Category Show-N-Tell Thursday
A typical requirement in applications is to keep a log of changes. The simplest form is to keep fields with the author and date/time of the latest change (which has the distinct disadvantage not knowing what has been changed by whom). The next level would be to keep the list of all authors and change times (still leaving the question "what
unanswered) followed by very sophisticated tools like Audit Manager
or similar home grown solutions.
All these solutions have in common, that they "merely" record changes made (typically in a query or post save event) after
they happened (From a big picture perspective, a log on query-save is technically before, but after the trigger that will commit the change). While this works reasonable well for audit, adding another typical requirement calls for a different solution. More often than not the parts of a (workflow) document which can be altered by any given user change in the course of an [workflow] application. While Author fields protect a document at large, safeguarding individual fields becomes more tedious, especially when you can't group them in access controlled sections (e.g. in a web application).
In a related use case: documents could be updated by users, who have current information, but don't "own" the documents. Typically they send an email to the document owner (if that is visible) asking for the update of that information. Asking somebody to update data into some other system, that involves copy & paste from an eMail *is* a sign of a broken process. The solution to that seemingly contrary requirements: "update of certain fields" only and "update by anybody" can be solved using a pattern that I christianed "Inversion of Logging
Instead of logging what has changed an application using this pattern creates a change request, stating what will
be changed. This request is then processed by a central system and checked against system constraints. If an authorized user requests a change, the changes are applied without further user interaction. The change request is kept as record. If an unauthorized user requests a change a workflow is kicked of to determine if the request is suitable for approval to be then routed to the data owner (or data guardian) for approval. Once approved the changes are applied to the main document.
To make this internal flow transparent and pleasant to the users a few considerations need to be made: