diff --git a/text/preliminaries/data.tex b/text/preliminaries/data.tex
index 06feaf2..af16337 100644
--- a/text/preliminaries/data.tex
+++ b/text/preliminaries/data.tex
@@ -1,8 +1,8 @@
-\section{Data}
+\section{Types of data sets}
 \label{sec:data}
 
 
-\subsection{Categories}
+\subsection{Data categories}
 \label{subsec:data-categories}
 
 The data that we are interested in, contain information about individuals and their actions.
@@ -39,7 +39,7 @@ In incremental data, an original data set is augmented in each subsequent timest
 For example, trajectories can be considered as incremental data, when at each timestamp we consider all the previously visited locations by an individual, incremented by his current position.
 
 
-\subsection{Processing and publishing}
+\subsection{Data processing and publishing}
 \label{subsec:data-publishing}
 
 We categorize data processing and publishing based on the implemented scheme, as: