The output of a software clustering algorithm is either flat decompositions or nested decompositions of software systems.

A \texttt{flat} decomposition does not contain nested clusters. There is one level of clusters and one level of entities. An example of flat decomposition is shown in Figure \ref{example_flat_decomposition}.

A \texttt{nested} decomposition is a decomposition that may contain nested clusters. An example of a nested decomposition is shown in Figure \label{example_nested_decomposition}.

\begin{figure} [hbt] \epsfxsize=\linewidth \leavevmode \centering \epsffile{figures/flat_decomposition.eps} \caption{An example of a flat decomposition} \label{example_flat_decomposition} \end{figure}

\begin{figure} [hbt] \epsfxsize=\linewidth \leavevmode \centering \epsffile{figures/nested_decomposition.eps} \caption{An example of a nested decomposition}