With the new Active Channels feature in Internet Explorer, you can specify which content is downloaded, and when. You can provide the latest news reports and company information, and even turn that information into a screen saver. If you are a corporate administrator, you can use software distribution channels to automatically update the programs on a user's computer, through an intranet, when a new program release is available.
An Active Channel is a Web site that has been enabled for information-receiving programs such as Internet Explorer 4.0. The mechanism that makes this possible is the Channel Definition Format (.cdf) file. You can use the content you already have, such as Web pages and graphics, for channels. You may want to structure it differently so you can make sure users receive the right amount of content in an organized way.
A software distribution channel is a mechanism for updating program files (in the form of Java™ class libraries, Java stand-alone applications, ActiveX™ Controls, or platform native code) to the user's computer. A software distribution channel is based on a .cdf file and the Open Software Distribution (OSD) format.The .cdf and OSD formats are based on XML (eXtensible Markup Language), a standard for storing and transmitting structured data. Like HTML, an XML-based document holds text annotated with tags. For more information and samples, see the Internet SDK, available at the Microsoft Web site at http://www.microsoft.com/.
Users can "subscribe" to a channel to monitor it for changes and browse the contents quickly from the cache online or offline. A subscription to a channel updates the local cache with new information according to what the publisher specifies in the .cdf file. Subscriptions can be customized to either check for updated content by downloading only the .cdf file, or by downloading the .cdf file and all associated new or updated content. A channel subscription is independent of fees charged for viewing content on a Web site.
If a user chooses not to download the content, the channel hierarchy, page titles, and abstract descriptions are still updated. However, clicking an item in a channel would force the browser to navigate to the actual Web site rather than to display the contents previously downloaded into the local cache.
Channels that have been updated in the local cache are marked with a colored "gleam" on the icon representing the channel. Users can also specify an e-mail address at which they want to be notified when the subscribed channel is updated in the local cache. When a subscription is updated, the user can browse through the channel's content without being connected to the Internet (offline browsing).
The .cdf file provides an index of resources available in the channel and a recommended schedule for when the channel should be updated on the local computer. A .cdf file contains some tags that specify logos, the files to be updated, and the schedule for updating them.
If the .cdf file includes the ABSTRACT element for each item in a channel, users can view a description of those items. Abstract descriptions are displayed in a ToolTip when the user rests the cursor over the item. Web publishers can use this feature to describe the content of a particular Web page or to attract users' attention and encourage them to review that content immediately.
NoteOpen Software Distribution (OSD) provides automatic download of only the software that the user needs, and the correct version of the software. By querying users' computers about existing software and hardware, OSD can make more intelligent decisions about what users need. With new versions of software always coming out, major revisions, minor revisions, and build numbers can bewilder even hard-core users.
OSD simplifies the computing experience further by installing missing components on the fly. This means that if the user is missing a component that prevents another program from functioning, OSD can detect this and automatically retrieve the missing component for you. Users get only the components they need. Many of the tags and functions performed with OSD can also be used in .cdf files.