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One area where efficiency is potentially low, however, is that the state of the system documents list is not very visible once one is within the add document page. A For instance, the user might forget the names of all her documents and accidentally try to give one of her documents a name she has already used. We can prevent overwriting by checking the documents list before adding any new document and returning an error for multiple entries (or renaming), but this requires the user to make an additional edit to change the document name. On the other hand, incorporating the list of all documents on the add documents page would clutter the screen and possibly be confusing in its own right.
Error Prevention
Perhaps the most serious error a user could make is to set an appointment for the wrong day. This error is not totally preventable without the ability to read the user's mind, but the chance of it appearing can be reduced through visibility. Currently the user simply types in a date. That is efficient, but prone to error. One way we could make the date the user is choosing more visible is to show its position on a small calendar near the place the date is typed.
In general, however, most errors possible with this interface are typos or accidental deletions. We can't prevent typos, but because the interface is so visible they are likely to be caught by the user. Since this design doesn't visibly keep track of deleted items, accidental deletions are difficult to recover from. We can make such deletions less likely by requiring the user to confirm deletions before they are carried out.