ChannelManager: Three components
October 20, 1997
Seybold Report on Internet Publishing
Vol 2, No 2
ChannelManager manages content, presentation and the user interface with three major components:
- ChannelServer, which installs inside Netscape or Microsoft Web servers, and serves as the content and presentation router.
- ChannelClient, a Java applet that runs on top of Java-capable, 32-bit Web browsers and functions as the user interface to the channel directory and to the channel content itself.
- ChannelBase, a repository that stores its metadata in ODBC-compliant databases. The database stores user profiles as well as documents
ChannelServer. Users log on to the DataChannel server with a password. ChannelServer translates client requests and filters incoming channels according to notification and configuration rules. The server has authentication rules that enable "nomadic" access. Based on user IDs, the server fetches and sends the appropriate frame objects and URLs from ChannelBase to the client. The server supports Excite, Lycos and Yahoo search engines.
When the password is verified, the server generates a SQL request to ChannelBase. ChannelBase responds with a display profile and channel links based on a look-up of user preferences This provides a nomadic, personal desktop—one that gets loaded from the server whenever you log on, from wherever you are.
Configurable clients. One of the nice aspects of keeping content and presentation separate is that new and different clients can be designed without waiting for an upgrade to the underlying data format. This approach also makes it easier for a single customer to utilize client software from a variety of vendors, all of which recognize a common data format.
There are actually three types of clients for ChannelManager: ChannelClient, a collection of Java applets; Pax Syntactica, an experimental XML applet available for free download; or the generic XML-capable browsers of the future, starting with the beta release of Microsoft Internet Explorer 4.0.
The production-ready client today is ChannelClient, which can open other application windows or become the entire user interface for HTML pages and Java applications. The basic look is built on hierarchical lists of channels, tabs and items. Assuming ten of each, the user has access to 1,000 pieces of information within three clicks. Will all types of information readily fit this hierarchical paradigm? Pool says yes, claiming, "I haven’t found anything that I can’t describe as a hierarchical list."
Pax Syntactica is a 400K Java applet that downloads an XML parser, graphical interface and channel logic onto a window in the client machine (Figure 3).
The XML viewer anticipates how client software will handle XML-encoded data in the near future, but Pool has no ambition as a browser developer. "Our goal is to have our product replaced on the client," he said. When Microsoft and Netscape come out with browsers that handle XML metadata, Pool claims that DataChannel will be pleased to ease out of the viewer business and focus on the repository and server software that feeds such viewers.
While the document is still in HTML, its XML metadata becomes the table of contents—the navigator to the document. John Tigue, senior software architect, says, "It’s your bookmark.htm file on steroids."
The navigator is created from the tags of the metadata, such as these snippets in Channel Definition Format (CDF):
<Title>Welcome to DataChannel’s ChannelWorld</title>
<Abstract>Welcome to DataChannel’s ChannelWorld</abstract>
<Author Value="Lisa Rein" />
<title>What’s going on with Novadigm suing Marimba?</title>
<abstract>The Novadigm vs. Marimba dispute is over a different specification, the DRP submission, not the OSD submission. </abstract>
It is this sort of markup that publishers will soon be adding to their Web pages, making it easier for visitors to use search engines, Web browsers and other navigation aids to zero in on the information they seek.
ChannelBase. The ChannelBase repository holds the indexes, descriptions, URLs and presentation characteristics for the content of each frame in a desktop template. It contains user templates for individuals and groups. Objects stored within ChannelBase can point to pages, channels, corporate databases, Java applets and ActiveX components.
Connection to ChannelServer is provided through an ODBC interface. For connecting to XML processors, ChannelManager supports XAPI-J, an XML API written in Java by Tigue.
Administration. Once ChannelManager is installed and connected to a local database, configuring it is a point-and-click process. Content is organized as items within tabs within channels. Figure 4 shows the interface for creating a new item.
On a different tab, administrators create or edit user properties (Figure 5). User properties include the usual identification and authentication parameters plus user preferences for presentation characteristics for the user’s desktop. Administrators create groups and then assign individuals to groups of one or more.
Channel management consists of subscribing users or groups to published (available) channels (Figure 6).