One benefit of Software-as-a-Service (SaaS) is the ability to rapidly deploy iterative improvements without requiring users to upgrade the application on their machine. However, the need to rapidly "develop and test" different versions of an application implies that developers need branch isolation to protect the system from local changes to both data and meta-data in the same way that they traditionally use branch-isolation to protect the system from sourcecode changes. Providing branch-isolation for source-code changes has well-known solutions, but these solutions do not extend well to providing isolation for changes to data and meta-data. EVERETT provides developers the ability to safely - and concurrently - change database values with new business logic or evolve data schema in various ways while sharing the same database. © 2010 IEEE.