rfc610.txt

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Network Working Group        Richard Winter, Jeffrey Hill, Warren Greiff
RFC # 610                                                            CCA
NIC # 21352                                            December 15, 1973










                  Further Datalanguage Design Concepts










                             Richard Winter
                              Jeffrey Hill
                             Warren Greiff








                    Computer Corporation of America
                           December 15, 1973














Winter, Hill & Greiff                                           [Page 1]

RFC 610           Further Datalanguage Design Concepts     December 1973


                             Acknowledgment

During the course of the Datacomputer Project, many people have
contributed to the development of datalanguage.

The suggestions and criticisms of Dr. Gordon Everest (University of
Minnesota), Dr. Robert Taylor (University of Massachusetts), Professor
Thomas Cheatham (Harvard University) and Professor George Mealy (Harvard
University) have been particularly useful.

Within CCA, several people in addition to the authors have participated
in the language design at various stages of the project. Hal Murray,
Bill Bush, David Shipman and Dale Stern have been especially helpful.






































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RFC 610           Further Datalanguage Design Concepts     December 1973


1.  Introduction


1.1 The Datacomputer System

The datacomputer is a large-scale data utility system, offering data
storage and data management services to other computers.

The datacomputer differs from traditional data management systems in
several ways.

First, it is implemented on dedicated hardware, and comprises a separate
computing system specialized for data management.

Second, the system is implemented on a large scale. Data is intended to
be stored on mass storage devices, with capacities in the range of a
trillion bits.  Files on the order of one hundred billion bits are to be
kept online.

Third, it is intended to support sharing of data among processes
operating in diverse environments.  That is, the programs which share a
given data base may be written in different languages, execute on
different hardware under different operating systems, and support end
users with radically different requirements.  To enable such shared use
of a data base, transformations between various hardware representations
and data structuring concepts must be achieved.

Finally, the datacomputer is designed to function smoothly as a
component of a much larger system: a computer network.  In a computer
network, the datacomputer is a node specialized for data management, and
acting as a data utility for the other nodes.  The Arpanet, for which
the datacomputer is being developed, is an international network which
has over 60 nodes.  Of these, some are presently specialized for
terminal handling, others are specialized for computation (e.g., the
ILLIAC IV), some are general purpose service nodes (e.g., MULTICS) and
one (CCA) is specialized for data management.


1.2 Datalanguage

Datalanguage is the language in which all requests to the datacomputer
are stated.  It includes facilities for data description and creation,
for retrieval of or changes to stored data, and for access to a variety
of auxiliary facilities and services.  In datalanguage it is possible to
specify any operation the datacomputer is capable of performing.
Datalanguage is the only language accepted by the datacomputer and is
the exclusive means of access to data and services.




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RFC 610           Further Datalanguage Design Concepts     December 1973


1.3 Present Design Effort

We are now engaged in developing complete specifications for
datalanguage; this is the second iteration in the language design
process.

A smaller, initial design effort developed some concepts and principles
which are described in the third working paper in this series.  These
have been used as the basis of software implementations resulting in an
initial network service capability.  A user manual for this system was
published as working paper number 7.

As a result of experience gained in implementation and service, through
further study of user requirements and work with potential users, and
through investigation of other work in the data management field, quite
a few ideas have been developed for the improvement of datalanguage.
These are being assimilated into the language design in the iteration
now in progress.

When the language design is complete, it will be incorporated into the
existing software (requiring changes to the language compiler, but
having little impact on the rest of the system).

Datacomputer users will first have access to the new language during
1975.


1.4 Purpose of this Paper

This paper presents concepts and preliminary results, rather than a
completed design.  There are two reasons for publishing now.

The first is to provide information to those planning to use the
datacomputer.  They may benefit from knowledge of our intentions for
development.

The second is to enable system and language designers to comment on our
work before the design is frozen.


1.5 Organization of the Paper

The remainder of the paper is divided into four sections.

Section 2 discusses the most global considerations for language design.
This comprises our view of the problem; it has influenced our work to
date and will determine most of our actions in completion of the design.
This section provides background for section 3, and reviews some



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RFC 610           Further Datalanguage Design Concepts     December 1973


material that will be familiar to those who have been following our work
closely.

Section 3 discusses some of the specific issues we have worked on.  The
emphasis is on solutions and options for solution.

In sections 2 and 3 we are presenting our "top-down" work: this is the
thinking we have done based on known requirements and our conception of
the desirable properties of datalanguage.

We have also been working from the opposite end, developing the
primitives from which to construct the language.  Section 4 presents our
work in this area: a model datacomputer which will ultimately provide a
precise semantic definition of datalanguage.  Section 4 explains that
part of the model which is complete, and relates this to our other work.

Section 5 discusses work that remains, both on the model and in our
top-down analysis.

































Winter, Hill & Greiff                                           [Page 5]

RFC 610           Further Datalanguage Design Concepts     December 1973


2.  Considerations for Language Design


2.1 Introduction

Data management is the task of managing data as a resource, independent
of hardware and applications programs.  It can be divided it into five
major sub-tasks:

    (1) _creating_ databases in storage,
    (2) making the data _available_ (e.g., satisfying queries),
    (3) _maintaining_ the data as information is added, deleted and
        modified,
    (4) assuring the _integrity_ of the data (e.g., through backup and
        recovery systems, through internal consistency checks),
    (5) _regulating_access_, to protect the databases, the system, and
        the privacy of users.

These are the major data-related functions of the datacomputer; while