1. A method for implementing a persistence application programming interface (API) that is platform independent and can make up-calls to business logic, the method comprising: receiving a request at the API to execute a command at a persistence tier of an n-tier distributed application; in response to the request, determining an entity type for an entity affected by the command; identifying a function at a middle tier of the n-tier distributed application that is associated with the entity type and the command, wherein the middle tier includes the business logic; sending an instruction to the middle tier to execute the function; and upon receiving a confirmation at the API that the function executed, executing the command at the persistence tier.