Microsoft Word Applied xml a toolkit for Programmers Wiley doc

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Ceponkus, Hoodbhoy - Applied XML - Toolkit for Programmers

Microsoft Extensions

Figure 4.20:
Conversion of legacy data to XML.
The Future of the DOM and Its Current Limitations
The current DOM Level 1 specification defines only the necessary constructs to expose
and manipulate an XML document. Future versions are in the works to address some of
the following limitations:
•
DTD or Schema validation support
•
A multiple user mechanism to allow an XML document to be edited by multiple users
in a structured manner
•
XSL stylesheet support
•
An event model
The DOM is currently in its infancy, which has given rise to some extensions to DOM
implementations. Using nonstandard extensions in DOM implementations may provide
much needed functionality, but also limits an application’s target platform to only one
implementation of the DOM. In other words, extensions should only be used when there’s
no standard way of doing the same thing.
Microsoft Extensions
In the Microsoft XML parser bundled with Internet Explorer 5, the parser adheres to the
DOM Level 1 Core specification. In addition to DOM Level 1 Core compliance, some
extensions have been added that might be useful or destructive to an application. Some
of these extensions are useful because they compensate for some of the limitations in
the DOM specification.
DOM limitations that the parser addresses include:
•
A definite way of loading an XML document. Unfortunately, the specification does not
specify the syntax for loading an XML document.
•
A mechanism for persisting the XML tree model to an XML document.

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•
Support for datatypes in elements and attributes.
•
Stylesheet transformations from script.
•
Identification of parse errors.
•
Asynchronous XML document downloading capability.
As interesting as some of these features sound, be forewarned that these extensions can
prove to be destructive to your application, because the application only works with the
MSXML parser. A Web page that uses the DOM interfaces could suffer from using
extensions, since those extensions won’t be available in other browsers.
Summary
In this chapter, we went over what the DOM is and why you may want to use it as your
application programming interface. It is important to understand what a node is and how it
interacts with other nodes to form a tree. In this chapter, we presented a conceptual model;
details on how to use the model are discussed at length in the
next chapter
.

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