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+Network Working, Group                                P.M. Karp, MITRE
+Request for Comments #146                             D.B. McKay, IBM
+NIC 6742                                              D.C. Wood, MITRE
+                                                      12 May 1971
+
+Categories: D.4, D.7
+Obsoletes: none
+Updates: none
+
+
+                Views on Issues Relevant to Data Sharing
+                          on Computer Networks
+
+
+Introduction
+
+The formation of a committee to address the problems of achieving
+data sharing on the ARPA Network, as suggested by Arie Shoshani
+(RFC #140) is desirable at this point of network development.  We
+concur with Shoshani's ideas (presented in an introductory paper
+to the network data sharing meeting, scheduled for Tuesday, May 18)
+and believe that purpose of the committee should be -
+
+        a) to classify the issues involved and to propose various
+           approaches;
+
+        b) to integrate the hitherto independent network activities
+           that address problems in the area of data sharing, and;
+
+        c) to set up and coordinate appropriate experiments to test
+           the services developed and to evaluate alternative
+           approaches.
+
+This position paper is intended to augment Shoshani's as a basis
+for discussion at the data sharing meeting. No attempt is made
+to discuss specific means of implementation since many approaches
+to data handling problems are possible and have been proposed.
+Rather, our viewpoint on what the committee's role should be in
+giving some cohesion to various existing implementations is
+presented.
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+                                                                [Page 1]
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+Our Views
+
+    One approach to achieving data sharing on the ARPA Network can
+be thought of as having three stages, which roughly correspond to
+the modes of use or operation. Within each stage are various levels
+of development required to get to the next stage. This development
+is not necessarily sequential. A description of the three stages
+follows.
+
+Stage 1: Data handling services are provided at various Hosts.
+         The user talks directly to the serving Host (via TELNET
+         or by addressing a known socket) to explicitly access
+         the service.  This mode of operation corresponds to
+         Bhushan's category of "direct" usage (RFC #114).  The
+         data services provided by the serving Host range from
+         simple ones, such as White's file transfer system (RFC #122)
+         to sophisticated systems such as the CCA's data machine
+         (NIC 5791 and 6706).
+
+Stage 2: The user has access to an intermediate process or data
+         control facility* that routes his requests for a particular
+         data service to the serving system. The user must explicitly
+         identify the data services to the used.  This mode of
+         operation corresponds to Bhushan's category of "indirect"
+         access. The data control facility provides the necessary
+         control commands, data transformations, and accessing
+         methods. A single request would include the use of several
+         interacting services. For example, Heafner's Data
+         Reconfiguration Service (RFC #l38) could be used in
+         conjunction with the use of CCA's data machine.
+
+
+
+
+
+
+_______________
+*The data control facility is not necessarily located at his local
+Host. Such a facility may exist on from one to all Host (i.e.,
+ranging from centralized to completely distributed).
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+                                                                [Page 2]
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+Stage 3: The user treats the network as a single resource and is
+         unconcerned with the location of the services, data files,
+         etc. All references are by name. In this mode of opera-
+         tion, the data control facility can function as a referral
+         center for data service requests by using the most ap-
+         propriate data service available and by automatically
+         combining the use of several services that may be needed
+         to satisfy a request.  For example, data could be retrieved
+         from several files, each managed by a different data
+         management system. The data control facility must be
+         cognizant of the location of data files, their structure,
+         data management system capabilities, etc.
+
+Some approaches to the design of the data control facility have
+been suggested by Shoshani, notably the integrated data management
+system (IDMS) and the unified data management system (UDMS). The
+notion of the network machine (RFC #51) is closest to the capabilities
+one would see in Stage 3.
+
+Relevant Areas of Development
+
+The data control facility can range anywhere from a simple inter-
+face to an intelligent front-end processor to a network-wide re-
+ferral system.  In any case, a common means is desirable for
+handling applications such as file transfer, on-line update and
+retrieval of data, information gathering and reporting, and program
+access to data. To attain this end, a few of the areas in which
+developments will be required include:
+
+     a)  a data description language, permitting the user to define
+         the physical structure of files, to define logical files,
+         and to categorize data fields for name referencing. The
+         language should be designed to facilitate the resolution of
+         physical discrepancies in data and file structures. The
+         user should be able to superimpose logical restructuring of
+         data without any change in the physical structure.
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+                                                                [Page 3]
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+b) a control or access language that can be mapped into
+         various data management languages. Considered here is
+         Shoshani's suggested two-level approach with perhaps a
+         meta-language implementation to facilitate conversions
+         among already existing languages.
+
+     c)  methods for managing and merging distributed data, search
+         mechanisms for file directories, error recovery techniques,
+         etc.
+
+Independent ARPA Network activities that in effect constitute
+Stage 1 have touched on these areas and should be incorporated into
+the overall data sharing scheme such that all of the isolated
+pieces are compatible.  For example,
+
+      a) the data reconfiguration service (RFC #138) would be
+invoked by the data control facility whenever data transformations
+are required.
+
+      b) the file transfer protocol (RFC #114, #122)
+should be consistent with other data handling services.
+
+      c) CCA's data machine should be a subset or part of any data
+control facility. The network data language and set of data
+management services that they plan to implement can perhaps be
+adopted network-wide.
+
+      d) the network machine concept (RFC #51) for defining the pro-
+gram and data environments should be resurrected. The data control
+facility should be a subset of a network machine architecture.
+
+Some other relevant topics include NIL (RFC #51), DEL (RFC 5), the
+notion Of MYLOCAL n, YOUR LOCAL n, and STANDARD n (RFC #42), user
+level protocol objectives as described in RFC #76 and #91.
+
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+                                                                [Page 4]
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+Experimentation and Testing
+---------------------------
+
+As data services are developed on the network, a coordinated
+effort is desirable
+
+     a)  to exercise individual implementations to see
+         if they work, both alone and in conjunction with
+         other data services, and
+
+     b)  to evaluate alternative approaches.
+
+Some examples of experimentation to test data services follow:
+
+     1.  File Transfer Protocol
+
+         The file transfer protocol should be used to
+         manipulate data files controlled by various
+         systems.
+
+     2.  Data Transfer to Data Computer
+
+         The ability to transfer existing data bases and
+         their structures onto the data computer should be
+         demonstrated.
+
+     3.  Data Restructuring
+
+         The ability to define logical restructuring of
+         data for users needs which would be accessible by
+         name should be demonstrated. The original physical
+         structure would be maintained.
+
+     4.  Data Transformation
+
+         The ability to access various data management
+         systems on the network without the user being
+         concerned with the data transformation involved
+         should be demonstrated. Necessary calls to forms
+         available on the Data Reconfiguration Service
+         should be handled automatically and should be
+         transparent to the user.
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+                                                                [Page 5]
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+5.  Data Consistency
+
+         Problems of maintaining consistency when duplicate
+         copies of a data file exist and updates to the file
+         are made should be investigated. Automatic use of
+         file transfer protocol and DRS to generate new
+         duplicate copies should be included.
+
+     6.  Data Privacy
+
+         Access controls for privacy Of data files in the
+         network environment should be designed and evaluated.
+         This includes controls on parts of distributed files.
+
+Our recommendation is that the committee on data sharing be
+responsible for coordinating development in these areas, for
+attempting to maintain consistency among data services, and for
+testing services in a series of experiments as they are implemented.
+
+
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+
+
+       [ This RFC was put into machine readable form for entry ]
+       [ into the online RFC archives by BBN Corp. under the   ]
+       [ direction of Alex McKenzie.                   12/96   ]
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+                                                                [Page 6]
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