http://stackoverflow.com/questions/5702391/mvcs-model-view-controller-service Service layer can be inerpreted a lot of ways, but it's usually where you have your core business processing logic, and sits below your MVC architecture, but above your data access architecture. For example you layer of a complete system may look like this: View Layer: Your MVC framework & code of choice Service Layer: Your Controller will call this layer's objects to get or update Models, or other requests. Data Access Objects: These are abstractions that your service layer will call to get/update the data it needs. This layer will generally either call a Database or some other system (eg: LDAP server, web service, or NoSql-type DB) The service layer would then be responsible for: Retreiving and creating your 'Model' from various data sources (or data access objects). Updating values across various repositories/resources. Performing application specific logic and manipulat