The Microsoft vision of “three screens and the cloud” encompasses access to information and entertainment, irrespective of the type of device, the screen size, and the user’s location. Applications that use data exposed by cloud services can provide a compelling user experience that is appropriate for the device the consumer is using (such as a phone, desktop computer, or large screen television), and in any fixed or mobile location. This guide focuses on consuming services
exposed by cloud-based services, and in particular Windows Azurehosted services.
Windows Phone 7 applications can consume data from services implemented on any platform and operating system, using any data mechanism that exposes a suitable format and communication protocol. However, it is likely that you will aim to use standard data formats and protocols in your applications to provide decoupling and promote reuse of services. This is especially appropriate for scenarios where you expose data that may be consumed by many different types of devices.
Microsoft is evolving an end-to-end strategy for simplifying data communication between the server and mobile devices based on open standards that allow developers to target a wide range of data stores and devices. This strategy encompasses the typical requirements of receiving, sending, and synchronizing data between the server and the device. The data protocol that Microsoft is supporting as the core protocol for data transmission across the majority of its frameworks and technologies, and specifically between severs and mobile devices, is the Open Data Protocol (OData).
Note: OData defines a Representational State Transfer (REST) based mechanism that works over HTTP, and supports Atom, Atom Publishing (Atom Pub), and JavaScript Object Notation (JSON) formats. Atom is an XML-based data syndication format, while JSON provides opportunities for compact serialized data transmission. For more information about OData, see the Open Data Protocol website (http://www.odata.org/).
OData uses an HTTP verb extension named MERGE; it defines this in a way that is compliant with the protocol. Whereas the PUT verb requires all fields of a record to be specified when updating data, the MERGE verb will accept changes and use the existing values for other fields. This is beneficial because it can reduce the volume of data transmitted between the phone and the server.