removed all refs to parts~list

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submission_thesis/CH4_FMMD/copy.tex

@@ -56,7 +56,7 @@ starts with %an overview of current failure modelling techniques, and then
 a worked example using the new methodology, 
 Failure Mode Modular De-composition (FMMD).
 This is followed by a discussion on the design of the FMMD methodology and then
-an ontological description is given using UML class models.
+an ontological description using UML class models.
 %A  notation is then described to index and classify objects created in FMMD hierarchical models.
 
 
@@ -648,7 +648,7 @@ We then represent the {\dc} as a DAG in figure  \ref{fig:dc1dag}.
 % We now have a {\dc} model for a generic potential divider, and can use it
 % as a building block for other {\fgs} in the same way as we used the base components $R1$ and $R2$.
 
-\clearpage
+%\clearpage
 
 %\paragraph{Failure Mode Analysis of the OP-AMP}
 
@@ -691,7 +691,7 @@ We can represent these failure modes on a DAG (see figure~\ref{fig:op1dag}).
 %}
 %{
 %}
-\clearpage
+%\clearpage
 %\paragraph{Modelling the OP amp with the potential divider.}
 We now merge the OP amp and the {\dc} $PD$, to
 form a {\fg} to represent the non inverting amplifier.
@@ -872,7 +872,7 @@ and this is represented in table \ref{tbl:ampfmea1}.
 
 For this amplifier configuration we have three failure modes; $AMPHigh, AMPLow, LowPass$.%see figure~\ref{fig:fgampb}.
 This model now has two stages of analysis hierarchy, as represented in figure~\ref{fig:dc2}.
-From the analysis in table \ref{tbl:ampfmea1} we can create the {\dc} $INVAMP$ which 
+From the analysis in table \ref{tbl:ampfmea1} we can create the {\dc} $INVAMP$, which 
 represents the failure mode behaviour of the non-inverting amplifier.
 
 \begin{figure}[h]
@@ -886,7 +886,7 @@ represents the failure mode behaviour of the non-inverting amplifier.
 We can now examine the {\dc} $INVAMP$ by drawing it as a DAG.
 %expand the $PD$ {\dc} and  have a full FMMD failure %mode 
 %model
-We can traverse this DAG, and thus determine all possible causes to
+We can traverse this DAG, and thus determine all possible causes for
 the three high level symptoms, i.e. the failure~modes of the non-inverting amplifier $INVAMP$.
 %
 Figure \ref{fig:noninvdag1} shows a fully expanded DAG, from which we can derive information
@@ -943,14 +943,14 @@ System & A product designed to
 
  
 
-Base Component & An atomic building block used at the lowest level of the FMMD model
+Base Component & An atomic building block used at the lowest level of an FMMD model
                  \footnote{In the case of combinatorial packaged parts (such as a chip containing
                  four op-amps, each op-amp on the chip is considered as one atomic, or {\em{\bc}}).}.
        \\
 {\em Constraint} & This object must have a defined set of failure~modes. \\    \hline 
 
 
-Component  & A building block, this may be a part from a parts list or a sub-assembly. \\  
+Component  & A building block, this may be a {\bc} or a sub-assembly. \\  
 {\em Constraint} & This object must have a defined set of failure~modes. \\    \hline 
 
 
@@ -1009,7 +1009,7 @@ Here we have four op-amps on one chip. For FMEA we would consider each op-amp in
 as a separate building block for a circuit.
 %
 We, in fact, need to go a little further than the above definition of a part, 
-and say that we want to define an atomic entity used as a building block.
+and say that we want to define an atomic entity. % used as a building block.
 %The term component, in American English, can mean a building block or a part.
 %In British-English a component generally is given to mean the definition for part above.
 We define {\bc} to be the lowest level of component that we use as a building block.
@@ -1017,11 +1017,12 @@ This is a choice made by the analyst.
 %
 Both op-amps and transistors have published statistical failure rates and yet an op-amp is made out of transistors.
 %
-A circuit designer would consider individual transistors and individual op-amps
+However, a  circuit designer would usually consider individual transistors and individual op-amps
 as lowest level building blocks.
+%
 In fact any component with published failure modes could be considered to be a {\bc},
 but this determination is the choice of the analyst or the guidelines of the 
-standard~\cite{en298}~\cite{en61508}~\cite{en230} to which we are approving the product to.
+standard~\cite{en298}~\cite{en61508}~\cite{en230} to which we are approving/analysing a system.
 
 %a lowest level of assembly `part' or an atomic entity, which ever is the smaller
 %and component to mean either a part or a sub-assembly. 
@@ -1051,7 +1052,7 @@ CD-player, tuner, amplifier~separate, loudspeakers and ipod~interface.
 %and is the way in which FTA\cite{nucfta} analyses a System
 %and breaks it down.
 \paragraph{  {\fgs} and components.}
-A components will be composed of `components', recursively down to
+Components can be composed of `components', recursively down to
 the {\bcs}. 
 %
 However each `component'
@@ -1059,17 +1060,16 @@ will have a fault/failure behaviour and it should
 always be possible to obtain a set of failure modes
 for each `component'.  
 %In FMMD terms a sub-system is a derived component.
-
+%
 If we look at the sound system example, 
 the CD~player could fail in several distinct ways, 
 and this could  have been caused by a number of {\textbf{the CD players internal}} component failure modes.
 %no matter what has happened to it or has gone wrong inside it.
-
-
+%
 Using the reasoning that working from the bottom up forces the consideration of all possible
 component failures (which can be missed in a top~down approach \cite{faa}[Ch.9])
 we are presented with a problem. Which initial collections of base components should we choose?
-
+%
 For instance in the CD~player example; if we start at the bottom, we are presented with
 a massive list of base~components, resistors, motors, user~switches, laser~diodes, all sorts! 
 Clearly, working from the bottom~up, we need to pick small
@@ -1085,10 +1085,10 @@ as one of the base level {\fgs}.
 %for the smallest `functional~groups' of components within a system. 
 We can define a {\fg} as a set of components that interact
 to perform a specific function.
-
+%
 When we have analysed the fault behaviour of a {\fg}, we can treat it as a `black box'.
 %
-The fault behaviour will consist of a set of `symptoms' caused by combinations
+The {\fgs} fault behaviour will consist of a set of `symptoms' caused by combinations
 of its component failure modes.
 %
 We can thus make a new `component' derived from the symptoms found as a result of analysing the {\fg}.
@@ -1175,24 +1175,26 @@ each failure mode is referenced back to only one component. This constraint is d
 %%-%% The lower resistance part will draw more current and therefore have a statistically higher chance of failure.}.
 
 
-Controlled products are typically built using a large number of components and these are traditionally
-kept in a `parts~list'. 
+%Controlled products are typically built using a large number of components and these are traditionally
+%kept in a `parts~list'. 
 %
 For a safety critical product this is usually a formal document 
 and is used for ordering systems from third parties, and by quality inspectors 
 to ensure the correct parts are being fitted.
 %The parts list is shown for completeness here, as people involved with Printed Circuit Board (PCB) and electronics production, verification and testing would want to know where it lies in the model.
-The parts list is not actively used in the FMMD method, but is shown in the UML model for completeness.
-For the UML diagram in figure \ref{fig:componentpl} the parts list is simply a collection of components.
-\begin{figure}[h]
- \centering
- \includegraphics[width=400pt,bb=0 0 712 68,keepaspectratio=true]{CH4_FMMD/componentpl.png}
- % componentpl.png: 712x68 pixel, 72dpi, 25.12x2.40 cm, bb=0 0 712 68
- \caption{Parts List of Components}
- \label{fig:componentpl}
-\end{figure}
-
-%Components in the parts list % (bought in parts) 
+%The parts list is not actively used in the FMMD method, but is shown in the UML model for completeness.
+%
+%For the UML diagram in figure \ref{fig:componentpl} the parts list is simply a collection of components.
+%
+% \begin{figure}[h]
+%  \centering
+%  \includegraphics[width=400pt,bb=0 0 712 68,keepaspectratio=true]{CH4_FMMD/componentpl.png}
+%  % componentpl.png: 712x68 pixel, 72dpi, 25.12x2.40 cm, bb=0 0 712 68
+%  \caption{Parts List of Components}
+%  \label{fig:componentpl}
+% \end{figure}
+% 
+% %Components in the parts list % (bought in parts) 
 %will be termed `base~components'.
 %Components derived from base~components (i.e. sub-assemblies) will not always require 
 %parts~numbers\footnote{It is common practise for sub-assemblies, PCB's, mechanical parts,
@@ -1203,15 +1205,17 @@ For the UML diagram in figure \ref{fig:componentpl} the parts list is simply a c
 %not require a vendor reference, but must be named locally in the FMMD model.
 
 We can term `modularising a system', to mean recursively breaking it into smaller sections for analysis.
+%
 When modularising a system from the top~down, as in Fault Tree Analysis (FTA)~\cite{nasafta}\cite{nucfta} ,
 it is common to term the modules identified as sub-systems.
+%
 When modularising failure mode behaviour from the bottom up, it is more meaningful to call them `derived~components'.
  
 
 
 \section{Failure Modes in depth}
 
-For FMEA appraisals of systems we begin with {\bcs}. 
+FMEA appraisals of systems we begin with {\bcs}~\cite{en298}~\cite{bfmea}~\cite{en61508}. 
 %These will have a set of failure modes assigned to them.
 In order to perform FMEA we require a set of failure modes for each {\bc} in the system under investigation.
 %
@@ -1226,6 +1230,7 @@ With these symptoms, we can trace their effects through the system under investi
 and determine outcomes.
 %
 Different approval agencies may list different failure mode sets for the same generic components.
+%
 This apparent anomaly is discussed in section~\ref{sec:determine_fms} using two common electronic components
 as examples.
 
@@ -1244,27 +1249,35 @@ as examples.
 
 Traditional static fault analysis methods work from the top down.
 They identify faults that can occur in a system, and then work down
-to see how they could be caused. Some apply statistical techniques to
+to see how they could be caused. 
+%
+Some apply statistical techniques to
 determine the likelihood of component failures 
-causing specific system level errors. For example the FMEA variant FMECA, uses
+causing specific system level errors. 
+%
+For example the FMEA variant FMECA, uses
 Bayes theorem~\cite{probstat}[p.170]~\cite{nucfta}[p.74] (the relation between a conditional probability and its reverse)
 and is  applied to specific failure modes in components and their probability of causing given system level errors.
 Another top down methodology is to apply cost benefit analysis 
 to determine which faults are the highest priority to fix~\cite{bfmea}.
+%
 The aim of FMMD analysis is to produce complete  failure
 models of safety critical systems  from the bottom-up,
 starting, where possible with known base~component failure~modes.
 
 An advantage of working from the bottom up is that we can ensure that
-all component failure modes must be considered. A top down approach
+all component failure modes must be considered. 
+%
+A top down approach
 can miss individual failure modes of components~\cite{faa}[Ch.~9],
 especially where there are non-obvious top-level faults.
 
 \subsection{FMMD Process in outline.}
 
 In order to analyse from the bottom-up, we need to take
-small groups of components from the parts~list that naturally
+small groups of components that naturally
 work together to perform a simple function.
+%
 The components to include in a  {\fg} are chosen by hand.
 %a human, the analyst.
 %We can represent the `Functional~Group' as a class. 
@@ -1272,6 +1285,8 @@ The components to include in a  {\fg} are chosen by hand.
 `{\fg}' we can look at the components it contains,
 and from this determine the failure modes of all the components that belong to it.
 %
+Initial {\fgs} will consist of {\bcs}.
+%
 % and determine a failure mode model for that group.
 %
 % expand 21sep2010
@@ -1280,18 +1295,26 @@ and from this determine the failure modes of all the components that belong to i
 %can fail. 
 %
 All the failure modes of all the components within a {\fg} are collected.
+%
 As each component mode holds a set of failure modes, the {\fg} represents a set of sets of failure modes.
+%
 We convert this 
 into a flat set 
 of failure modes for use in analysis.
+%
 A flat set is a set containing just failure modes and not sets of failure modes~\cite{joyofsets}[p.8].
 %
+%In practical term each component failure mode is considered as a `failure~scenario' or 'test~case'
+%for the {\fg}.
+%
 Each of these failure modes, and optionally combinations of them, are
-formed into `test cases' which are
+formed into `test~cases' which are
 analysed for their effect on the failure mode behaviour of the `{\fg}'.
 %
-Once we have the failure mode behaviour of the {\fg}, we can determine a new set of failure modes, the derived failure modes of the
-`{\fg}'.
+Once we have the failure mode behaviour of the {\fg}, we can determine a the symptoms of failure
+for the {\fg}.
+%
+We could term these symptoms the derived failure modes of the `{\fg}'.
 % 
 Or in other words we can determine how the `{\fg}' can fail.
 We can now consider the {\fg} as a sort of super component
@@ -1303,21 +1326,18 @@ with its own set of failure modes.
 The process for taking a {\fg}, analysing its failure mode behaviour considering
 all the failure modes of all the components in the group,
 and collecting symptoms of failure,  is termed `symptom abstraction'.
-\ifthenelse {\boolean{paper}}
-{
-}
-{
+%
 This 
 is dealt with in detail using an algorithmic description, in section \ref{sec:algorithmfmmd}.
-}
+
 
 % define difference between a \fg and a \dc
 A {\fg} is a collection of components, a {\dc} is a new `theoretical'
 component which has a set of failure modes,
 corresponding to the failure symptoms from the {\fg} from which it was derived.
 %
-We   consider a {\dc} as a black box, or component 
-for use.
+We now  consider a {\dc} as a black box, or component 
+for use in further levels of analysis.
 %, and in this case it would have a set of failure modes.
 %Looking at the {\fg} in this way is seeing it as a {\dc}.
 
@@ -1329,7 +1349,7 @@ and creates a new {\dc} from it.
 %must consider all the failure modes of the components in the functional
 %group.
 The newly created {\dc} requires a set of failure modes of its own.
-These failure modes are the failure mode behaviour of the {\fg} from which it was derived.
+These failure modes are the failure mode behaviour---or symptoms---of the {\fg} from which it was derived.
 %
 Because these new failure modes were derived from a {\fg}, we can call 
 these `derived~failure~modes'.
@@ -1337,7 +1357,7 @@ these `derived~failure~modes'.
 We thus have a `new' component, or system building block, but with a known and traceable
 fault behaviour.
 
-The UML representation  (in figure \ref{fig:cfg}) shows a `functional group' having a one to one relationship with a derived~component.
+The UML representation  (in figure \ref{fig:cfg}) shows a `{\fg}' having a one to one relationship with a derived~component.
 
 The symbol $\derivec$ is used to indicate the analysis process that takes a
 functional group and converts it into a new component.
@@ -1385,6 +1405,7 @@ We may now use the  $INVAMP$ {\dc} in even higher level {\fgs}.
 \label{sec:alpha}
 The UML meta model in figure \ref{fig:cfg}, shows the relationships
 between the entities used in FMMD.
+%
 Note that because we can use derived components to build functional groups,
 this model intrinsically supports % building a 
 hierarchy.
@@ -1404,7 +1425,7 @@ have a `level' of $\abslev=0$.
 % I do not know how to make this simpler
 Derived~components take a level based on the highest level
 component used to build the functional group it was derived from plus 1.
-So a derived component built from base level or parts list components
+So a derived component built from base level components
 would have an $\abslev$ value of 1.
 %\clearpage
 
@@ -1440,14 +1461,17 @@ and can now complete the picture.
 For the complete UML data model we need to consider the System
 as a data structure. 
 
-The `parts~list' is the 
-key reference point and starting point. % in the data structure.
-Our base components are kept here.
-From these the initial {\fgs} are formed, and from the first {\fgs},
-the first {\dcs}. Two other data types/entities are required 
+%The `parts~list' is the 
+%key reference point and starting point. % in the data structure.
+%Our base components are kept here.
+
+From the {\bcs} the initial {\fgs} are formed, and from the first {\fgs},
+the first {\dcs}. 
+%
+Two other data types/entities are required 
 however: we need to model environmental and operational states and
 where they fit into the data structure.
-
+%
 A  system will be expected to perform in a given environment.
 %
 Environment in the context of this study
@@ -1458,11 +1482,11 @@ a working temperature range, for instance.
 Mechanical components could  be specified for stress and loading limits.
 
 
-Systems or sub-systems may have distinct operational states. For instance, a safety critical controller
+Systems may have distinct operational states. For instance, a safety critical controller
 may have a LOCKOUT state where it has detected a serious problem and will not continue to operate until 
 authorised human intervention takes place.
-A safety critical circuit may have a self test mode.
-
+A safety critical circuit may have a self test mode which could be operated externally.
+%
 Operational states and environmental conditions must be factored into the UML model.
 
 \paragraph{Environmental Modelling.} The external influences/environment could typically be temperature ranges,
@@ -1470,7 +1494,7 @@ levels of electrical interference, high voltage contamination on supply
 lines, radiation levels etc.
 Environmental influences will affect specific components in specific ways.\footnote{A good example of a part 
 affected by environmental conditions, in this case temperature, is the opto-isolator~\cite{tlp181}
-which is typically affected at around \oc{60}. Most electrical components are far more robust to temperature.}.
+which is typically affected at around {60 \oc}. Most electrical components are more robust to temperature variations.}.
 Environmental analysis is thus applicable to components.
 Environmental influences, such as over stress due to voltage
 can be eliminated by down-rating of components as discussed in section~\ref{sec:determine_fms}.
@@ -1479,10 +1503,10 @@ With given environmental constraints, we can therefore eliminate some failure mo
 
 \paragraph{Operational states.}
 Within the field of safety critical engineering, we often encounter 
-sub-systems that include test or self-test facilities. 
+elements that include test or self-test facilities. 
 %
 We also encounter degraded performance
-(such as only performing functions in an emergency) and lockout conditions.
+(such as only performing functions in an emergency) and lockout/emergency conditions.
 These can be broadly termed operational states. %, and apply to the 
 %functional groups.
 %
@@ -1494,10 +1518,9 @@ When the TEST line is activated, it supplies a test signal
 which will validate the circuit. This circuit will have two operational states,
 NORMAL and TEST mode.
 %
-It seems better to apply the operational states to functional groups.
+It seems better to apply the operational states to {\fgs}.
 %
-Functional groups by definition implement functionality, or purpose
-of particular sub-systems, and therefore are the best objects to model
+Functional groupings by definition implement functionality, or purpose, and therefore are the best objects to model
 operational states.% with.
 
 \paragraph{Inhibit Conditions.}