What's the difference between the components ending in .system and .module in the Bug tracking system? I am a phd student focus on automated testing of complex systems and I selected the Drupal system as a case study. 
First, I need to examine the bugs recorded for a number of modules in Drupal. Thus, I looked in the issues of each module, e.g. File module https://drupal.org/project/issues/drupal?text=&amp;status=All&amp;priorities=All&amp;categories=1&amp;version=All&amp;component=file.module . But, I noticed that there exist file.module and file.system components in the issues for Drupal. And, this happens with most of Drupal modules. Thus, my question is what is the difference between file.module and file.system in the issues. I need to recorded the bugs associated to each module, so I do not know if a need to consider the bugs of .system components or .module components or both.

Thanks in advance,
Best
You're reading things slightly wrong.

There's no file.system component, or any other component ending with .system.

There are systems:


ajax system
batch system
file system
etc...


These are for issues pertaining to parts of Drupal that are not located in a module. Anything in the /includes folder of a normal Drupal installation, basically. (ajax.inc, batch.inc, file.inc for the examples above)

Then there are modules:


blog.module
file.module
menu.module
etc...


These are for module-specific issues.