Data Descriptive Language for Shared Data (RFC0242)
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2019-Feb-13
Internet Society Requests For Comment (RFCs)
L. Haibt: AUTHOR [+1]
RFC 242 NIC 7672 Categories: D.4, D.7
DATA DESCRIPTIVE LANGUAGE FOR SHARED DATA
L. Haibt A. Mullery
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 precludes the use of a Network Standard Reprsentation.
The descriptive language assumes that data may have an...