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Technological Assessments

Appendix Technologies for Distributed Systems contains an analysis of the main technologies, systems and languages that are relevant to building geographically distributed multi-user applications and that are projected to play a major role in the mid-term future. In a nutshell, this analysis leads us to the following assessments:

Coordination Languages
While a large number of coordination languages have been proposed and developed, there is no empirical evidence for the a priori superiority of any particular model. We consequently believe that the coordination model should be based on the demands of the application domain.
Java is de facto the Internet programming language with a large number of vendors providing technologies and compatible systems. It is extremely portable and available on practically every existing system; JNI provides an interface to external C/C++ code. Despite of its known problems (efficiency, security versus flexibility), it would be foolish not to utilize the existing technology base wherever possible. ActiveX, the main competing technology, will also play an important role but its future outside the Microsoft world is insecure.
Information Services
The WWW conceptually provides the worlds largest network database but without the structuring and management facilities of a real databases. HyperWave is based on a much better organization concept for providing distributed information services; its multi-protocol support allows to access most of its features also from conventional WWW browsers. Its commercial support and its fairly large user base ensure future reliability and availability.
Distributed Objects
CORBA/OpenDoc are currently the industry standards for building distributed object-based services. Java RMI and JavaBeans provide similar services for Java-based environments; Java IDL represents an interface to the OMG standards. The Microsoft technologies DCOM/ActiveX play a similar role for Windows/Intel systems but their future support as an "open standard" by other vendors is uncertain.
Network Services
The Argonne Nexus system is a stable basis for building distributed services. However, its primary purpose is to serve as a runtime system for parallel languages and communication libraries; correspondingly its interface provides rather low-level concepts like threads, global pointers, and remote service requests. On the other hand, the Caltech Infospheres Infrastructure has been primarily designed to build distributed applications on the basis of the Internet infrastructure leveraging open standards in the WWW/Java world. The system is still in its beta stage but the prospects seem promising. The European PageSpace effort pursues similar goals but its reliance on tuplespaces as the basic communication mechanism may result in efficiency problems. Technologies for mobile agent transfer like the IBM Aglets Workbench might be integrated into II or PageSpace.
Collaborative Environments
The commercial market is still mainly focused on groupware supporting the needs of centrally located medium-sized enterprises. There exist already various research prototypes for distributed virtual reality, concurrent engineering, and virtual classrooms (the later mostly limited to video conferencing), but few systems are usable for real-world applications and most of them are based on proprietary technologies.

Based on this analysis, we sketch in the next subsection a possible implementation strategy for our architectural framework.

Maintainer: Wolfgang Schreiner
Last Modification: March 11, 1997

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