How to conditionally build other projects?

If I understood it correct you should be able to do this by following these Steps:

1. First Build Step:
   1. Does the regular work. In your case: building, unit testing and packaging of the web application
   2. Depending on the result let it create a file with a specific name.
   3. This means if you want the low-risk-change to run afterwards create a file low-risk.prop
2. Second Build Step:
   1. Create a Trigger/call builds on other projects Step from the Parameterized-Trigger
      plugin.
   2. Entery the name of your low-risk job into the Projects to build field
   3. Click on: Add Parameter
   4. Choose: Parameters from properties File
   5. Enter low-risk.prop into the Use properties from file Field
   6. Enable Don’t trigger if any files are missing
3. Third Build Step:
   1. Check if a low-risk.prop file exists
   2. Delete the File

Do the same for the high-risk job

Now you should have the following Setup:

• if a file called low-risk.prop occurs during the first Build Step the low-risk job will be started
• if a file called high-risk.prop occurs during the first Build Step the high-risk job will be started
• if there’s no .prop File nothing happens

And that’s what you wanted to achieve. Isn’t it?