![](bg8.png)
Figure 11: Global PP comparison between Q1 and Q2.
Finally, the time to answer each question (up to
five minutes) could be considered as a threat to va-
lidity. We chose this short time to avoid the test sub-
jects spending too much time “exploring” the graph
database and to limit the learning effect. But given the
results, it may appear a little too short since some sub-
jects reported that they may have been able to build
more compositions with more time.
5 CONCLUSIONS
We proposed an approach that searches for sequences
of services to build a SoS. Sequences of services al-
low a task to be implemented not only by one service,
but by any existing composition of services. An eval-
uation found that our approach resulted in composi-
tions of higher quality (based on our notion of “point
percentage”) compared to an approach based on find-
ing services in a composition one-by-one.
Future work include improving the quality of the
Mule ESB configuration file parser by adding sup-
ported Mule ESB elements and structures. Another
enhancement would allow more flexibility for the use
of the graph database with a graphical interface to vi-
sualize, search and edit the graph database, keeping
consistency with the indexes. Finally, a third exten-
sion concerns the structure of the generated composi-
tions, still limited to linear sequences whereas Mule
ESB can handle choices, fault handling, etc.
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