between programming languages;
by non-programmers.
Must provide reference to externally-defined syntaxes.
Must be flexible, contractable, and expandable to allow the DDR
to be built with a minimum of overhead.
Must be able to be written with standard word processors.
These will not be belabored here. Suffice it to say, that the TSDN has
been designed to try to meet these requirements and attributes.
Specifically, the TSDN permits the sender to describe the transferred
information and to send this description separately or as an integral part
of the transfer file. It permits the description of both character and
bit field information in fixed- (without delimiters) or variable-width
(delimited) fields or subfields. It further permits the identification
of fields and subfields by arbitrarily long names and labels which serve
to give meaning to the data. In addition, it provides for the
definition and labeling of complex structures and commutated data.
The Goal
The intent is to supply the data product user with the conceptual or
logical description of the data as well as the format and representation of
the data. This information may be packaged with the data such that a suite
of standard software at the user’s installation can transform the data to
conform to his machine architecture and can present standard views for
applications.
Why is Something New Needed ?
Type declarations in programming languages define the element formats as
they occur within the closed system of the hardware/operating system
housing the analysis program. Inasmuch as these declarations are different
from language to language, and do not pretend to describe the formats as
the data are transferred, a common notation for describing the data during
interchange is required.
The Problem
Analysts may be expected to work in an environment in which there is a need
to retrieve data from various files, either local or in archives, generated
recently or decades ago, and to present that data to the analysis system in
a usable, verified form. The files may be expected to be in various
formats, using various numerical representations. The applications
requiring the data may be expected to be in any one of a number of
languages. For the system to be useful, a simple and consistent interface
to the user programs is needed. Such an interface should be able to
respond to a request from a user analysis program containing elements such
as:
retrieve
from
name
format
91
