Source files, subprojects, and object files all need to have their locations specified by including the directory or folder in which they reside on the relevant path. These pathnames can be specified in either an absolute or relative manner in each function call from Shell.Project, but you must not mix both notations.
The Shell.Projectfunctions take filenames in the idiom of the underlying filesystem. For example, "~/MLW/basis/_text_io" on UNIX and "C:\\MLW\\basis\\_text_io" for Windows.
Note: The double backslash is necessary on Windows because a single backslash is the Standard ML way to signal an escape sequence. See the Definition.