1. Web Programming Maymester 2004
Basic XML Concepts
Web Programming
Maymester 2004

2. XML fundamental concepts
XML is not a language, but a structure for defining application-specific mini-languages
Tags, elements and attributes
Tag names can be ANYTHING (depends on application

3. Example XML document

4. XML/HTML entities
Some symbols cannot appear in document content because they confuse parsing
Entities represent these symbols
<
>
&
&
"
“ (double quote)

5. Well-Formed XML document
Every tag has a matching closing tag
Tags are properly nested
You can have an empty element, which is its own matching close tag
<danger voltage=“480” />
All attribute values appear in quotes

6. Valid XML document A valid document must be well-formed
In addition, the document conforms to a language definition
The language definition specifies possible tags, their contents, and their attributes
Two types of language definitions:
Document Type Definition (DTD)
XML Schema

7. Document Type Definition
Example: a letter contains a source and destination address, a salutation, one or more paragraphs, and a closing

8. DTD Attribute Definitions
REQUIRED: must always appear
IMPLIED: optional
FIXED: required, and always has same value

9. DTD Data Types & Quantifiers
#PCDATA =“parsed character data”, can contain no XML markup chars
Use entities to replace markup chars
“X+” means one or more instances of X
“X*” means zero or more instances of X
“X?” means zero or one instances of X

10. Where to put DTDs
Can be embedded in the DOCTYPE declaration, as in previous example
SYSTEM DTD refers to a file on the same machine:
PUBLIC DTD gives a URL to the DTD:

11. XML Schema
Document definition file is also an XML document, unlike DTD
Gives much tighter control over contents of XML document
See for details

12. XHTML HTML that conforms to XML format
Stricter grammar rules than HTML 4.01 Strict
All tag names in lower case V

13. Acknowledgements Examples taken from Sun J2EE tutorial,