0.33.4: XML application model

XML applications can be deployed in a logical three-tier environment as follows:

XML and three-tier environments
Tier 1
XML-enabled user agents parse an XML document, apply stylesheets, and present the document contents. Some user agents convert the XML document to HTML for presentation. Microsoft Internet Explorer 5 is an example of an XML-enabled user agent that can display XML documents without first converting them to HTML. Although only a small number of XML-enabled user agents are available today, their number is expected to grow as the popularity of XML increases.
Tier 2
XML-based servlets and applications provide server-side XML processing. A Web server (an HTTP server) can be configured to serve static XML documents. However, to process and dynamically generate XML documents, the Web server base function must be extended. The XML Document Structure Services in the Application Server provide such an extension of the Web server and enables Tier 2 servlets (database connectors and integration applications) to parse, generate, manipulate, and validate XML-based dynamic content. This content is sent to Tier 1 and interchanged with other servlets. Tier 2 can also be used to selectively apply stylesheets to XML documents when the Tier 1 devices do not support the application of XSL stylesheets to XML documents.
Tier 3
The content for dynamically generated XML documents can be retrieved from data servers. Depending on the XML application, the extracted data can be returned as an XML document or returned in JDBC or some other format to a servlet that converts the data to an XML document. In the future, XML-capable Java beans for accessing databases should be commercially available.