Data Descriptive Language for Shared Data (RFC0242)
Original Publication Date: 1971-Jul-19
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
L. Haibt: AUTHOR [+2]
A primary consequence of the use of networks of computers is the demand for more efficient shared use of data.
Categories: D.4, D.7
DATA DESCRIPTIVE LANGUAGE FOR SHARED DATA
Thomas J. Watson Research Center
Yorktown Heights, N.Y.
July 19, 1971
A primary consequence of the use of networks of computers is the
demand for more efficient shared use of data.
Many of the impedements to easy shared data follow from the many
diverse ways of representing and making reference to the same data.
Almost all of these problems have been known before data was shared
through computer networks, but the network facility has simply
emphasized the problems.
For convenience of discussion, representation differences will be
classified in three categories. The first category is one of very local
representation - the bit patterns for the character set, for fixed point
and floating point numbers. These differences are usually imposed by
differences in CPU's and storage devices. Translations from one
representation to another at another at this level can usually be made a
unit at a time (e.g. computer word by computer word) with the most
serious problems occurring when there are some values in one
representation scheme which have no corresponding meaning in the other
representation scheme, as, for expamble, when trying to translate
eight-bit bytes to six-bit bytes.
A second category of differences has to do with the representation
of collections of data, e.g., their size, ordering and location.
A third category of representation differences which is a little
difficult to characterize has to do with all the more complex structures
that data collections may have - for example, files with indexes, fields
with internal pointers and cross references, and collections of files
such as partitioned data sets and generation data sets in OS 360.
The approach to coping with these problems within our project of
Network/440 has been to work on the development of a descriptive
language which would permit the specification of those aspects of data
representation which would be subject to transformation in moving data
about in a network. Then, the network data managment system would be
able to refer to the descriptions as needed in the data management
function. For example, to a large extent, one could supply two
descriptions to the data manager, one wich indicates how data is now
represented, and one which indicates how a copy of it should look, and
the data managment systems could invoke the necessary transformations to
make the proper copy.
This approach to specifying data transformation contrasts somewhat
with systems, such as the RAND Form Machine, which provide a formalism
for specifying the particular translation alogrithms for changing form
one form to another. the descriptor-to descriptor approach seems to
simplyfy the programming burden when creating new field formats. Neither
method of specifying translations preclud...