rfc313.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.


RFC 313                Computer Based Instruction             March 1972


   Terminal access to the ARPA Network could be provided in the
   following ways:

      1.)  Single Terminals - over common carrier facilities to the
      nearest compatible HOST or TIP.

      2.)  Large Clusters - Simple single purpose TIP, or simple mini-
      computer supported in the network as far distant HOST.

      3.)  Small clusters - either of the above two depending on the
      length and intensity of expected use and the number or terminals
      in the cluster.

   In addition to the above general uses of a large General Purpose
   Computer Network, there are several specific classes of network
   resources that may be useful.

CENTRALIZED DATA STORAGE

   The effect of economy of scale could reduce costs for smaller CBI
   systems if they make use, through the network, of mass storage on
   larger systems.  If duplicate smaller systems are distributed in the
   field, then the centralized storage would have a multiplying effect
   on savings for lessons and lesson material, but special attention
   would have to be given to the file structure to permit efficient use
   of look ahead techniques for lessons, lesson segments, and individual
   student pages.

   For CMI data there are savings that go beyond the economy of scale.
   A single management system could be selected or built on a large
   service center machine to be used by CBI systems on the network, even
   though the operational CBI systems are supported by different
   manufacturers' hardware.  This would not only reduce the cost for
   programming and maintaining CMI systems, but also facilitate cross
   system analysis and intersystem comparison, even though each using
   system would have its own set of files.  The user of the network data
   reconfiguration service and data transfer protocol should make such
   operations feasible.

   This approach to CMI would assist in early development stages of
   course material by easing the problem of accessing data on past
   performance and norms.  In the case of geographically distributed
   testing, the evaluation team would have faster access to performance
   data.  Both the distribution and modification tasks seem cleaner
   since there is only one copy of the released version to be updated.

   If the trillion bit laser memory proposed for AMES becomes a reality,
   then the economy of scale argument can be expected to be dramatic.



O'Sullivan                                                      [Page 5]

RFC 313                Computer Based Instruction             March 1972


LANGUAGE PROCESSORS

   A basic characteristic of a large General Purpose Computer Network is
   that it is capable of providing support from various manufacturers'
   machines.  That is, such a network can be comprised of a number of
   special purpose processors that can be distributed geographically and
   organizationally to locations where the best support exists for each
   process.

   This characteristic makes it possible to select and join the best
   match of capabilities for a complex application .  It is no longer
   necessary to settle for a hardware/software system that does a
   reasonable job in most areas of the applications need.

   CBI is a complex application.  In addition to a good management
   system and associated data base, it requires heavy text handling for
   lesson material, table lookup and branching logic for acting on the
   student selected answers to multiple choice questions, a student
   arithmetic problem solving language for drill and practice,
   simulation capability of both physical processes (for laboratory and
   circuit simulation), and of decision processes (for gaming
   experience), and a future need for natural language processors to
   permit evaluation of free form student responses.  In addition, there
   may be need for heavy statistical and arithmetic processing for
   course, student, and instructor evaluation.

   Depending on the course, various mixes of languages to support the
   above activities will be needed.  Some believe that the language
   required for presentation of course material and evaluation of
   student response (and associated appropriate action) may be heavily
   dependent on the type of course being given.  As we develop a deeper
   understanding of the learning process, we are likely to require
   expansion of languages to provide new functions and perform processes
   not yet identified.

   To provide expandability of languages, Meta-compiler techniques can
   be applied.  Meta-compilers are in an early stage of development;
   however, several are available on the network.  In addition to
   facilitating language expansion with minimum effort while preserving
   the workability of code written in the previous versions of the
   changing language, the Meta-compiler can be made to produce either
   compiler or program object code that will operate on several
   different target machines.  This feature can give both programs and,
   in some cases, compilers that are transportable across machines,
   eliminating the need to settle on a single manufacturer's hardware
   when it is expected that a CBI compiler or interpreter, or a course
   or set of courses is going to be used in a way that requires




O'Sullivan                                                      [Page 6]

RFC 313                Computer Based Instruction             March 1972


   substantial geographic distribution.  Hardware decisions can be based
   on the most cost-effective hardware for the combinations to be run at
   one time.

   Use of Meta-compilers will permit the development and debugging of
   new course material in advance of the delivery of the system selected
   for operations, even though the selected machine is not yet
   represented in the large General Purpose Computer Network.  Field
   test can also proceed before the selected hardware arrives.

   Experience to date in the use of Meta-compilers indicates that the
   use of their high order languages to implement compilers and
   interpreters result in dramatic savings in both turnaround time and
   the absolute cost of producing a finished language product.

DIALOGUE SUPPORT SYSTEMS

   In a field developing as rapidly as CBI, and at a time when
   substantial implementation is about to take place, dialogue between
   theoreticians, developers, and users is an important issue.  New
   tools for supporting dialogue among members of a distributed group
   are currently in experimental use in the ARPA network.  These new
   techniques not only support dialogue more rapidly than the
   distribution of papers, notes, and memos, but in some cases tend to
   sharpen the thought process and yield a better result.

   The application of such facilities, when ready, will be helpful
   beyond the early planning stages or projects.  After plans are set,
   during the development of a project, a broader group of experts will
   be able to be called on to work on problems and questions as they
   occur.  Later, as the product is being field tested (especially if
   testing is distributed or separated from the evaluation group), these
   new tools can be used to allow the test implementors to interact with
   each other and with evaluators in a more timely manner than a post-
   mortum meeting, resolving problems and questions as they occur, and
   as a side benefit producing more complete documentation of test
   progress.

   After the tests, when the product is being used operationally, these
   same tools can provide an excellent vehicle for tapping the ideas,
   suggestions, and enrichments contributed by the more creative
   instructors, and facilitate acting on them more rapidly than is
   currently possible.

   Meanwhile, as these tools are being developed, present ARPA Network
   procedures for supporting the dialogue in a distributed group in more
   traditional ways may prove helpful.  The Network Information Center
   (NIC), in addition to supporting the general ARPANET community, is



O'Sullivan                                                      [Page 7]

RFC 313                Computer Based Instruction             March 1972


   supporting special interest groups such as the Speech Understanding
   Research (SUR) group.  The application of these procedures could
   establish a valuable link between the academic-nonprofit institutions
   working on CBI, the centers in the Armed Forces where development and
   operations are taking place, and members of the network community who
   have an intimate understanding of the network resources available.

CONCLUSION

   This paper has argued that there are resources in a large General
   Purpose Computer Network that can be applied to CBI with high
   utility.  The argument can be extended to suggest that large
   dedicated CBI systems can have greater utility to users (and in the
   other direction, greater use), if tied into a General Purpose
   Computer Network, with respect to current network capabilities,
   future network developments, and in some cases provide backup during
   periods of overload or system failure.

   There are certainly important CBI issues outstanding in areas of
   pedagogy, strategy, curriculum development, testing, etc.  As CBI
   systems are developed there are important issues of control (of the
   development process, of the distribution of material, and of
   modification of those materials).  However, these issues seem to be
   independent of the question of whether CBI takes advantage of the
   resources of a large General Purpose Network.

   There are important problems to be solved on the computer side
   dealing with better tools to handle and evaluate masses of data,
   language, and protocols for network utilization.

   However, there seems to be sufficient promise in what we know of
   present network capabilities to warrant serious consideration by the
   developers of CBI of how General Purpose Networks fit in, and by
   network people of how their resources apply to this important large
   application area.





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     [into the online RFC archives by H閘鑞e Morin, Viag閚ie 10/99]









O'Sullivan                                                      [Page 8]