Extending Your Client Base With XML
Hypertext Markup Language (HTML) is the most widely used language for developing Web pages and Internet-based applications. But with this popularity comes the realization of the limitations that HTML possesses. HTML is very limited to the types of document processing it can do. And with the introduction of hand-held computers and increased use of Internet based applications, it must now support additional devices and provide more functionality. Fortunately, there is a language that can support these types of devices as well as the diversity of document-type processing for your AS/400--Extensible Markup Language (XML).
XML provides a framework for defining document markup languages. With XML you can define your own markup language much easier than with HTML and XML-enabled devices can understand the information much easier and internally process it much faster. In many cases, the types of actions that XML can accomplish are impossible with HTML. It is for this exact reason XML was created.
How does XML compare with HTML? HTML's limitations include restricting the user to a relatively small set of tags. These tags are part of the HTML standard and therefore limit the author to the point that they cannot create their own customized tags. Tags that are not part of the HTML standards are not recognized by Web browsers and therefore cannot be interpreted by them.
XML overcomes the limitations of HTML and other languages by providing capabilities that were not part of the earlier languages. In an XML document, the tags identify the meaning of the data they contain. The structure of the XML data is far easier to understand. It is based on the names given by the programmer and is not cryptic or vague. In comparison to HTML tags, names reveal little about the meaning of their content. This makes it harder to update the data or the format in the event of policy or system changes. The structure is not particularly useful for manipulating because the names and tags are not easily identifiable. This type of interchange may require much more programming and is increasingly difficult to maintain, as this information has to be shared between applications.
XML documents require three components. The first is an XML-enabled device. These devices manipulate the information into a viewable format for the user. They can range from browsers to cell phones to handheld calendars. There are not yet many devices that support XML, but this will change as its popularity grows.
The second component is server-based, namely the WebSphere application server installed on the AS/400 under V4R4. WebSphere is currently available as a non-chargeable product for the AS/400. XML on the server consists of servlets and applications that process the server-side XML code. The Web server can also be configured to serve static XML pages similarly to static HTML pages, where there is no server-side processing done. Through the use of Java Server Pages (JSPs), Java Servlets, JavaBeans or Enterprise JavaBeans, a programmer can connect to the AS/400 data and services so that they can be included into XML documents. The database connectors connect the applications to the necessary AS/400 data.
The last component is the data that the XML server-side process extracts information from. This is the source for the dynamically created XML documents. The servlets have the capability to return the data in XML format for direct transmission to the client or returning the data in JDBC format. This provides a better method for Java-based applications to access the data. It can then be manipulated into a manageable format for the client to interpret.
This new feature of WebSphere extends the capabilities of the AS/400. Your AS/400 can now be used to serve information to devices other than browsers. This can be used to view the status of your servers or to share information with remote users who do not have access to Internet-based devices.