API design recommendations for facilitating conversion of single-user applications into collaborative applications

Recent advancements in collaboration technology have shown that it is possible to convert existing single-user applications into real-time collaborative applications without modifying the source codes of the single-user applications. Such conversion relies on the API (Application Programming Interface) provided by the single-user applications. Poorly designed APIs make such conversion difficult, inefficient, or even impossible. Until now, it is not well understood what features APIs should provide to facilitate conversion of single-user applications into collaborative applications. This paper presents recommendations of the features single-user application APIs should provide to facilitate conversion. The results are based on what we have learnt from converting Microsoft Visio, into real-time collaborative Visio (CoVisio), and our previous experience in building CoWord and CoPowerPoint.