CompSci497
Advanced XML Programming with XmlPL
Lecture Notes
Friday, January 19th, 2007

Contents

1. A brief history: SGML, HTML, XML & XHTML
   1. SGML
   2. HTML
   3. XML
   4. XHTML
2. Data description languages, what are they good for?
3. An introduction to XML.
   1. Pros
   2. Cons
   3. Basic Syntax
   4. XML Extensions

• Standard Generalized Markup Language
• Developed in the 60's
• Created for long-term machine readable document storage.
• Complicated syntax

• Hyper-Text Markup Language
• First version appeared in 1993
• Originally an application of SGML. Later deviated from SGML standard.
• HTML is a standard maintained by the W3.org. Specifications can be found on their website.

• First standard published in 1996 by the W3.org
• Also an application of SGML
• Designed as a simplified sub-set of SGML

• Published as a recommendation by the W3.org in 2000
• XHTML replaces HTML as the new Web standard
• XHTML is a true application of XML
• XHTML is stricter in what it allows but therefore easier to parse.

• Sometimes called Metalanguages or Markup languages
• Focus on the description of data rather than on the description of computation.
• Although DDLs are often terribly verbose for describing computation, it is easy to "make up" new languages.
• Parsing data is easy. Unlike data structures in other languages like C or Java
• Data is easily interchangeable between various machines, operating systems and programming languages
• Data longevity.
• Other languages: JASON, YAML, S-expressions

• Both human and machine readable
• Fairly simple syntax. (if you stay away from DTDs)
• Easy to parse.
• Widely supported
• Hierarchical
• Easy to describe common data structures such as lists, trees and graphs.
• Unicode support

• Can be verbose
• Some features left over from SGML are overly complicated.
• Can be difficult to map to non-hierarchical relation structures such as databases.

• <name attribute="value">content</name>
• One root element
• Element children are: element, text, comment, processing instruction
• <!-- Comment -->
• Short form element: <element/>
• Special characters: &, <, >, ' and "
• Entity references: &amp; (&), &lt;(<), &gt; (>), etc.
• Numerical character references: &#169; (©)
• w3.org's specification

• Namespaces
• XPath
• XPointer
• XML Schema