the infrastructure for the application. Many more assumptions and abstractions will be identified than have been listed here. Funding agencies should watch for patterns in which researchers identify a doubtful assumption or abstraction, replace it with another that seems more useful in the context of the application, and determine if the new assumption or abstraction can be used in other applications.

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Computer Science and Telecommunications Board (CSTB), National Research Council. 1999. Trust in Cyberspace. Washington, D.C.: National Academy Press.


Freeman, Eric , Susanne Hupfer, and Ken Arnold. 1999. JavaSpaces Principles, Patterns, and Practice. Reading, Mass.: Addison-Wesley.


Object Management Group. 1991. Common Object Request Broker: Architecture and Specification. OMG Document No. 91.12.1.


Schneider, F.B. 1993. “What good are models and what models are good?” Distributed Systems, 2nd ed., S.J. Mullender, ed. Reading, Mass.: Addison-Wesley.


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