1. Allyson Falkner Spokane County ISD afalkner@spokanecounty.org
Introduction to XML
Allyson Falkner
Spokane County ISD

2. Overview Why XML? What is XML? Example XML document
General rules of well-formed XML
Parts of an XML document
Applications for XML

3. Why XML? SGML (Standard Generalized Markup Language)
an all encompassing markup language
big and complex
software to manage it is expensive.
HTML (HyperText Markup Language)
Simplistic
no separation of style
XML (eXtensible Markup Language)
Flexibility of SGML
Simplicity of HTML

4. What is XML? A set of rules to store and organize any information
Open Standard developed by W3C (
Unicode is it’s standard character set
Separates content from style
Very Structured

5. Example XML document <?xml version=“1.0”?>
<memo priority=“important”>
<to>Sara</to>
<subject>Reminder</subject>
<message>Don&apos;t forget, <emphasize>SWIG</emphasize> tonight!
<graphic fileref=“smiley.face.pict”/></message>
<from>Allyson</from>
</memo>

6. General rules of well-formed XML
must begin with the XML declaration
must have one unique root element
all start tags must match end-tags
XML tags are case sensitive
all elements must be closed
all elements must be properly nested
all attribute values must be quoted
XML entities must be used for special characters

7. Parts of an XML document
Document Prolog
Elements
Attributes
Entities
Others
Comments
CDATA
Namespaces
Processing Instruction

8. Document Prolog XML declaration
Version
Encoding
standalone
Document type declaration (root element type)
Document type definition (DTD)
Internal subset
Entity declarations
All or part of DTD

9. Elements Container element <name att1=“val1” att2=“val2”>
…content…
</name>
Empty element
<name att1=“val1” att2=“val2”/>

10. Element Name Names can contain letters, numbers, and other characters
Names must not start with a number or punctuation character
Names must not start with the letters xml (or XML or Xml ..)
Names cannot contain spaces

11. Element Content element content (elements only)
simple content (text only)
mixed content (both text and elements)
empty content

12. Attributes name=“value”
Attribute name must be distinct within the element tag
Cannot contain multiple values

13. Caution about Attributes
Only data about data should be stored as attributes because:
attributes cannot contain multiple values (child elements can)
attributes are not easily expandable (for future changes)
attributes cannot describe structures (child elements can)
attributes are more difficult to manipulate by program code
attribute values are not easy to test against a DTD

14. Entities General entities Parameter entities (used in DTDs) %name;
Character entities
Predefined character entities (amp, apos, gt, lt, quote)
Numbered character entities (ç or ç )
Named character entities (must be predefined ISO-8879)
Mixed Content entities
Internal – declared in doc prolog
External – in another file
Unparsed entities
<!ENTITIY smiley SYSTEM “/images/smile.gif” NDATA GIF>
Parameter entities (used in DTDs)
%name;

15. Others Comments CDATA (character data) Processing Instructions
<!– text and markup 
Cannot contain two dashes
Cannot go before xml declaration
CDATA (character data)
<![ CDATA […text…]]>
Processing Instructions
<?name data?>
Namespaces
No external DTD so difficult to use
Cant validate

16. Applications for XML Communicating among applications over the web
Storing databases
Transforming data
Repurposing data (display and use server different ways)
Defining special data (math, music,graphics …)
Sharing data (news paper articles, …)