[citation needed] One of the main challenges in building collaborative real-time editors is in concurrency control.

Operational transformation (OT) can incorporate concurrent changes made to replicas of the same document.

This means systems built with OT allow multiple users to make concurrent changes to the document, and all changes will be incorporated.

[3] In CoWord, OT is implemented in a module called Generic Collaborative Engine (GCE).

GCE is also provided as a library package, allowing other developers to create real-time collaborative editing systems without having to implement OT.