Web Services, Part VIII: Reading DTDs with JavaScript

In this column we continue our series on Web services. In Part I, we introduced you to this hot topic. In Part II, we showed you how to call Web services. In Part III, we presented the WebService behavior and its four supported methods. In Part IV, we continued our coverage of the WebService behavior by describing its objects and properties. In Part V, we dove into XML and XSLT. In Part VI, we started a miniseries on how to load and manipulate XML files from JavaScript. We continued this miniseries in Part VII, and focused on the DOMDocument's nodes and node types. In this column, we dive into the world of document type definitions (DTDs).

The XML format supports entity references. These are parameters you can substitute with real values upon loading. These real values are defined in the DTD file. In this column we'll show you how to interact with DTDs. We'll teach you how to assemble a DTD for both document structure validation, as well as entity substitution. We'll show you what the DOMDocument object looks like in case of entity referencing, and how to insert new entity references into a DOMDocument.

In this column you will learn:

• How to assemble and call DTDs
• How to define an XML file structure
• How to reference and specify entities
• How to load DTDs with a browser
• How to load DTDs with JavaScript
• How to add entity references on the fly

You can find a listing of our XML, XSL, and DTD files on Page 8, or you can download them directly from this zipped file.