XML with correct syntax is "Well Formed" XML.
XML validated against a DTD is "Valid" XML.
Well Formed XML Documents
A "Well Formed" XML document has correct XML syntax.The syntax rules were described in the previous chapters:
- XML documents must have a root element
- XML elements must have a closing tag
- XML tags are case sensitive
- XML elements must be properly nested
- XML attribute values must be quoted
| <?xml version="1.0" encoding="ISO-8859-1"?> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> |
Valid XML Documents
A "Valid" XML document is a "Well Formed" XML document, which also conforms to the rules of a Document Type Definition (DTD):| <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE note SYSTEM "Note.dtd"> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> |
XML DTD
The purpose of a DTD is to define the structure of an XML document. It defines the structure with a list of legal elements:| <!DOCTYPE note [ <!ELEMENT note (to,from,heading,body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)> ]> |
XML Schema
| <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="to" type="xs:string"/> <xs:element name="from" type="xs:string"/> <xs:element name="heading" type="xs:string"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> |
A General XML Validator
To help you check the syntax of your XML files, we have created an XML validator to syntax-check your XML. XML Viewers
If you are attempting to use XML for the first time, chances are you don't know or have the tools that are necessary to view XML files. The good news is there are a plethora of free viewers readily available to you. This lesson will show the many free XML viewers that are currently out there. Free XML Viewer
Chances are the web browser you have on your computer is XML ready. If you would like to see how your browser handles XML files, open up our XML File: class_list.xml. If your browser doesn't let you view that XML file, then read on as we describe the popular browsers and their XML viewing features. Internet Explorer XML Viewer
Internet Explorer 6.0 supports viewing XML files. You can download IE 6.0 from Microsoft's Website. Internet Explorer 6.0 has special color coding the make XML documents easier to read. Also, next to expandable elements (those that contains child elements) there is a plus or minus sign (+/-) that lets you expand or contract that element.After you have installed Internet Explorer 6.0, try viewing our XML file: class_list.xml.
Firefox XML Viewer
Firefox has some of the same features as Internet Explorer. You can download Mozilla's Firefox from Mozilla.com.After you have installed Internet Explorer 6.0, try viewing our XML file: class_list.xml
Opera XML Viewer
Unfortunately, Opera does not currently support viewing XML files, so please download one of the browsers we have listed above. If you would like to see what XML looks like in Opera, open our XML file: class_list.xml.If you are looking for an XML editor, check out our next lesson, in which we recommend an XML editor based on your needs and budget!
