Over several years the number of different devices that can access the web has increased, with a corresponding change in the range of their capabilities. Not only do devices differ in physical characteristics, they can also differ in the protocols that they support. Bandwidth has improved, the range of access paths has been extended, and user expectations have kept pace with this change.
Over several years the number of different devices that can access the web has increased, with a corresponding change in the range of their capabilities. Not only do devices differ in physical characteristics, they can also differ in the protocols that they support. Bandwidth has improved, the range of access paths has been extended, and user expectations have kept pace with this change.
It no longer makes practical or business sense for publishers and content providers to develop material for a single channel or technology. Rich content and applications now need to be delivered to a range of devices with a minimum of effort.
A delivery context is a set of device properties that defines a delivery environment, and can be used to provide information in a format and style that match the capabilities of the device. MCS handles a range of delivery contexts by selecting or adapting the content to match a particular device profile. As an author, you create content once, and then tailor it to different devices using a combination of layout and style. This means making a clear distinction between device dependent and device independent information by separating it into several parts.
Content may be static information, or dynamic data retrieved from an external source in response to a query. In MCS you use XDIME markup, an XML vocabulary that is in many ways similar to HTML and WML. In addition, XDIME has a number of special elements to support device independent content, and the inclusion of dynamic datasources.
MCS manages the relationship between device-independent content and device-dependent data by using policies and variants. For example, an image policy can refer to a set of image files, or variants, which individually fit the profiles of several different devices. The attributes of each variant are contained in the policy. In an XDIME 2 page, the object element's src attribute value is set to the name of the image policy. When a device requests the page, MCS uses the image attributes to select the best image variant to display on the device.
Layouts contain the device dependent positioning for information rendered on a variety of displays, where limitations of small devices may require that content be split or even omitted
Themes govern the style of a site across multiple devices. The thematic information for a device is termed a style, and a style contains rules that are appropriate to the delivery context.
This separation of aspects of site development maps to the skills required to build it. Layouts and themes provide the presentation layer of the site, allowing content to be developed independently.
To learn more about standards development on device independence refer to the W3C Ubiquitous Web Applications web site.