The Web is at the beginning of a new wave of technology—Web broadcasting, more popularly known as "Webcasting" or "push" technology. Today millions of users have the information that they want delivered directly to their desktops, using any one of several special "push" software solutions. Unfortunately, several problems stand in the way of this technology's continued progress: most of the solutions require special client and server software, they don't work well with each other, and they are fundamentally limited in their ability. To address these problems and move "push" technology to the next level, the industry needs to pull together around a common standard that optimizes information delivery.
With Internet Explorer 4.0, Microsoft is pioneering such a standard via the Channel Definition Format (CDF), along with more than 30 key industry partners. This standard offers great flexibility, allowing Web sites to choose the types of information they want to broadcast, and users to choose what they want to receive as well as how often and when they receive updates. The following Q&A exchange describes CDF and how the industry is rallying around it and Internet Explorer 4.0 as the platform for the future of push technology.
How does Internet Explorer 4.0 enable the Webcasting of information, and how does the CDF enhance that delivery?
Today the Platform Preview release of Internet Explorer 4.0 already provides an open, standards-based way to push and pull information natively without requiring any special client or server software. By using a Web-crawling agent that ships with Internet Explorer 4.0, every Web site on the Internet can effectively become a Channel publisher using basic HTTP, HTML, and other standard Internet technologies. The agent simply "crawls" through a Web site, bringing as many pages as the user has specified from the site's top-level tree down to the user's cache or hard drive. This approach is very simple; however, it is also limited in its ability to deliver only the information that the user wants. As a result, Microsoft and more than 30 leading companies in the industry have rallied behind the Channel Definition Format (CDF) as an open, standards-based way to optimize the delivery of information.
In contrast to the Internet Explorer 4.0 Web-crawling agent, CDF lets Web sites customize their information delivery specifically for the user. Now any company or information provider can author content to take advantage of CDF—without re-authoring the content itself. The CDF specification enables Web publishers to define their existing Web sites in logical groupings so users can select the types of information they want delivered.
CDF also ensures that the broadcasted information is always up to date. The information will be presented in the Channel User Interface, enabling users to quickly select the content they need. With CDF, intelligent delivery is possible, and fewer resources are used by both clients and servers.
What exactly is CDF? Why is it important in moving Push Technology to the next generation?
The Channel Definition Format (CDF) is an open, industry-standard way for Web sites to optimize the broadcast of information to users. The CDF specification allows a Web publisher to offer automatic information delivery (in the form of "channels") from any Web server to people connected to the Internet or corporate intranets. Microsoft has published the CDF specification, which is available on the SiteBuilder Network.
Basically, CDF provides an index or map of a Web site that describes the type of information contained on the site. Specifically, CDF describes logical groupings of information (i.e., sports news vs. financial information), how often the site gets updated, and how to send that information to the user so that the delivery is much more efficient and personalized. When combined with a cookie file, CDF will allow users to further customize and personalize the type of information they receive.
The CDF standard submission is an application of Extensible Markup Language (XML) work that the World Wide Web Consortium (W3C) now has in progress. This makes the CDF approach to "push" even more appropriate, as it lays the groundwork for a whole new wave of XML innovation later this year. CDF is one of many new, dynamic XML applications that act like HTML but let developers embed rich and structured information into Web pages, without the browser displaying that information to the user. Many industry experts consider XML to be the next great Web revolution.
How does CDF work?
Web authors and developers use industry-standard HTML and a CDF file to build a broadcast channel on the Internet or an intranet. The CDF file is downloaded to a user's desktop computer along with the channel. Once on the desktop, CDF adds intelligence to the user's computer, enabling it to notify the user when changes have been made to a channel so the user doesn't have to keep checking the site for updates. Once the content is downloaded, users can view it anytime—even when they're not connected to the Internet—which can significantly lower the cost of accessing information from the Web.
How do Internet Explorer 4.0 and CDF work with existing Push software solutions?
CDF is being embraced by today's leading push software vendors, including PointCast, BackWeb, Airmedia, and FirstFloor, in addition to many others. As a result, Web site authors and users will benefit from industry-wide support of the standard.
In addition, Internet Explorer 4.0 provides an open, extensible architecture that allows for easy integration of existing push software solutions. Today, users face potential conflicts and added learning time with multiple push software products on their PC. Internet Explorer 4.0 will help reduce scheduling conflicts and user interface issues by providing a standard method for users to schedule information delivery. In particular, PointCast, BackWeb, Airmedia, and FirstFloor recently announced their adoption of Internet Explorer 4.0 as their strategic platform for information delivery and are working with Microsoft to help solve these problems for customers.
How does the Webcasting feature integrate with the rest of the capabilities of Internet Explorer 4.0?
In addition to leading support for CDF, Internet Explorer 4.0 provides unique integration of push delivery throughout the entire product. In particular, Internet Explorer 4.0 provides for off-line and full-screen viewing of "channels," as well as native integration on the Windows desktop. Internet Explorer 4.0 also provides a richer set of development technologies for Web authors to create great looking Web sites and channels via leading support for Dynamic HTML, ActiveX™, Java™, and JavaScript/VBScript. For more information, see the Internet Explorer 4.0 Web site.
Detailed Questions About Microsoft's Open Approach to Webcasting
Q: How does CDF benefit end users?
A: CDF enables end users to:
- Receive information from any site as a Webcast
- Personalize and control information
- Integrate push content with the desktop
The CDF specification allows Web publishers to define their existing Web sites in logical groupings so users can select the types of information they want delivered to their desktops. When combined with a cookie file, CDF will allow users to further customize and personalize the type of information they receive. CDF also triggers computers to notify users when changes have been made to a channel, so the user doesn't have to keep checking the site for updates. Once the content is downloaded, users can view it anytime—even when they're not connected to the Internet—which can significantly lower the cost of accessing information from the Web.
Q: How does CDF benefit Web authors?
A: CDF enables Web authors to:
- Use the same Web site content for Webcasting and browsing
- Eliminate having to buy new server software to support entry-level Webcasting
- Deliver information directly to users' desktops without having to learn or use any programming languages; CDF can be implemented without writing any Java™, JavaScript, or Livescript code
- Take advantage of open standards and interoperability with other push software, including enhanced Webcasting servers that can now be rapidly introduced by third party companies
CDF benefits Web publishers through its ability to automatically optimize the delivery of existing Web site content without requiring special server software or the re-authoring of the Web site. Strong support of the CDF in existing Web authoring tools and server publishing software, such as Microsoft's Internet Information Server (IIS), means it will be simple for authors to create CDF files. Also, existing push solutions from leading companies such as PointCast, BackWeb, Airmedia, FirstFloor, and many others mean that Web site authors get the most complete set of push software solutions that work with CDF.
Q: How does CDF benefit corporations?
A: CDF enables corporate information technology staff to:
- Take advantage of easy administration and control
- Deliver a bandwidth-efficient means for Webcasting
- Deliver Webcasting without requiring any changes to proxy server software, a result of CDF being delivered via standard Internet protocols
Q: Does CDF require the use of special servers or other software?
A: No, CDF can use any HTTP server software for entry-level Webcasting. And it requires no additional software on the client side. Also, valued-added server solutions such as products from BackWeb or Marimba can work with CDF.
Q: Does CDF require any changes to existing HTML?
A: No. CDF uses the Extensible Markup Language (XML) to deliver information to the browser software about how to display and update channels, so it works with existing HTML content, rather than requiring Web authors to change any of their content.
Q: What is XML and why is it useful?
A: XML stands for eXtensible Markup Language. It's a simplified subset of SGML (Standard Generalized Markup Language, ISO 8879), specifically designed for Web applications. XML adds value because it provides three key advantages over HTML:
- Extensibility. Information providers can define new tags and attribute names specific to their applications.
- Structure. Document structures can be nested to any level of complexity.
- Validation. Applications can quickly check XML documents for structural validity without referring to an external definition of terms
Here's an example of how these might be used:
A medical application includes a patient medical history document type, which includes a <medical description> structure, with an <allergy> structure within the medical description, and <allergen> tags within the allergy structure. The medical application validates the data to make sure that the <allergen> tags, if present, are in the <allergy> and <medical description> strucutures, and not in the <patient address> structure.
Q: Will XML work?
A: Yes. XML is based on proven SGML technology, which is already in use at places such as the Library of Congress.
Q: Is XML standards-based?
A: Yes. There's an XML working group at the W3C. They published their latest working draft in 3/97.
Q: Does XML have broad industry support?
A: Yes. Led by Microsoft, XML is supported by Sun Microsystems, SoftQuad, NCSA, Hewlett-Packard and now Netscape (as of 4/97), among others.
Q: Will Microsoft support XML in Internet Explorer?
A: Yes. Internet Explorer 4.0 will support a few XML applications (such as CDF), and future versions of the browser will feature native support for XML.
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