Sybase PowerDesigner XML User Manual page 206

Generating an XML model from an Object-Oriented Model
194
You can only generate an XML model from the active OOM diagram
window.
To update an existing XML model by generating from an OOM:
1 Select Tools Generate XML Model to display the XML Model
Generation Options dialog box.
If you do not have an XML model in the current workspace, the Update
existing XML Model option is not available.
2 Select the Update existing XML Model radio button.
3 Select a model from the Select model dropdown listbox, if the current
model has already been generated.
or
Click the Ellipsis button, beside the Select model dropdown listbox, and
select an existing model in the Select a model dialog box.
Preserve modifications
Select the Preserve modifications check box if you want to preserve
objects in the XML model.
If you clear this check box, all existing objects in the XML model will
be removed from the model, leaving only the objects generated from
the OOM.
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