An open-architecture transactional file system is described. In one described implementation, a file system comprises a plurality of interchangeable and/or customizable logic layers configured to manage operations on behalf of an application when the application makes data requests to a data source. Functionality associated with the file system is augmentable by substituting and/or modifying one or more of the plurality of interchangeable and/or customizable logic layers, respectively, enabling the file system to function with many different types of data sources.