How to undo TTW changes to dexterity content type

I have notices that types created with paster on the file system can be changed using the TTW editor.

When I reinstall the product the TTW changes persist, and the model file seems to be ignored. How can I discard these changes? Is there a guide to the relationship between web changes and file system changes?

Solution

A content type's entry in the portal_types tool has 3 properties related to where the model is loaded from. They are checked in this order:

model_source: The XML model, inline
model_file: Path to a file which contains the XML model
schema: Dotted path to a Python schema

My guess is that you need to make your filesystem product's installation profile explicitly empty model_source, so that it won't take precedence over model_file and schema.