Here is a canonical path.
C:/files/foo.txt
Here are absolute paths
C:/files/FOO.TXT
C:/files/FOO.txt
C:/files/foo.TXT
C:/FILES/FOO.TXT
A canonical path is an absolute unique path to the file.
A file can have only one canonical path and many absolute paths.
A file can have only have one canonical path which is the file path of the file.
A file can have many absolute paths to the file.