The ABL UI Designer editor is the default design editor and ABL Editor is the default
source editor for the valid procedure .w files. The valid
.w files means the procedure files which are created using
the standalone AppBuilder or GUI Designer using OpenEdge AppBuilder perspective in
Progress Developer Studio for OpenEdge.
Note: You must be in the
OpenEdge AppBuilder perspective to work with the .w files
created in the GUI Designer or standalone AppBuilder application.
The procedure .w files created with the GUI Designer or
standalone AppBuilder are indicated with an AppBuilder 
icon in the Project Explorer view.
Note: There may be .w files in an OpenEdge project
that are not created using the GUI Designer or standalone AppBuilder. Such
.w files do not open with the GUI Designer editor,
instead open with the ABL Text editor.