started on intro

mybib.bib

@@ -72,11 +72,18 @@ ISSN={Doi:10.1145/2330667.2330683},}
 
 @BOOK{scsh,
   AUTHOR =       "D. Smith",
-  TITLE =        "Safety Critical Stystems Handbook, 3rd Ed. ISBN 978-0-08-096781-3",
+  TITLE =        "Safety Critical Systems Handbook, 3rd Ed. ISBN 978-0-08-096781-3",
   PUBLISHER =      "Butterworth HeinemannH",
   YEAR =         "2011"
 }
 
+@BOOK{fpodsadsp,
+  AUTHOR =       "Robert D Strum and Donald E. Kirk",
+  TITLE =        "First Principles of discrete Systems and Digital Signal Processing ISBN 0-201-09518-1",
+  PUBLISHER =      "Addison-Wesley",
+  YEAR =         "1988"
+}
+
 @ARTICLE{embedsfmea,
   AUTHOR =       "Peter L. Goddard",
   TITLE =        "Validating The Safety of Embedded Real-Time Control Systems using FMEA",

submission_thesis/CH1_introduction/copy.tex

@@ -30,9 +30,47 @@ firstly looking at electronic circuits and then at electronic/software hybrid sy
 }
 
 \section{Introduction}
+The motivation for this study came form two sources, one academic and the other 
+practical. I had recently completed an
+Msc and my project was to create an Euler/Spider Diagram editor in Java.
+This editor allowed the user to draw Euler/Spider diagrams, and could then 
+represent these as abstract---or mathematical---definitions.
+At work, writing embedded `C' and assembly language code for safety critical
+industrial burners, we were faced with a new and daunting requirement.
+Conformance to the latest European standard, EN298. It appeared to ask for the impossible, 
+not only did it require the usual safety measures (self checking of ROM and RAM, watchdog processors with separate clock sources,  EMC
+triple fail safe control of valves), it had one new clause in it, that had far reaching consequences.
+It stated that in the event of a failure, where the controller had gone into a `lockout~state'--- a state where the controller
+applies all possible safety measures to stop fuel entering the burner---it could not become dangerous should another fault occur.
+In short this meant we had to be able to deal with double failures.
+Any of the components that could, in failing create a dangerous state, were already
+documented and approved using failure mode effects analysis (FMEA). This new requirement
+effectively meant that any all combinations of component failures were
+now required to be analysed. This, from a state explosion problem alone,
+meant that it was going to be virtually impossible to perform.
+%
+Following the concept of de-composing a problem, and thus simplifying the state explosion---using the thinking behind
+the fast Fourier transform (FFT)~\cite{fpodsadsp}[Ch.8], which takes a complex intermeshed series of real and imaginary  number calculations
+and by de-composing them simplifies the problem.
+My reasoning was that were I to analyse the problem in small modules, from the bottom-up following the FFT example, I could apply
+checking for all double failure scenarios.
+Once these first modules were analysed, I now call them {\fgs}, I could determine the symptoms of failure for them
+Using the symptoms of failure, I could now treat these modules as components, now called {\dcs}, and use them to build higher level
+modules. I could apply double simultaneous failure mode checking, because the number of components
+in each module/{\fg} was quite small---thus avoiding state explosion problems, but I could apply
+double checking all the way up the hierarchy. In fact this meant, as a by-product that many multiple as well as double
+failures would be analysed.
 
-Msc project Euler/Spider Diagram editor --- Euler/Spider Diagrams
+
+Euler/Spider Diagrams
 could be used to model failure modes in components.
+Contours could represent failure modes, and the spider diagram 
+`existential~points' instances of failure modes.
+By drawing a spider collecting existential points, a common failure symptom could 
+be determined and from this a new diagram generated automatically, to represent the {\dc}.
+Each spider represented a derived failure mode.
+These concepts were presented at the ``Euler~2004''~\cite{Clark200519} conference at Brighton University.
+
 --- 2005 paper --- need for static analysis because of
 high reliability of modern safety critical systems.