We are working to design online forms. Some forms are opened when they already have some of the user's personal information (like name and address).
The user can edit existing data, and enter additional information.
When the user edits the existing data, should he make explicit action that opens the field for editing? That is, if there is a table with phone numbers, should the user press the "Edit" button to make the table editable? The same goes for ordinary fields. Is it right to leave the field editable, but after each section to get a message like "Are you sure you want to change the information X?"