diff -r 5751a3ee41ce -r 89588d84998d hw01.tex
--- a/hw01.tex	Thu Sep 27 12:02:45 2012 +0100
+++ b/hw01.tex	Thu Sep 27 12:22:08 2012 +0100
@@ -1,41 +1,35 @@
 \documentclass{article}
 \usepackage{charter}
 \usepackage{hyperref}
+\usepackage{amssymb}
 
 \begin{document}
 
 \section*{Homework 1}
 
 \begin{enumerate}
-\item {\bf (Optional)} If you want to look at code presented in the lectures, install Scala available from
+\item {\bf (Optional)} If you want to look at code presented in the lectures, install the 
+Scala programming language available (for free) from
 \begin{center}
 \url{http://www.scala-lang.org}
 \end{center}
 
-\noindent
-The web-applications were written in Scala using the Play Framework available from
-\begin{center}
-\url{http://www.playframework.org}
-\end{center}
+\item {\bf (Optional)} Have a look at the crawler programs. 
+Can you find a usage for them in your daily programming life?
 
-\item Practice thinking like an attacker. Assume the following situation:
-\begin{quote}\it
-Prof.~V.~Nasty gives the following final exam question (closed books, closed notes):\bigskip
+\item In the context of the course, what is meant by the term \emph{language}?
+
+\item Give the definition for regular expressions. What is the meaning of a 
+regular expression?
 
-\noindent
-\begin{tabular}{@ {}l}
-Write the first 100 digits of pi:\\
-3.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
-\end{tabular}
-\end{quote}
+\item Assume the concatenation operation of two strings is written as $s_1 @ s_2$. 
+Define the operation  of \emph{concatenating} two sets of strings.
 
-\noindent
-Think of ways how you can cheat in this exam?
+\item How is the power of a language defined? (Hint: There are two rules, one for $\_\!\_^0$ and
+one for $\_\!\_^{n+1}$.)
 
-\item Explain what hashes and salts are. Describe how they can be used for ensuring data integrity and
-storing password information.
-
-\item What are good uses of cookies (browser cookies)?
+\item Given the regular expressions $r_1 = \epsilon$ and $r_2 = \varnothing$ and $r_3 = a$.
+How many strings can the regular expressions $r_1^*$, $r_2^*$ and $r_3^*$ each match?
 
 \end{enumerate}