The datasets used come from the NASA/MDP and the SoftLab data sets\footnote{The datasets can be obtained
at \url{http://promisedata.org}} from the Promise Data
Repository\cite{promiseData}. 

The NASA/MDP datasets used are: CM1,
KC1, KC2, KC3, MC2, MW1, and PC1. These datasets were chosen for
examination because they represent a wide variety of projects. 
A frequently posed objection to using the NASA datasets in a Cross-Company examination is that all the datasets are written for a single organization, and do not represent a proper sampling of software styles and development procedures. When writing about software defect datasets from NASA, Zimmermann et al. states:
\begin{quote}
For their study Turhan et al.\cite{08Turhan} analyzed 12 NASA projects (mostly in C++) which they considered cross-company because they were all developed by contractors under the umbrella of NASA. However, all projects had to follow stringent ISO-9001 industrial practices imposed by NASA, so it is unclear to what extent the data can be actually considered cross-company.\cite{cc}
\end{quote}
Menzies et al. retorts that:
\begin{quote}
"NASA is a much more diverse organization than is commonly appreciated. NASA software is written by layers of contractors working for different companies around the nation. Arguing that all ISO-compliant organizations are the same is like saying that a CMM level3 weapons manufacturer is writing the same software as a CMM level3 finance company."\cite{menzies0x}
\end{quote}

The NASA
datasets represent projects such as flight software, storage
management, video guidance systems, and an experiment
framework\cite{08Turhan}. Also, the majority of the data used in the NASA datasets is from ground control software, not flight control. As such, it is not as constrained during its development. Menzies et al. shows empirical evidence that the NASA datasets represent truly different development practices and methodologies.

The SoftLab datasets are AR3, AR4, and AR5. These datasets were chosen for examination because they represent a different spectrum of products, decreasing the similarity of the tested datasets. While the NASA datasets are usually large, and highly critical systems, the SoftLab datasets represent the embedded systems in some Turkish white goods. The embedded systems control three separate appliances including a washing machine. These datasets differ from the NASA/MDP datasets in their severity, scope, and purpose.
%TODO: What type of systems are these? Asked Ekrem on 3/5.

The files have been modified from their original form to allow them
to be used in cross company experiments\footnote{Cross company
experiments use $n - 1$ of $n$ datasets for training, and the $n^{th}$ for
testing}. They have been modified to unify the columns used, and their
orderings. The data is stored in the arff format for easy integration
with the WEKA experimenter\cite{weka}. 

\input{figures/attribute-clustering-main}
\fig{attribute-clustering-main} shows the attributes present in each dataset. Attributes marked with a "X" are used in both the Within Company and Cross Company experiments. The attributes marked with a "W" are only used in the within company experiments. These datasets will be used in all further studies unless noted otherwise. 
