A schema-based device service that provides centralized access to per-user device data, wherein access to the device data is based on each user's identity. The device service includes a schema that defines rules and a structure for each user's data, and also includes methods that provide access to the data in a defined way. The device schema thus corresponds to a logical document containing the data for each user. A service such as a notification/alerts service accesses data in the logical document by data access requests through defined methods, such as in order to customize or modify a notification for a device based on the device characteristics. In one implementation, the device schemas are arranged as XML documents, and the services provide methods that control access to the data based on the requesting user's identification, defined role and scope for that role.