CMS 2005: Lazy Version Control

In a multi-user system, a problem can arise when two or more users edit the same document simultaneously. This is known as the “lost update” problem, and occurs when, for example, user A opens a document, and user B opens the same document, such that the last user to save their copy of the document overwrites the changes that have been made by the other user. The traditional approach taken by content management solutions to prevent this problem has been to force users to checkout documents when they wish to edit them, and then check them back in when they have finished.

System 7 CMS, however, does not use this approach for a number of reasons. Firstly, studies of its application in practice clearly show that it generates problems of its own, for example where users checkout content, and then absent-mindedly forget to check it back in, forcing other users to find the errant user or seek the assistance of an administrator. Secondly, studies also show that in practice, situations where simultaneous editing of content would occur are quite rare, and number does not justify the productivity overhead generated by check-in/check-out systems.

For the purposes of maximizing productivity, convenience and optimizing user experience, System 7 CMS instead uses a system called “lazy version control”. Whenever a user begins editing a content item, their copy is automatically moved to a “temporary editing area” (with the purpose of preventing the creation of a new version on every minor change and providing continuity between Web sessions). When the users finishes editing the content, before it is copied back from the temporary area the system checks that the original copy has not been changed since editing began.

If the original document has changed since editing began, the system notifies the user and prompts them to either cancel the save operation or overwrite the changes made by another user and the user examines the original document and merges the changes prior to saving again. In most publishing applications this happens so rarely that the case for removing the check-in/check-out overhead is overwhelming. However, using a special optional “content locking” feature, publishers can also implement a check-in/check-out process if they desire.

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