Figure 4.12:
DOMifier view of “itemlist” XML snippet.
The Big Picture
These nodes somehow need to fit together in the DOM tree. All the different nodes have
restrictions as to which nodes can be their children. The parent-child relationships can be
easily shown using a tree diagram, which has been split up among Figures 4.13 through
4.19. Figure 4.13 starts with the Document node, and the remaining figures flow from
there. The property, such as childNodes, that is used to get access to a node is written in
the line between nodes. These properties are described in greater detail in
Chapter 5
.
Nodes that reside under NodeList or NamedNodeMap collections don’t have a property
name because they are accessed with the item(x) method.
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Figure 4.13:
Allowable nodes under the Document node.
Figure 4.14:
Allowable nodes under the Element node.
Figure 4.15:
Allowable nodes under the Attribute node.
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Figure 4.16:
Allowable nodes under the EntityReference node.
Figure 4.17
: Allowable nodes under the DocumentType node.
Figure 4.18:
Allowable nodes under the Entity node.
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Figure 4.19:
Allowable nodes under the Notation node.
DOM Applications
You might be wondering why the DOM is needed to display an XML document in a
browser. In fact, the DOM doesn’t always need to be used when accessing XML data. A
Web page that simply wants to display the contents of an XML document can just point
the URL to that page. An XSL stylesheet can be associated with that XML document to
provide a certain view of the data. Also, CSS can be used to render the display of the
XML document. The DOM comes into play from a script when the XML document needs
to be modified or when the script needs access to some of this data. For example, a
script might need to calculate the tax on a given item at an online shopping site. Any
application that requires the manipulation of the data contained within an XML document
needs to use the DOM interfaces.
On the server side, the DOM is used heavily to process XML documents. For example,
the online shopping application included with this book sends an XML document that
represents a client’s order down to the server. The object on the server uses the DOM to
view the contents of this document and then applies the necessary business logic to
complete the transaction.
Another server-side application would be to provide a translation mechanism from legacy
databases to XML (see Figure 4.20). The DOM interfaces can be implemented on top of
this database to make it seem like an XML document to users of this data. In effect, the
users of this database don’t need to know that the data is not natively stored in XML.
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