of communication is limited by network latency. This creates a fundamental dilemma: users need their own edits incorporated into the document instantly, but if they are incorporated instantly, then because of communication latency, their edits must necessarily be inserted into different versions of the document.

An example illustrates this problem. Suppose Bob and Alice start with a document containing the word Mary. Bob deletes 'M', then inserts 'H', to change the word into Hary. Alice, before she receives either edit from Bob, deletes