Table Of ContentComputer-Supported Cooperative Work
Springer-Verlag Berlin Heidelberg GmbH
Uwe M. Borghoff Johann H. Schlichter
Computer- Supported
Cooperative Work
Introduction to Distributed Applications
With 203 Figures and 18 rabIes
, Springer
Prof. Dr. Uwe M. Borghoff
Institute of Software Technology
University of the Federal Armed Forces Munich
Werner-Heisenberg -Weg 39
85579 Neubiberg, Germany
[email protected]
Prof. Dr. Johann H. Schlichter
Department of Computer Science
Technical University of Munich
Arcisstr.21
80333 Munich, Germany
[email protected]
Library of Congress Cataloging-in-Publication Data applied for
Die Deutsche Bibliothek -CIP-Einheitsaufnahme
Borghoff, Uwe M.:
Computer supported cooperative work: introduction to distributed
applications/Uwe M. Borghoff; Johann H. Schlichter. - Berlin;
Heidelberg; New York; Barcelona; Hong Kong; London; Milan;
Paris; Singapore; Tokyo: Springer, 2000
ACM Computing Classification (1998): H.5.3, H.4.1, C.2.4, D.2.9,
D.2.12, F.1.2, K.4.3, K.6.4
ISBN 978-3-642-08631-1 ISBN 978-3-662-04232-8 (eBook)
DOI 10.1007/978-3-662-04232-8
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e Springer-Verlag Berlin Heidelberg 2000
Originally published by Springer-Verlag Berlin Heidelberg New York in 2000.
Softcover reprint ofthe hardcover 1st edition 2000
The use of general descriptive names, trademarks, etc. in this publication does not imply,
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Preface
The terms groupware and CSCW (computer-supported cooperative work)
have received significant attention in computer science and related disciplines
for quite some time now. This book is a revised and extended version of the
2nd edition of the German textbook "Rechnergestützte Gruppenarbeit: Eine
Einführung in verteilte Anwendungen". It has two main objectives: first, to
outline the meaning of both terms, and second, to point out both the numer
ous opportunities for users of groupware and the risks of applying such sys
tems. The book intends to introduce an area of distributed systems, namely
the computer support of individuals trying to solve a common problem in
cooperation with each other but not necessarily having identical work pi aces
or working times.
Computer-supported cooperative work is an interdisciplinary application
domain. It can be viewed as a synergism between the areas of distributed sys
tems and (multimedia-) communication on the one hand and between those
of information science and socio-organizational theory on the other hand.
Thus, the book is meant to help students of aH these disciplines, as weH as
users and developers of systems which have communication and cooperation
within groups as top priorities.
Structure of the book. The book is divided into three main parts. The first
part contains two chapters and introduces distributed systems and computer
supported cooperative work (groupware). Many of the fundamental prin
ciples of distributed systems play an important role in CSCW. Therefore,
in Chapter 1 we briefty introduce these principles as they are relevant
to the understanding of the distribution aspects of CSCW. We discuss the
key concept of transparency and typical communication mechanisms such
as information sharing, message exchange, bi-directional communication and
producer-consumer interaction. Moreover, as part of the discussion of the
widely-accepted dient-server model, we introduce the remote procedure caH
(RPC) as a means of processing service requests. We describe in detail RPC
properties, the structure of RPC messages, and the fundamental mechanisms
of RPC languages. AdditionaHy, we also introduce object-oriented systems
and show how objects of such systems can be distributed among the differ
ent participating sites. The description of distributed applications focuses on
VI Preface
group communication and the design of distributed applications built accord
ing to the ODP framework.
Contemporary literature is overflowing with technical terms defining var
ious aspects of computer-supported cooperative work. In Chapter 2 we in
troduce these terms and discuss them with respect to practical teamwork
support. In addition to demonstrating typical usage scenarios and their char
acteristics, we also present several classification models, in particular the time
space taxonomy. When dealing with the so-called application level classifica
tion, we discuss message systems, group editors, electronic meeting rooms,
conferencing systems, shared information spaces, intelligent agents, and co
ordination systems. Furthermore, we investigate factors which contribute
to the success or failure of groupware systems. Research and experiments
with computer-supported cooperative work in real environments support this
work. The results of these studies demonstrate how groupware should be de
signed and how CSCW concepts should be validated. With Lotus Notes we
present one of the most successful groupware systems.
The second part of the book is subdivided into three chapters and deals
with some basic concepts of computer-supported cooperative work, including
group processes, concurrency control, and replication. The group process is
a fundamental CSCW concept which specifies the goals and structure of the
team as weIl as the progress of the cooperation between team members. In
Chapter 3 we discuss the centralized, the distributed nonreplicated, and the
distributed replicated group process models. After an introduction to a gen
eral cluster model, we explain strategies for distributing information within
and between clusters. Special attention is given to possible structures of asyn
chronous team interaction. The management of a shared context is a further
basic CSCW aspect we deal with, focusing on the WYSIWIS (what you see
is what I see) concept and the support of group awareness. Possible architec
tures of groupware systems conclude the chapter. Issues are window sharing,
conferencing components and conference managers, as weIl as collaboration
aware systems.
In Chapter 4 we look into concurrency control concepts. We discuss opti
mistic approaches for concurrency control as weH as approaches with locking,
floor-passing, transactions, and operation transformations. In Chapter 5
we look deeper into replication issues and introduce more sophisticated ap
proaches for concurrency control such as voting and coding schemes as weIl
as the grid protocol. These schemes have the advantage of an enormous im
provement as far as the availability of replicated data is concemed, while
the consistency is guaranteed even during network partitioning. For compar
ison and classification purposes we develop some criteria for evaluating the
possible use of each scheme.
The third part of the book, which contains four chapters, addresses ap
plication classes of computer-supported cooperative work. In Chapter 6 we
deal with communication systems and shared information spaces. The ar-
Preface VII
chitecture and functionality of a typical email system is discussed. Further
attention is directed towards synchronous communication as exemplified by
video conferences. We also present an information management approach to
support the work on shared information in the context of workgroups. We
discuss an architecture for hypermedia systems, the hypertext abstract ma
chine, and t.he Dexter reference model which facilitates the interoperability
between different hypermedia systems. The navigation problem in large in
formation spaces and hypertext-specific solutions are presented. The IBIS
method provides functions to systematicaHy structure the problem solving
information. FinaHy, we present the information space of the Campiello sys
tem, a community support system for tourist applications.
A workflow specifies a set of coordinated activities which represent a 80-
called business process within a company or an organization. In Chapter 7
we deal with workflow management systems, a particular kind of groupware
intended to support. groups of people involved in the execution of business
processes. A workflow management. system coordinates and monit.ors group
act.ivities by handling both causal and temporal interdependencies and the ex
ecution context. After abrief introduction to some basic concepts of workflow
management we discuss the functionality and a possible architecture of work
flow management systems. Various coordination models (e.g., the customer
performer model) are discussed as weH as the conversation model which is
derived from linguistics. Based on the concept of a conversational network
we present the conversation systems Coordinator and Domino, along with
the activity management system Tacts. Besides the standardization activi
ties within the Workflow Management Coalition (WfMC), we discuss adap
tive workflows which handle except.ional situations in flexible ways.
Chapter 8 deals with syst.ems for workgroup computing focusing on the
cooperation between people working in a team. We investigate distributed
document systems and provide an overview of existing group editors. Using
the examples of Iris and DistEdit, we introduce typical problem areas of
group edit.ors. We demonstrate why highly st.ructured documents, along with
logical document views, are advantageous to the handling of joint authoring
scenarios and to the management of shared documents. Concepts for version
and history management. are discussed. Moreover, undo-operations in the
context of group editors are considered in det.ail.
Chapter 9 discusses various aspects of multi agent systems applied for in
telligent coordination of agent-based computer-supported cooperation as re
quired in groupwork. After an initial classification and description of the most
important features of agents, we introduce aspects for modeling distributed
multiagent systems and the cooperation between agents. We explore three
basic approaches for distributed problem solving: the contract net protocol
which is based on the exchange of semistructured messages, an agent-based
information brokerage, and distributed meeting scheduling. Finally, we dis
cuss the actor model by Hewitt.
VIII Preface
Usage of the book. This book is based on two lectures - "Distributed Ap
plications" and "Computer-Supported Cooperative Work" -, regularly held
by J. Schlichter at the Technical University of Munich, Germany, since the
winter of 1991/92, as weH as on the lecture "Distributed Information Manage
ment" held by U. Borghoff at the Technical University of Munich, Germany,
and the University of the Federal Armed Forces Munich, Germany. Between
1985 and 1989 J. Schlichter was a member of the Document Systems Group of
the Xerox Research Center, Webster, NY. Between 1994 and 1998 U. Borghoff
was with the Xerox Research Centre Europe (formerly Rank Xerox Research
Centre) in Grenoble, France. Their work there was quite inftuential to the
content of the book. Furthermore, the results of the five months sabbatical
which J. Schlichter spent at the Xerox Research Centre Europe as weH as
relevant publications by U. Borghoff in the field of agent-based cooperation
have been taken advantage of.
Chapters 1 and 2 may be used as material for a two hour weekly in
troductory lecture on the basics of distributed applications. Should time be
more restricted, Sect. 1.6.5, 1.6.6 and 1.7.4 may be skipped. For a three-hour
weekly lecture on synchronous and asynchronous techniques of distributed
applications, you may wish to use the Chapters 3, 4, 6-9. In case of limited
time, Sect. 3.2, 3.3, 8.3 and 9.6 may be omitted. On first reading of the book
one might skip Chapter 5, since the solutions outlined therein are meant to
enrich special lectures or advanced seminars on the topic of distributed syn
chronization (e.g., distributed operating systems and distributed databases).
Computer-supported cooperative work being a rather newly established
topic within computer science, we cannot provide the reader with references
to advanced textbooks in each chapter. We have, therefore, coHected a rat her
extensive - albeit long - bibliography at the end of the book. The reader
may consult the referenced literature on details of the introduced methods
and concepts.
Acknowledgements. The description of Tacts in Sect. 7.2.6 has been sup
plied by Gunnar Teege. The group editor Iris as introduced in Sect. 8.2.3 has
been implemented as part of several master theses. Our thanks go to Pranz
Bauernfeind, Thorsten Gesing, Michael Koch and Anke Mäkiö, as weH as to
Kathrin Möslein for her preparatory work on the interpretation of the term
CSCW. Our special thanks go to Evelyn Gemkow for typing and translating
parts of the manuscript and always eagerly working away on even roughly
outlined paragraphs. The sketches at the beginning of each chapter were
drawn by Julia Schlichter. We are also most thankful for her careful proof
reading of the entire manuscript. Last but not least, we would like to express
our gratitude towards our publisher Hans Wössner of Springer-Verlag as weH
as towards the reviewer of the first German edition, Christoph Bussler, for
their appreciated comments which have highly contributed to the quality of
the book.
Preface IX
Computer-supported co operation during the production of the
book. The writing of the book itself is a good example for computer
supported cooperative work. The co-authors have dealt with a shared task
(namely the book) while they were both locally distributed (initially, in
France and Germany), and temporally distributed (due to different working
rhythms). It goes without saying that the overall production of the book was
highly cooperative. During several face-to-face sessions the general procedures
were first agreed upon, and later the particulars were repeatedly refined before
being eventually fixed. For information transfer, various means of communi
cation were deployed, ranging from telephone and Fax to email, file transfer
and the world wide web. Sketches of figures for the co-author's opinion were
sent via Fax, whereas email and file transfer constituted the backbone of the
distributed cooperation. Between August and December 1994 alone (work on
the 1st German edition), approximately a thousand emails were sent, partly
with enormous information volume (as in some 130 postscript figures). This
transmission volume was, however, grossly surpassed during the phase of com
plete revision of the book between June 1996 and April 1997. Consolidated
versions of individual chapters were regularly compressed and filed away in
the world wide web where they were offered to the co-author for file trans
fer. The final text processing was performed in Munich where the full and
consistent formatting information was always available. During the work on
this English edition, the authors used the system BSCW (Basic Support for
Cooperative Work) by the German National Research Center for Information
Technology (GMD). The authors have not yet given up hope that a Euro
pean infoffimtion highway will be installed and accessible for some future
cooperation in a form which would allow cooperation methods as offered by
distributed group editors in a better and more efficient way than at present.
Munich, Germany, June 2000 U.M.B.
J.H.S.
