Device Detection and Characteristics

To be able to resize images and carry out other kinds of adaptation requires that you know the characteristics of the devices.

Most devices (desktop and mobile) send information about the content formats and character encodings they support, but they usually don’t provide enough details for a particular application. Some, but not many, devices present some information as non-standard HTTP headers. But in any In any case, it’s impractical for devices to send all the information that is needed for adaptation in their headers.

The answer is a database of information known as a Device Description Repository. Currently, the standards world is doing a lot of work on this subject.

The W3C and OMA are working together to create a standard framework for storing useful information with dotMobi actively participating because of its importance to the Mobile Web.

In the meantime, other solutions exist for finding out device characteristics.

One of the better known is WURFL. This open source project maintains and updates a range of information about a multitude of devices. There are APIs which help you access this information from server side scripting.

Another source is the OMA-inspired UAPROF. UAPROF puts an additional header in the HTTP request containing the URL of a file with information about the requesting device. If it hasn’t got the file already, the server can find this URL and request the information about the device.

Several companies provide commercial services around Device Descriptions. Mobile Wizards, for example, has collected thousands of UAProfiles and offers free and fee-based services for this information.

Other companies like Volantis, MobileAware, SevenVal, Drutt and Argogroup offer value-added services, including specialist online adaptation services.