Ordering Child Elements

Consider the following DTD snippet....

	<!ELEMENT CONTACT (NAME EMAIL)>
	<!ELEMENT NAME (#PCDATA)>
	<!ELEMENT EMAIL (#PCDATA)>

In this case, we expect to see XML along the lines of:

        <CONTACT>
        <NAME>Jim Sanger</NAME>
        <EMAIL>sanger@sanger.com</EMAIL>
        </CONTACT>

Alternatively, the following code would be valid:

        <CONTACT>
        <EMAIL>sanger@sanger.com</EMAIL>
        <NAME>Jim Sanger</NAME>
        </CONTACT>

Notice that since we simply listed the children of CONTACT as a space delimited list, we do not specify any order in which the children should appear. Had we used a comma to separate the list, we would be forcing an order. Thus if we redefined our DTD to use:

	<!ELEMENT CONTACT (NAME, EMAIL)>
	<!ELEMENT NAME (#PCDATA)>
	<!ELEMENT EMAIL (#PCDATA)>

Then the following XML would be valid:

        <CONTACT>
        <NAME>Jim Sanger</NAME>
        <EMAIL>sanger@sanger.com</EMAIL>
        </CONTACT>

but the following XML would be invalid because the EMAIL element would not be allowed to precede the NAME element.

        <CONTACT>
        <EMAIL>sanger@sanger.com</EMAIL>
        <NAME>Jim Sanger</NAME>
        </CONTACT>

Defining Elements and their Children
Introduction to XML For Web Developers | Table of Contents
Repeated Elements