Platinum Edition Using HTML 4, XML, and Java 1.2
(Publisher: Macmillan Computer Publishing)
Author(s): Eric Ladd
ISBN: 078971759x
Publication Date: 11/01/98

If you had an HTML file that contains your Active Desktop Component setup on a server, you could place the component into the channel with CDF code such as the following:

<ITEM HREF=”http://www.server.com/channelz/desktop-comp.html”>
   <USAGE VALUE=”DesktopComponent”></USAGE>
</ITEM>

If you set the VALUE attribute of the <USAGE> element to DesktopComponent, then you can use several other elements between the <USAGE> and </USAGE> elements. These include

•  <CANRESIZE VALUE=”YES|NO”/>—Enables the user to resize the desktop component. The default value is YES. This element has precedence over the <CANRESIZEX/> and <CANRESIZEY/> elements.

•  <CANRESIZEX VALUE=”YES|NO”/>—Enables the user to resize the desktop component in the horizontal direction. The default value is YES.

•  <CANRESIZEY VALUE=”YES|NO”/>—Enables the user to resize the desktop component in the vertical direction. The default value is YES.

•  <HEIGHT VALUE=”pixels”/>—Sets the initial height of the desktop component.

•  <OPENAS VALUE=”HTML|Image”/>—Specifies how to open the component. An HTML document is opened using the HTML <IFRAME> element. Images are opened using the <IMG> element. The default value is HTML.

•  <WIDTH VALUE=”pixels”/>—Sets the initial width of the desktop component.

Controlling Log Recording

If you want to make sure that an entry appears in the page hit logs every time a certain <ITEM> is served, you can use the <LOG/> element to accomplish that. <LOG/> takes the VALUE attribute, which, for now, can take on only the value “document:view”. By placing the <LOG/> element between the <ITEM> and </ITEM> tags, you instruct Internet Explorer to make a log entry whenever a document specified in the <ITEM> is accessed.

You can also specify where the log files should be sent by using the <LOGTARGET> element. <LOGTARGET> takes the attributes shown in Table 17.4.

The SCOPE attribute splits page hits into two categories: OFFLINE for browsing that has occurred from a local disk cache, and ONLINE for browsing over a connection to the Internet. The default value of SCOPE is ALL, so that all page hits are sent during the log file transfer.

The <LOGTARGET> element may only occur once in a channel, and it can contain the following two standalone elements:

•  <HTTP-EQUIV NAME=”header_name” VALUE=”header_value”/>—<HTTP-EQUIV/> specifies what kind of HTTP header should be put in front of the log file as it is sent. The most common value for NAME is “Encoding-Type.” An <HTTP-EQUIV/> element that handles a compressed zip file, for example, might look like
<HTTP-EQUIV NAME=”Encoding-Type” VALUE=”zip”/>

•  <PURGETIME HOUR=”hours”/>—Suppose you want log entries only from the past 12 hours and nothing prior to that. You could use the <PURGETIME/> element as follows:
<PURGETIME HOUR=”12"/>
to ensure that the entries in the transferred log file are not more than 12 hours old.

Making a Channel Password-Protected

Security is uppermost in people’s minds when they’re on the Internet, so any precautions you can take to ensure the security of channels—particularly channels with sensitive information—will be appreciated by end users. The CDF specification includes a <LOGIN/> element that you can use to require authentication before a user enters a channel. When initially subscribing to a CDF-based channel, a user would be prompted for a username and password to use with the channel.

CDF-Compliant Software

For users to fully appreciate the work you put into creating your channel, they have to have a client program that is CDF compliant. Internet Explorer is an obvious choice for this, but other push technology vendors have embraced CDF as the way to go for authoring managed content channels. Some of these companies include

•  AirMedia

•  BackWeb

•  DataChannel

•  FirstFloor

•  Torso

•  Wayfarer

Additionally, PointCast has thrown its support behind the CDF specification. Netscape’s Netcaster can support CDF in a limited way because of a less powerful site-crawling scheme.

Creating Channels with Microsoft FrontPage

CDF is a markup language the same as HTML is, and creating a CDF file can be as easy as creating an HTML file. You can open up a simple text editor such as Notepad and type out your CDF file, or if you prefer a more automated approach, you can use the Channel Definition Wizard that comes with Microsoft FrontPage. The wizard walks you through several steps during which you’ll build the channel by adding items, setting up update schedules, and configuring log files. This last section of the chapter takes a look at the Channel Definition Wizard and shows you how simple it is to make a channel out of an existing Web page.