Added text to introduction

introduction/introduction.tex

@@ -2,7 +2,7 @@
 
 \section{Introduction}
 
-$$ \int_{0\-}^{\infty}  f(t).e^{-s.t}.dt  \; | \; s \in C$$
+%$$ \int_{0\-}^{\infty}  f(t).e^{-s.t}.dt  \; | \; s \in C$$
 
 This thesis describes the application of, mathematical (formal) techniques to
 the design of safety critical systems. 
@@ -13,9 +13,53 @@ both the specific `simultaneous failures'\cite{EN298},\cite{EN230},\cite{EN12067
 and the probability to dangerous fault approach\cite{EN61508}.
 
 The visual notation developed was initially designed  for electronic fault modelling.
-However, it could be appleid to mechanical and software domains as well.
-Due to this a common notation/diagram style
-can be used to model any integrated safety relevant system.
+However, it was relaised that could be applied to mechanical and software domains as well.
+This changed the target for the study slightly to encompass these domains in a common notation.
+
+\section{Background}
+
+I completed an MSc in Software engineering in 2004 at Brighton university while working for
+an Engineering firm as a software Engineer. 
+The firm make industrial burner controllers.
+iIndustrial Burners are potentially very dangerous industrail plant.
+They are subject to stringent safety regulations and any product controlling them
+must conform to specific `EN' standards. This involved not only writing software and designing hardware in compliance,
+but also stages of formal certification testing. The certification testing had to be performed by
+`competent body' recognised under European law. A significant part
+of this process was `static testing'. This involved looking at the design of the products,
+from the perspective of components failing, and the effect on safety this would have.
+Some of the static testing involved checking that the germane `EN' standards had
+been complied with. Failure Mode Effects Analysis (FMEA) was also applied. This involved
+looking in detail at critical sections of the product and proposing
+component failure scenarios. For each failure scenario proposed either a satisfactory
+answer was required, or a counter proposal to change the design to cope with
+the comonent failure eventuality. FMEA was time consuming, and being directed by
+experts undoubtly ironed out many potential safety faults before the product saw
+light of day. However it was quickly apparent that only a small proportion
+of copmponent~failure modes was considered. Also  there was no formaliswm.
+The component~failure~modes investigated were not analysed within
+any rigourous framework.
+ 
+\subsection{Possibility of applying mathematical techniques to FMEA}
+
+My MSc project was a diagram editor for Constraint diagrams. 
+I wanted to apply constriant diagram techniques to FMEA
+and began thinking about how this could be done. One 
+obvious factor was that a typical safety critical system could
+have more than 1000 component parts. Each component
+would typically have several failure modes.
+Trying to apply a rigourous methodology on an entire product
+was going to be impractical. To do this with complete coverage
+each component failure mode would have to have been checked against
+the other thousand or so components for influence, and then
+a determination of the effects on the system would have had to have been 
+determined. Thus millions of checks would have to have been performed, and 
+as FMEA is an `expert only' time consuming technique, this idea was 
+obviously impractical.
+
+
+
+
 
 \section{Safety Critical Systems}
 
@@ -23,7 +67,7 @@ can be used to model any integrated safety relevant system.
 
 A safety critical system is one in which lives may depend upon it or 
 it has the potential to become dangerous.
-(/usr/share/texmf-texlive/tex/latex/amsmath/amstext.sty
+(/usr/share/texmf-texlive/tex/latex/amsmath/amstext.sty)
 
 An industrial burner is typical of plant that is potentially dangerous.
 An incorrect air/fuel mixture can be explosive.
@@ -32,11 +76,13 @@ life support are examples of systems that lives depend upon.
 
 \subsection{Two approaches : Probablistic, and Compnent fault tolerant}
 
-There are two main philosophies applied to safety critical systems.
+There are two main philosophies applied to safety critical systems certification.
+\paragraph{Statistical safety Measures}
 One is a general number of acceptable failure per hour of operation.
 This is the probablistic approach and is embodied in the european standard 
 EN61508 \cite{EN61508}.
 
+\paragraph{Prescriptive safety Measures}
 The second philosophy, applied to application specific standards, is to investigate
 components ior sub-systems in the critical safety path and to look at component failure modes
 and ensure that they cannot cause dangerous faults.
@@ -66,14 +112,15 @@ reference chapter dealing speciifically with this but given a quick overview.
 - specific safety standards
 
 \subsubsection{Overview of current testing and certification}
-ref chapter speciiffically on this but give an overview now
+ref chapter speciifically on this but give an overview now
 
 \section{Background to the Industrial Burner Safety Analysis Problem}
 
 An industrial burner is a good example of a safety critical system.
-It has the potential for devatating explosions due to boiler overpressure, or
+It has the potential for devistating explosions due to boiler overpressure, or
 ignition of an explosive mixture, and, because of the large amounts of fuel used,
- is a potential fire hazard. They are often left running unattended 24/7.  
+is also a fire hazard. Also Industrial boilers are often left running unattended 
+for long periods of time (typically days).  
 
 To add to these problems
 Operators are often under pressure to keep them running. An boiler supplying
@@ -86,7 +133,7 @@ This places extra responsibility on the burner controller.
 These are common place and account for a very large proportion of the enery usage
 in the world today (find and ref stats)
 Industrial burners are common enough to have different specific standards
-written for the fuel types they usei \ref{EN298} \ref{EN230} \ref{EN12067}.
+written for the fuel types they use \ref{EN298} \ref{EN230} \ref{EN12067}.
 
 A modern industrial burner has mechanical, electronic and software
 elements, that are all safety critical. That is to say
@@ -374,7 +421,7 @@ and how it will react when it does.
 
 Some systems and components are guaranteed to work within certain environmental constraints,
 temperature being the most typical. Very often what happens to the system outside that range is not defined.
-Where this is the case, these are undetectable errors.
+
 
 
 \section{Project Goals}