adding some pics

sections/overview.tex

@@ -13,8 +13,15 @@ A cycle in the dependency graph (i.e., a cell being upstream of itself) is an er
 In contrast to classical spreadsheets, where each cell is a completely independent entity, we adopt the Relational spreadsheet model~\cite{DBLP:conf/cidr/BakkeB11}, which focuses on so-called `tidy data,' where each row is one record, and each column represents a distinct (strongly typed) variable.
 This approach incentivizes usage patterns that streamline data caching and make it easier to implement on-disk: Critically, columns and type information are available in a static context even before data is loaded, while the need for dynamic data access via caching is limited to a one-dimensional index on records.
 
+\begin{figure}
+  \includegraphics[width=\columnwidth]{graphics/layers.png}
+  \caption{Stuff}
+\end{figure}
+
 \subsection{System Layers}
 
+
+
 \paragraph{Source Data Layer}
 
 An Overlay data source is primarily responsible for defining the initial shape (i.e., schema and number of rows) of the dataset, and providing random access to individual cell values.