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

The STYLE attribute can be set to one of two established values: “ActiveSetup,” which tells the browser to use the ActiveSetup ActiveX engine, or “MSICD” (Microsoft Internet Component Download), which instructs the browser to look in the Open Software Distribution (.osd) file for how to do the install. Additionally, developers are free to create their own download STYLEs.

A <SOFTPKG> element resides inside a <CHANNEL> element. Inside the <SOFTPKG> element, you can have many other elements, including some you’ve already seen, such as <TITLE>, <ABSTRACT>, and <LOGO/>. Beyond those elements, a few others are useful. The <LANGUAGE/> element can be used to specify which languages the software’s user interface can support. <LANGUAGE/> takes the VALUE attribute, which is set equal to a semicolon-delimited list of ISO 639 language codes.

Another important element inside the <SOFTPKG> element is the <IMPLEMENTATION> element. <IMPLEMENTATION> provides information on the configuration necessary to install and run the software. Inside the <IMPLEMENTATION> element, you can specify various system configurations using these standalone elements:

•  <LANGUAGE VALUE=”list_of_languages”/> for which languages the software supports

•  <OS VALUE=”MAC|WIN32|WIN95|WINNT”/> for the operating system

•  <PROCESSOR VALUE=”ALPHA|MIPS|PPC|x86"/> for the type of processor

In addition to these, you can also use the <CODEBASE/> element inside the <IMPLEMENTATION> element. <CODEBASE/> takes the required attribute VALUE, which is set equal to the URL of the downloadable file. You can also have a SIZE attribute, set equal to the maximum number of kilobytes to allow in the download, and a STYLE attribute, which can be set equal to ActiveSetup, MSICD, or a style created by the developer.

Putting it all together, a sample software distribution channel might be coded like the following:

<CHANNEL HREF=”http://www.server.com/channelz/download.html”>
   <TITLE>Software Channel</TITLE>
   <ABSTRACT>Upgrades of the latest movie screensaver software that are
    available on this channel.</ABSTRACT>
   <LOGO HREF=”http://www.server.com/channelz/images/download.gif”
    STYLE=”ICON”/>
...
<SOFTPKG HREF=”http://www.server.com/channelz/download-launch.html”
    NAME=”download” PRECACHE=”YES” VERSION=”4,2,0,0" STYLE=”MSICD”>
    <TITLE>Upgrade Screen Saver</TITLE>
    <LOGO HREF=”http://www.server.com/channelz/images/scrsaver.gif”
     STYLE=”ICON”/>
    <LANGUAGES VALUE=”en;es”/>
...
    <IMPLEMENTATION>
        <CODEBASE VALUE=”http://www.server.com/channelz/scrsaver.exe”/>
    </IMPLEMENTATION>
...
</SOFTPKG>
...
</CHANNEL>

The preceding channel enables users to download version 4.2 of the screensaver program, which is stored at http://www.myserver.com/channelz/scrsaver.exe.

If you have multiple platforms to which you need to distribute software, you don’t need to set up separate channels for each. A given <SOFTPKG> element can contain many <IMPLEMENTATION> elements, so you need to specify an <IMPLEMENTATION> element only for each platform. If you are distributing to Macintosh, Windows 95, and Windows NT platforms, you might alter the preceding code to read

<CHANNEL HREF=”http://www.server.com/channelz/download.html”>
   <TITLE>Software Channel</TITLE>
   <ABSTRACT>Upgrades of the latest movie screensaver software that are
    available on this channel.</ABSTRACT>
   <LOGO HREF=”http://www.server.com/channelz/images/download.gif”
    STYLE=”ICON”/>
...
<SOFTPKG HREF=”http://www.server.com/channelz/download-launch.html”
    NAME=”download” PRECACHE=”YES” VERSION=”4,2,0,0" STYLE=”MSICD”>
    <TITLE>Upgrade Screen Saver</TITLE>
    <LOGO HREF=”http://www.server.com/channelz/images/scrsaver.gif”
     STYLE=”ICON”/>
    <LANGUAGES VALUE=”en;es”/>
...
    <IMPLEMENTATION>
        <OS VALUE=”MAC”/>
        <CODEBASE VALUE=”http://www.server.com/channelz/scrsaver.hqx”/>
    </IMPLEMENTATION>
...
    <IMPLEMENTATION>
        <OS VALUE=”WIN95"/>
        <CODEBASE VALUE=”http://www.myserver.com/channel/email95.exe”/>
    </IMPLEMENTATION>
...
    <IMPLEMENTATION>
        <OS VALUE=”WINNT”/>
        <OSVERSION VALUE=”4,0,0,0"/>
        <CODEBASE VALUE=”http://www.myserver.com/channel/emailnt.exe”/>
    </IMPLEMENTATION>
...
</SOFTPKG>
...
</CHANNEL>

Setting Up an Active Desktop Component

Active Desktop Components are really HTML files that sit on your Windows desktop. Because you aren’t viewing them through a browser, they don’t seem like HTML files, but that’s all they really are (see Figure 17.3).

You can specify a channel <ITEM> to be an Active Desktop Component by using the <USAGE> element. <USAGE> takes the single attribute VALUE, which can be set to one of the following:

FIGURE 17.3  The Active Desktop Component from the National Geographic channel launches its GeoBee game.

•  Channel—Specifies the <ITEM> to be a component of the channel. This is the default behavior in the absence of any <USAGE> elements.

•  DesktopComponent—Designates the <ITEM> to appear in a frame on the Active Desktop.

•  Email—Specifies that the <ITEM> is to be emailed whenever the channel is updated.

•  None—Specifies that the <ITEM> should be left out of the channel.

•  ScreenSaver—Designates the <ITEM> for use as an Internet Explorer screensaver.

•  SoftwareUpdate—Specifies that the component’s purpose is to deliver a software update.