Changes can be filtered to not trigger a build; if none of the files within a change are contained in the view mask, the build is filtered.
For example, with a View Mask Filter of:
//depot/main/tests
-//depot/main/tests/001
Case A (change will not be filtered, as index.xml is in the view mask):
Files:
//depot/main/tests/index.xml
//depot/main/tests/001/test.xml
Case B (change will not be filtered, as index.xml is in the view mask):
Files:
//depot/main/test/index.xml
//depot/main/src/build.xml
Case C (change will be filtered, as no file is in the view mask):
Files:
//depot/main/src/build.xml
Case D (change will be filtered, as no file is in the view mask):
Files:
//depot/main/src/build.xml
//depot/main/tests/001/test.xml