You must create a message definition file before you can create the
message model objects. The message definition file contains the logical and
physical model definitions of the objects in XML schema form.
To create
an empty message definition file to contain your message model objects:
The new empty message definition file with the name that you have
specified and a file extension of *.mxsd opens
in the Message Definition Editor so that you can use the editor to create
your own message definitions. If you have selected to use a target namespace,
a directory structure based on the URI that you have supplied is created.
The new message definition file is placed within this directory structure,
which appears in the Resource Navigator, Outline view and Overview editor.