Add slides on the distinction between operational and descriptive specification

Lectures/L16_MISContinued/MISContinued.tex

@@ -1108,6 +1108,65 @@ $ms$: real
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+\begin{frame}
+\frametitle{Classification of Specification Styles}
+
+\begin{itemize}
+
+\item Informal, semi-formal, formal
+\item Operational
+\begin{itemize}
+\item Behaviour specification in terms of some abstract machine
+\item Not specifying how to implement, even though it looks this way
+\end{itemize}
+\item Descriptive
+\begin{itemize}
+\item Behaviour described in terms of properties
+\item Prefer this because if its inherent abstraction
+\end{itemize}
+\item The module state machine specification that we use is a mix of operational
+  and descriptive specification - \structure{Why?}
+
+\end{itemize}
+
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\begin{frame}
+\frametitle{Example Operational Specification}
+
+\begin{itemize}
+
+\item Specification of a geometric figure $E$
+\item $E$ can be drawn as follows
+\begin{enumerate}
+\item Select two points $P_1$ and $P_2$ on a plane
+\item Get a string of a certain length and fix its ends to $P_1$ and $P_2$
+\item Position a pencil as shown in the next figure
+\item Move the pen clockwise, keeping the string tightly stretched,  until you reach the point where you started
+drawing
+\end{enumerate}
+\end{itemize}
+\begin{figure}
+\includegraphics[scale=0.35]{DrawingACircle.png}
+\end{figure}
+
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\begin{frame}
+\frametitle{Example Descriptive Specification}
+
+Geometric figure $E$ is described by the following equation
+$$ a x^2 + b y^2 + c = 0 $$
+where $a$, $b$ and $c$ are suitable constants
+
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 \begin{frame}
 \frametitle{Judging Appropriate Abstraction}
 
@@ -1125,9 +1184,11 @@ $ms$: real
 \bi
 \item If a change in how your code works requires a change in your
   specification, look for a better abstraction
-\item If writing and maintaining the spec is exceedingly frustrating, the spe
+\item If writing and maintaining the spec is exceedingly frustrating, the spec
   could be too concrete
 \ei
+\item The goal is to provide a descriptive, formal mathematical spec of
+  eveything, but at times we sacrifice this goal in the name of practicality
 \end{itemize}
 
 \end{frame}