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piper/
*.wav
*.ogg
*.onnx*

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Makefile Normal file

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PATH:=./piper:$(PATH)
WAV_FILES := $(patsubst %.txt,%.wav,$(wildcard *.txt))
OGG_FILES := $(patsubst %.txt,%.ogg,$(wildcard *.txt))
MODEL=en_GB-alan-medium.onnx
CONFIG=en_GB-alan-medium.onnx.json
complete: $(OGG_FILES)
echo $@ $^
$(WAV_FILES): %.wav: %.txt
cat $^ | piper -m $(MODEL) -c $(CONFIG) -f $@
$(OGG_FILES): %.ogg: %.wav
ffmpeg -i $^ $@
install:
wget -O piper.tar "https://github.com/rhasspy/piper/releases/download/v1.2.0/piper_amd64.tar.gz"
tar xf piper.tar
wget -O en_GB-alan-medium.onnx "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/alan/medium/en_GB-alan-medium.onnx?download=true"
wget -O en_GB-alan-medium.onnx.json "https://huggingface.co/rhasspy/piper-voices/resolve/v1.0.0/en/en_GB/alan/medium/en_GB-alan-medium.onnx.json?download=true.json"

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chapter 1.
Why Do We Need Something Different?
This book presents a new approach to building safer systems that departs in impor-
tant ways from traditional safety engineering. While the traditional approaches
worked well for the simpler systems of the past for which they were devised, signifi-
cant changes have occurred in the types of systems we are attempting to build today
and the context in which they are being built. These changes are stretching the limits
of safety engineering..
point one.
•Fast pace of technological change. Although learning from past accidents is
still an important part of safety engineering, lessons learned over centuries
about designing to prevent accidents may be lost or become ineffective
when older technologies are replaced with new ones. Technology is changing
much faster than our engineering techniques are responding to these changes.
New technology introduces unknowns into our systems and creates new paths
to losses..
point two.
•Reduced ability to learn from experience. At the same time that the develop-
ment of new technology has sprinted forward, the time to market for new
products has greatly decreased, and strong pressures exist to decrease this
time even further. The average time to translate a basic technical discovery into
a commercial product in the early part of this century was thirty years. Today
our technologies get to market in two to three years and may be obsolete in
five. We no longer have the luxury of carefully testing systems and designs
to understand all the potential behaviors and risks before commercial or
scientific use..
point three.
•Changing nature of accidents. As our technology and society change, so do
the causes of accidents. System engineering and system safety engineering
techniques have not kept up with the rapid pace of technological innovation.
Digital technology, in particular, has created a quiet revolution in most fields
of engineering. Many of the approaches to prevent accidents that worked on
electromechanical components—such as replication of components to protect
against individual component failure—are ineffective in controlling accidents
that arise from the use of digital systems and software..
point four.
•New types of hazards. Advances in science and societal changes have created
new hazards. For example, the public is increasingly being exposed to new man-
made chemicals or toxins in our food and our environment. Large numbers of
people may be harmed by unknown side effects of pharmaceutical products.
Misuse or overuse of antibiotics has given rise to resistant microbes. The most
common safety engineering strategies have limited impact on many of these
new hazards.
point five.
•Increasing complexity and coupling. Complexity comes in many forms, most
of which are increasing in the systems we are building. Examples include
interactive complexity (related to interaction among system components),
dynamic complexity (related to changes over time), decompositional complex-
ity (where the structural decomposition is not consistent with the functional
decomposition), and nonlinear complexity (where cause and effect are not
related in a direct or obvious way). The operation of some systems is so
complex that it defies the understanding of all but a few experts, and some-
times even they have incomplete information about the system’s potential
behavior. The problem is that we are attempting to build systems that are
beyond our ability to intellectually manage; increased complexity of all types
makes it difficult for the designers to consider all the potential system states
or for operators to handle all normal and abnormal situations and distur-
bances safely and effectively. In fact, complexity can be defined as intellectual
unmanageability.
This situation is not new. Throughout history, inventions and new technology
have often gotten ahead of their scientific underpinnings and engineering
knowledge, but the result has always been increased risk and accidents until
science and engineering caught up.1 We are now in the position of having
to catch up with our technological advances by greatly increasing the power
of current approaches to controlling risk and creating new improved risk
management strategies.
Footnote to point five.
As an example, consider the introduction of high-pressure steam engines in the first half of the nine-
teenth century, which transformed industry and transportation but resulted in frequent and disastrous
explosions. While engineers quickly amassed scientific information about thermodynamics, the action of
steam in the cylinder, the strength of materials in the engine, and many other aspects of steam engine
operation, there was little scientific understanding about the buildup of steam pressure in the boiler, the
effect of corrosion and decay, and the causes of boiler explosions. High-pressure steam had made the
current boiler design obsolete by producing excessive strain on the boilers and exposing weaknesses in
the materials and construction. Attempts to add technological safety devices were unsuccessful because
engineers did not fully understand what went on in steam boilers. It was not until well after the middle
of the century that the dynamics of steam generation was understood.
point six.
•Decreasing tolerance for single accidents. The losses stemming from acci-
dents are increasing with the cost and potential destructiveness of the systems
we build. New scientific and technological discoveries have not only created
new or increased hazards (such as radiation exposure and chemical pollution)
but have also provided the means to harm increasing numbers of people as the
scale of our systems increases and to impact future generations through envi-
ronmental pollution and genetic damage. Financial losses and lost potential
for scientific advances are also increasing in an age where, for example, a space-
craft may take ten years and up to a billion dollars to build, but only a few
minutes to lose. Financial system meltdowns can affect the world’s economy
in our increasingly connected and interdependent global economy. Learning
from accidents or major losses (the fly-fix-fly approach to safety) needs to be
supplemented with increasing emphasis on preventing the first one.
point seven
•Difficulty in selecting priorities and making tradeoffs. At the same time that
potential losses from single accidents are increasing, companies are coping with
aggressive and competitive environments in which cost and productivity play
a major role in short-term decision making. Government agencies must cope
with budget limitations in an age of increasingly expensive technology. Pres-
sures are great to take shortcuts and to place higher priority on cost and sched-
ule risks than on safety. Decision makers need the information required to
make these tough decisions.
point eight.
•More complex relationships between humans and automation. Humans
are increasingly sharing control of systems with automation and moving into
positions of higher-level decision making with automation implementing the
decisions. These changes are leading to new types of human error—such as
various types of mode confusion—and a new distribution of human errors, for
example, increasing errors of omission versus commission. Inade-
quate communication between humans and machines is becoming an increas-
ingly important factor in accidents. Current approaches to safety engineering
are unable to deal with these new types of errors.
All human behavior is influenced by the context in which it occurs, and
operators in high-tech systems are often at the mercy of the design of the auto-
mation they use or the social and organizational environment in which they
work. Many recent accidents that have been blamed on operator error could
more accurately be labeled as resulting from flaws in the environment in which
they operate. New approaches to reducing accidents through improved design
of the workplace and of automation are long overdue.
point nine.
•Changing regulatory and public views of safety. In today’s complex and
interrelated societal structure, responsibility for safety is shifting from the
individual to government. Individuals no longer have the ability to control the
risks around them and are demanding that government assume greater respon-
sibility for ensuring public safety through laws and various forms of oversight
and regulation as companies struggle to balance safety risks with pressure to
satisfy time-to-market and budgetary pressures. Ways to design more effective
regulatory strategies without impeding economic goals are needed. The alter-
native is for individuals and groups to turn to the courts for protection, which
has many potential downsides, such as stifling innovation through fear of law-
suits as well as unnecessarily increasing costs and decreasing access to products
and services.
end of points.
Incremental improvements in traditional safety engineering approaches over
time have not resulted in significant improvement in our ability to engineer safer
systems. A paradigm change is needed in the way we engineer and operate the types
of systems and hazards we are dealing with today. This book shows how systems
theory and systems thinking can be used to extend our understanding of accident
causation and provide more powerful (and surprisingly less costly) new accident
analysis and prevention techniques. It also allows a broader definition of safety and
accidents that go beyond human death and injury and includes all types of major
losses including equipment, mission, financial, and information.
Part I of this book presents the foundation for the new approach. The first step
is to question the current assumptions and oversimplifications about the cause of
accidents that no longer fit today’s systems (if they ever did) and create new assump-
tions to guide future progress. The new, more realistic assumptions are used to create
goals to reach for and criteria against which new approaches can be judged. Finally,
the scientific and engineering foundations for a new approach are outlined.
Part II presents a new, more inclusive model of causality, followed by part III,
which describes how to take advantage of the expanded accident causality model
to better manage safety in the twenty-first century.

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ENGINEERING A SAFER WORLD.
Systems Thinking Applied to Safety.
By Nancy G Leveson.
The MIT Press.
Cambridge, Massachusetts.
London, England.
We pretend that technology, our technology, is something of a life force, a will, and a thrust
of its own, on which we can blame all, with which we can explain all, and in the end by
means of which we can excuse ourselves.
—T Cuyler Young, Man in Nature.
Series Foreword.
Engineering Systems is an emerging field that is at the intersection of engineering,
management, and the social sciences. Designing complex technological systems
requires not only traditional engineering skills but also knowledge of public policy
issues and awareness of societal norms and preferences. In order to meet the
challenges of rapid technological change and of scaling systems in size, scope, and
complexity, Engineering Systems promotes the development of new approaches,
frameworks, and theories to analyze, design, deploy, and manage these systems.
This new academic field seeks to expand the set of problems addressed by engi-
neers, and draws on work in the following fields as well as others.
one.• Technology and Policy.
two.• Systems Engineering.
three.• System and Decision Analysis, Operations Research.
four.• Engineering Management, Innovation, Entrepreneurship.
five.• Manufacturing, Product Development, Industrial Engineering.
The Engineering Systems Series will reflect the dynamism of this emerging field
and is intended to provide a unique and effective venue for publication of textbooks
and scholarly works that push forward research and education in Engineering
Systems.
Preface.
I began my adventure in system safety after completing graduate studies in com-
puter science and joining the faculty of a computer science department. In the first
week at my new job, I received a phone call from Marion Moon, a system safety
engineer at what was then the Ground Systems Division of Hughes Aircraft
Company. Apparently he had been passed between several faculty members, and I
was his last hope. He told me about a new problem they were struggling with on a
torpedo project, something he called. “software safety.” I told him I didn ot know
anything about it and that I worked in a completely unrelated field. I added that I
was willing to look into the problem. That began what has been a thirty-year search
for a solution and to the more general question of how to build safer systems.
Around the year 2000, I became very discouraged. Although many bright people
had been working on the problem of safety for a long time, progress seemed to be
stalled. Engineers were diligently performing safety analyses that did not seem to
have much impact on accidents. The reason for the lack of progress, I decided, was
that the technical foundations and assumptions on which traditional safety engineer-
ing efforts are based are inadequate for the complex systems we are building today.
The world of engineering has experienced a technological revolution, while the
basic engineering techniques applied in safety and reliability engineering, such as
fault tree analysis (FTA) and failure modes and effects analysis (FMEA), have
changed very little. Few systems are built without digital components, which operate
very differently than the purely analog systems they replace. At the same time, the
complexity of our systems and the world in which they operate has also increased
enormously. The old safety engineering techniques, which were based on a much
simpler, analog world, are diminishing in their effectiveness as the cause of
accidents changes.
For twenty years I watched engineers in industry struggling to apply the old
techniques to new software-intensive systems — expending much energy and having
little success. At the same time, engineers can no longer focus only on technical
issues and ignore the social, managerial, and even political factors that impact safety
if we are to significantly reduce losses. I decided to search for something new. This
book describes the results of that search and the new model of accident causation
and system safety techniques that resulted.
The solution, I believe, lies in creating approaches to safety based on modern
systems thinking and systems theory. While these approaches may seem new or
paradigm changing, they are rooted in system engineering ideas developed after
World War 2. They also build on the unique approach to engineering for safety,
called System Safety, that was pioneered in the 1950s by aerospace engineers such
as C O Miller, Jerome Lederer, and Willie Hammer, among others. This systems
approach to safety was created originally to cope with the increased level of com-
plexity in aerospace systems, particularly military aircraft and ballistic missile
systems. Many of these ideas have been lost over the years or have been displaced
by the influence of more mainstream engineering practices, particularly reliability
engineering.
This book returns to these early ideas and updates them for todays technology.
It also builds on the pioneering work in Europe of Jens Rasmussen and his followers
in applying systems thinking to safety and human factors engineering.
Our experience to date is that the new approach described in this book is more
effective, less expensive, and easier to use than current techniques. I hope you find
it useful.
Relationship to Safeware.
My first book, Safeware, presents a broad overview of what is known and practiced
in System Safety today and provides a reference for understanding the state of the
art. To avoid redundancy, information about basic concepts in safety engineering
that appear in Safeware is not, in general, repeated. To make this book coherent
in itself, however, there is some repetition, particularly on topics for which my
understanding has advanced since writing Safeware.
Audience.
This book is written for the sophisticated practitioner rather than the academic
researcher or the general public. Therefore, although references are provided, an
attempt is not made to cite or describe everything ever written on the topics or to
provide a scholarly analysis of the state of research in this area. The goal is to provide
engineers and others concerned about safety with some tools they can use when
attempting to reduce accidents and make systems and sophisticated products safer.
It is also written for those who are not safety engineers and those who are
not even engineers. The approach described can be applied to any complex,
sociotechnical system such as health care and even finance. This book shows you
how to “reengineer” your system to improve safety and better manage risk. If pre-
venting potential losses in your field is important, then the answer to your problems
may lie in this book.
Contents.
The basic premise underlying this new approach to safety is that traditional models
of causality need to be extended to handle todays engineered systems. The most
common accident causality models assume that accidents are caused by component
failure and that making system components highly reliable or planning for their
failure will prevent accidents. While this assumption is true in the relatively simple
electromechanical systems of the past, it is no longer true for the types of complex
sociotechnical systems we are building today. A new, extended model of accident
causation is needed to underlie more effective engineering approaches to improving
safety and better managing risk.
The book is divided into three sections. The first part explains why a new approach
is needed, including the limitations of traditional accident models, the goals for a
new model, and the fundamental ideas in system theory upon which the new model
is based. The second part presents the new, extended causality model. The final part
shows how the new model can be used to create new techniques for system safety
engineering, including accident investigation and analysis, hazard analysis, design
for safety, operations, and management.
This book has been a long time in preparation because I wanted to try the new
techniques myself on real systems to make sure they work and are effective. In
order not to delay publication further, I will create exercises, more examples, and
other teaching and learning aids and provide them for download from a website in
the future.
Chapters 6 – 10, on system safety engineering and hazard analysis, are purposely
written to be stand-alone and therefore usable in undergraduate and graduate
system engineering classes where safety is just one part of the class contents and
the practical design aspects of safety are the most relevant.
Acknowledgments.
The research that resulted in this book was partially supported by numerous research
grants over many years from NSF and NASA. David Eckhardt at the NASA Langley
Research Center provided the early funding that got this work started.
I also am indebted to all my students and colleagues who have helped develop
these ideas over the years. There are too many to list, but I have tried to give them
credit throughout the book for the ideas they came up with or we worked on
together. I apologize in advance if I have inadvertently not given credit where it is
due. My students, colleagues, and I engage in frequent discussions and sharing of
ideas, and it is sometimes difficult to determine where the ideas originated. Usually
the creation involves a process where we each build on what the other has done.
Determining who is responsible for what becomes impossible. Needless to say, they
provided invaluable input and contributed greatly to my thinking.
I am particularly indebted to the students who were at MIT while I was writing
this book and played an important role in developing the ideas: Nicolas Dulac,
Margaret Stringfellow, Brandon Owens, Matthieu Couturier, and John Thomas.
Several of them assisted with the examples used in this book.
Other former students who provided important input to the ideas in this book
are Matt Jaffe, Elwin Ong, Natasha Neogi, Karen Marais, Kathryn Weiss, David
Zipkin, Stephen Friedenthal, Michael Moore, Mirna Daouk, John Stealey, Stephanie
Chiesi, Brian Wong, Mal Atherton, Shuichiro Daniel Ota, and Polly Allen.
Colleagues who provided assistance and input include Sidney Dekker, John
Carroll, Joel Cutcher-Gershenfeld, Joseph Sussman, Betty Barrett, Ed Bachelder,
Margaret-Anne Storey, Meghan Dierks, and Stan Finkelstein.

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HMO H M O
MIC M I C
DC-10 D C 10.