Integrated Project Support Environments. The Aspect Project

282 Pages·1991·4.562 MB·English

by  Alan W. Brown (Eds.)

The A.P.I.C. Series
No 33
Integrated Project
Support Environments
The Aspect Project
Edited by
ALAN W. BROWN
Department of Computer Science,
University of York, Heslington, England
ACADEMIC PRESS
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Foreword
An important plank of the Alvey Programme on IT Research and Development was
the proposition that the use of Software Engineering Tools and Methods would be
advanced by producing a series of Integrated Project Support Environments. These
would provide integrated support throughout the software life-cycle for the
designers, implementors and eventually for the systems maintainers. Three genera-
tions of IPSEs were planned, respectively to be file based, data based, and
knowledge based systems, and it was expected that full development of these pro-
jects would need up to ten years to come to fruition.
The eventual outcome was that three major projects were launched, each of four
years duration; Aspect, Eclipse, and IPSE 2.5. Each investigated different
approaches to the issue of building a useful IPSE; in the case of Aspect the central
design choice was to base the system around a relational database.
We are now in the post-Alvey era and it is time to evaluate what has been achieved
in order to derive the maximum possible benefit from the substantial investments
made in the Alvey Programme. It is important to publish the results as widely as
possible.
I welcome this book as a substantial contribution to this task. Publication as a book
gives a valuable opportunity to study the project as a whole in a coherent way which
separate papers would not achieve. The co-operation necessary to produce it
demonstrates the continuing benefits of the style of co-operative working between
partners both from industry and academia which was brought about in large meas-
ure by the Alvey programme. It is, in my opinion, well worth study by all con-
cerned with the development of large software systems.
Professor J.N. Buxton
Director, Systems Engineering
Information Technology Division
Department of Trade and Industry
Preface
Over the past twenty years many large scale software development projects have
been notorious for being behind schedule, over-budget, and producing a low quality
end-product. Indeed, it has been suggested [14,42] that:
• at least 15 per cent of all software projects never deliver anything; that is, they
fail utterly to achieve their established goals;
• overruns of 100 and 200 per cent are common in software projects;
• the cost of maintaining a software system is typically more than twice the ori-
ginal development cost.
Given the large amounts of money which are being spent on software development
(for example, it is estimated that in the USA over 50 billion dollars were spent on
software development and maintenance in 1987), there is clearly a need for a better
approach to building such systems.
One approach which seems to offer hope to large scale software developers is
to provide automated support for the development process whenever possible. The
aim of this approach is to develop an Integrated Project Support Environment
(IPSE) which helps control and coordinate the many tasks which must take place
within a large software project.
The Aspect project, started in 1984, was directly concerned with investigating
issues involved in realising a practical, cooperative IPSE. This book provides an
overview of the work carried out on the Aspect project, with particular attention
focussed on a prototype IPSE implementation which was developed in order to
evaluate some of the Aspect concepts.
The Organisation of the Book
The book starts with a discussion of the software crisis, and introduces IPSE tech-
nology in general as a possible solution. This is followed by an overview of the
approach taken by the Aspect project to building an IPSE, illustrated by a demons-
tration of a prototype Aspect IPSE. Each technical area studied by the Aspect pro-
ject is then discussed in depth. Finally, the achievements of Aspect are put into a
wider software engineering context by comparing them with other work in the IPSE
8 Integrated Project Support Environments: The Aspect Project
area.
Due to the large, diverse, and collaborative nature of the Aspect project, the
book is organised as a collection of individual papers describing many of the speci-
alised areas which were examined in the project. Note that the use of a large
number of authors in writing the chapters of this book has inevitably resulted in a
variation in the styles and approaches used for each chapter. However, far from
being a drawback of the multi-author approach, we believe that this has encouraged
the use of a style which is most appropriate to the material being discussed. Hence,
each chapter conveys its subject matter in the most the suitable format, ranging
from high-level descriptions in Chapters 1, 2 and 3, to formal definition in the Ζ
specification language in the case of Chapter 10.
The Structure of the Book
The book divides into five main parts.
Parti
The first part comprises Chapters 1, 2, 3 and 4 and provides an introduction and
overview of IPSE technology in general, and the work carried out by Aspect in par-
ticular.
• Chapter 1 is a general introduction to the Aspect project, describing the back-
ground, funding and organisation of the project.
• Chapter 2 argues the need for an IPSE, and describes the basic architectural
principles of current work on IPSEs. The basic requirements for an IPSE are
reviewed, and previous attempts at tool development are briefly discussed.
The issue of tool integration is then developed in more detail.
• Chapter 3 provides an overview of the main aims and approach of the Aspect
project, and describes the architecture adopted for the Aspect IPSE.
• Chapter 4 gives details of the demonstration example which is used to illus-
trate some of the later descriptions of the Aspect IPSE technology.
Part 2
The next three parts of the book deal with the technology of building an Aspect
IPSE. Each part concentrates on the details of the conceptual design and implemen-
tation of the component Aspect technologies. Part 2 is concerned with the central
database, or information base, which forms the heart of an Aspect IPSE.
• Chapter 5, the Information Base Engine, describes how the information base
is built on top of a relational database using Codd's extended relational model
RM/T to provide the enhanced semantic features required.
• Chapter 6, the Information Base Superstructure, describes facilities to sup-
port the software development process which we believe will be common to
any IPSE that might be configured within the Aspect framework. These
include task (or, activity) definition and planning, the view mechanism which
provides an object-oriented abstract environment, the rule mechanism, the
publication mechanism, configuration management, and version control.
Preface 9
Part 3
In the third part of the book, the important user interface work of the Aspect project
is discussed in detail.
• Chapter 7, Human Computer Interface Perspectives, describes the overall
philosophy of that part of the architecture which handles the interface to users.
• Chapter 8 describes in detail the user interface component of the Aspect
IPSE known as the Presenter.
• Chapter 9 describes the Doubleview tool. This is an interactive tool for
quickly developing user interfaces using the Aspect Presenter.
Part 4
The fourth part of the book examines the work on supporting host/target software
development which was an important component of the Aspect project.
• Chapter 10 describes the work on host/target debugging of distributed Ada
programs. The development of real-time application software (such as avion-
ics systems) is a major driving force of much of the current work in IPSEs.
Part 5
The final part of the book summarises the achievements of the Aspect project, and
attempts to place the Aspect work in the context of current IPSE developments.
• Chapter 11 examines work on PCTE, CAIS and ATIS, relating it to the work
that was carried out in the Aspect Project.
• Chapter 12 summarises the achievements of the Aspect project, and draws
comparisons with other Alvey-funded IPSE projects.
Acknowledgements
As a large collaborative project, there have been many people who have had a direct
influence on the Aspect Project. In addition to the contributors to this book, we ack-
nowledge the work of a number of others:
• At SD-Scicon, Anthony Hall (now with Praxis Ltd.) and Dave Robinson were
particularly influential. Both acted as technical architects for the project, and
as such made major contributions to the success of the Aspect project. Peter
Rusling (now with Systematica) smoothed the running of the project by deal-
ing with much of the administration, and was responsible for overseeing much
of the work on Perspective Kernel.
• At MARI, work on the distribution of the information base was carried out by
a large number of people over the lifetime of the project. These included Phil
Fisher, Anirban Bhattacharyya, Rachel Wilmer, Anthony Davies, and Sidney
Burness.
• At York, Ben Dillistone (now with Praxis Ltd.) was responsible for much of
the early work on the Aspect version control and configuration management
system.
10 Integrated Project Support Environments: The Aspect Project
• Ian Wand was in overall charge of the work carried out at York, and Brian
Randell performed a similar role at Newcastle.
The work described in this book was supported by the Science and Engineer-
ing Research Council (SERC) through the Alvey Software Engineering Directorate
under a number of grants, including:
GR/C/98092 - Research and Development Leading to a Distributed Integrated Pro-
ject Support Environment (1st July 1984 to 31st October 1987).
GR/E/05353 and GR/E/06398 - Aspect Two: Centrally procured equipment (1st
November 1986 to 31st October 1987).
GR/D/86041 - SE Computing Facilities to Support Additional Research in IPSE's
(1st February 1986 to 31st January 1987).
GR/E/42303 and GR/E/42082 - SE/170 Aspect Change II (1st July 1987 to 31st
March 1989).
Finally, my thanks to Alison Pearcy and Robert Stroud who were particularly active
in providing me with help during the editing process for this book. The final form
of the book has been greatly enhanced by their work, particularly Robert's diligent
reviewing of the final drafts of the book.
Alan W. Brown
University of York
List of Contributors
Ian D. Benest University of York
Alan W. Brown University of York
Anthony N. Earl Hewlett-Packard Laboratories
Peter Hitchcock University of York
Sylvia J. Holmes University of York
Andy D. Hutcheon University of York
Alison Pearcy University of York
Ann Petrie University of Newcastle upon Tyne
David S. Snowden University of York
Robert J. Stroud University of Newcastle upon Tyne
Roger K. Took University of York
Ray A. Weedon Open University
Andy J. Wellings University of York
Richard P. Whittington Hand, Whittington and Associates
The work reported in this book was carried out while the above contributors were
employed by the Universities of York and/or Newcastle upon Tyne.
Chapter 1
Introduction
P. Hitchcock and AW. Brown
1.1 Project History
The Aspect project had its origins in March 1982, when Mr. Kenneth Baker, the
Minister for information technology in the United Kingdom, set up a committee to
advise on the scope of a collaborative research programme in Information Technol-
ogy (IT). This committee was formed as a direct result of the unveiling, in October
1981, of the Japanese Fifth Generation Computer Programme, which was seen to
pose a major competitive threat to the UK IT industry. The Committee, chaired by
John Alvey, produced its report in the summer of 1982, which became known as the
Alvey Report.
The Alvey report recommended a five-year programme to mobilise the UK's
technical strengths in IT by setting up collaborative projects between industry, the
academic sector and other research organisations. The cost would be 350 million
pounds with the Government contributing two-thirds of the direct cost of the pro-
gramme. Four areas of work were identified: software engineering, man-machine
interfaces, intelligent knowledge based systems and very large scale integration.
Within these areas of work the emphasis was to be on the core enabling technolo-
gies. For software engineering this was the concept of the Information Systems
Factory (ISF). The ISF would provide an integrated set of tools for producing IT
systems using software engineering techniques and would be developed from suc-
cessive generations of Integrated Project Support Environments (IPSEs), start-
ing with a consolidated set of the tools that were currently available.
14 Integrated Project Support Environments: The Aspect Project
The Alvey Report identified three generations of project support environment:
1. The first generation IPSEs consisted of separate tools which interacted at the
file level. The Unix operating system and its associated tools was a good
example of this approach.
2. Second generation IPSEs were to be developed around suitable database sys-
tems. Information would be shared at a finer granularity than was possible
with the file based technology used by first generation IPSEs. In addition, it
would be possible to hold in the database descriptions of the data as well as
the actual data itself.
3. The third generation IPSE was the Information Systems Factory which would
introduce the more powerful facilities of a knowledge base to a second gen-
eration IPSE.
The time-scale was that the ISF should be available by year 6 of the pro-
gramme.
The Alvey Report was accepted by the Government and three IPSE projects
were started. These were Aspect, Eclipse [17], and IPSE 2.5 [93]. Both Aspect and
Eclipse are examples of second generation IPSEs. Eclipse was developed using the
Portable Common Tool Environment (PCTE) [27], an Esprit project funded by the
European Economic Commission. IPSE 2.5, as its name suggests, is a further step-
ping stone along the route towards an ISF, in this case investigating support for for-
mal methods and the incorporation of knowledge based system techniques.
The Aspect project itself started in January 1984. It was a collaborative ven-
ture between four industrial companies and two Universities, and was the first con-
tract to be awarded by the Alvey Software Engineering Directorate. The proposed
work plan for the first three years of Aspect amounted to 80 person years, for which
an initial grant of over two million pounds was awarded.* System Designers PLC
(now SD-Scicon) led the Aspect project as the prime contractor during its primary
three year term. The other industrial partners were International Computers Limited
(ICL), GEC Computers Limited, and MARI Advanced Electronics Limited. The
academic partners were the Universities of York and Newcastle upon Tyne.
1.2 The Aim of the Aspect Project
The aim of Aspect was to carry out research into second generation IPSE technol-
ogy, and to demonstrate and evaluate the results of the research through a number of
prototype IPSEs supporting the distributed development of large scale software sys-
tems. Aspect was particularly interested in support for multi-language program-
ming, host-target working, and any prototype would give support to all stages of
the software development process.
Aspect has produced two such environments. The first is a prototype IPSE
framework embodying advanced research in key areas. This is the prototype which
forms the basis for discussion in this book, and is subsequently referred to as "the
Aspect IPSE". The second is an exploitable commercial IPSE framework, called
* The Alvey funding rules were that the Universities received all of their direct costs, and the
industrial partners, one half.