Accessing Data in the Cloud

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The Surveys application stores its data in the cloud using a combination of Windows Azure tables and BLOBs. The mobile client application needs to access this data. For example, it must be able to retrieve survey definitions before it can display the questions to the phone user, and it must be able to save completed survey responses back to the cloud where they will be available for analysis by the survey creator.

Goals and Requirements

The mobile client application must be able to reliably download survey definitions and reliably upload survey responses. Making sure that surveys download reliably is important because survey creators want to be sure that surveys are delivered to all potential surveyors in order to maximize the number of responses. Making sure that surveys upload reliably is important because survey creators want to receive the maximum number of completed surveys, with no duplication of results.

The developers at Tailspin are aware that some surveyors may have limited bandwidth available, so they wanted to control the amount of bandwidth used to transfer data between the phone and the service. In addition to this, the developers at Tailspin want to make sure that the application performs well when it transfers data to and from the cloud.

The developers also wanted a solution that was as simple as possible to implement, and that they could easily customize in the future if, for example, authentication requirements changed.

Finally, again with a view to the future, the developers wanted a solution that could potentially work with platforms other than Windows Phone 7.

Overview of the Solution

Tailspin considered three separate aspects of the solution: how to implement the server, how to implement the client, and the format of the data that the application moves between the phone and the cloud.