If you have experience with structured authoring, representing structured documents in XML, or transforming XML into HTML using XSLT, you will recognize many aspects of this application's design.Adobe AIR, Flex, and XML combine to create a compelling platform for delivering applications.

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But it was only with the introduction of XML (and all the associated tools to support processing XML, such as XSLT) that it became cost-effective for structured authoring to gain broad adoption.

In this example, I used Adobe Frame Maker to author the structured document.

The content of the document (text, graphics, and so on) is organized into a hierarchy of elements and attributes, and the rules dictating how the content is tagged and organized are described in a schema or Document Type Definition (DTD) as shown in Figure 3.

Years ago, it was common in certain industries (such as aerospace) to represent structured documents in SGML.

In a production environment, you would either have to introduce a process to ensure only valid XML was provided to the viewer, or you would need to build a validation function (and corresponding exception handling) into the viewer.

Note: I could have gone with an industry-standard DTD or Schema (for example, Doc Book or DITA), but the DTD is use for this article strikes a good balance by being complex enough to represent a working scenario without being as complex as one of the industry-standard DTDs.

These components have default UI behaviors that enable you to create an application with just a few lines of code.

You will group and nest the components to match the desired presentation of the content and its structure.

Note: This article is a good starting point for someone new to Flex or Adobe AIR, because it provides a walkthrough for how a complete application can be built with surprisingly few lines of code.