![](bga.png)
Figure 8: Screen of error message observed after playing
back an input sequence to exercise the counter example.
[ERROR] DispatcherUtils - Could not execute action
<java.lang.NullPointerException>java.lang....
at com.apress.ajaxprojects.theorganizer.actions.
DayAtAGlanceAction.execute ...
at sun.reflect.GeneratedMethodAccessor80.invoke ...
...
Figure 9: A part of server log observed after playing back
an input sequence to reach the counter example.
machines (FSMs) that correspond to the behavior
of the AJAX based web applications.
• Model checking the generated FSM based on the
user-given properties
Once the models are generated, various properties can
be checked very quickly. Also, for the model gener-
ations, the proposed technique can accept “guidance
directive” to target user-specific features and behav-
iors of the AJAX based web applications. These have
been confirmed through experiments. Industrial sized
applications can be processed within reasonable time.
Future works include more verification trials with
larger applications for more robust evaluations of the
proposed techniques as well as their extensions. On
verification trials with larger-scale applications, the
performance of model generation stage in our tech-
nique which is taking relatively long time, can be im-
proved with several strategies.
While we have introduced model reduction tech-
niques in Section 3.1.3 to reduce run time, use of the
state abstraction technique which removes DHTML
substructure unrelated to verification requirements,
was limited in the experiments. Although more ag-
gressive model reduction configuration based on ver-
ification requirements is expected to reduce time re-
quired for model generation stage, the prospect has to
be confirmed through case studies.
Most of time required for crawling-based model
generation stage is from communication latency be-
tween the crawler and the target application. As com-
putation burden of the process is relatively small, it
is desirable to introduce parallel crawling technique
used in conventional web crawler. There is an ongo-
ing work of parallelizing the process in CRAWLJAX
project, and the outcome is expected to be effective
for reducing run time of our verification flow.
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