Reading Notes : Week 5 : XML

Martin Bryan. Introducing the Extensible Markup Language (XML) http://burks.bton.ac.uk/burks/internet/web/xmlintro.htm

What is XML?
-subset of the Standard Generalized Markup Language (SGML)
-designed to make it easy to interchange structured documents over the Internet
-mark where the start and end of each of the logical parts (called elements) of an interchanged document occurs

-XML does not require the presence of a DTD.
-XML system can assign a default definition for undeclared components of the markup.

XML allows users to:
bring multiple files together to form compound documents
identify where illustrations are to be incorporated into text files, and the format used to encode each illustration
provide processing control information to supporting programs, such as document validators and browsers
add editorial comments to a file.
It is important to note, however, that XML is not:
a predefined set of tags, of the type defined for HTML, that can be used to markup documents
a standardized template for producing particular types of documents.
XML is based on the concept of documents composed of a series of entities. Entity can contain one or more logical elements. Elements can have certain attributes (properties) that describe the way in which it is to be processed

XML clearly identifies the boundaries of document parts, whether it be a new chapter, a piece of boilerplate text, or a reference to another publication unlike other markup languages, HTML, XHTML.

Uche Ogbuji. A survey of XML standards: Part 1. January 2004. http://www-128.ibm.com/developerworks/xml/library/x-stand1.html
Extending you Markup: a XML tutorial by Andre Bergholz http://www.computer.org/internet/xml/xml.tutorial.pdf
XML Schema Tutorial http://www.w3schools.com/Schema/default.asp

These three sites are tutorials running through examples of XML and its applications. I initially had a difficult time noting the difference between HTML and XML, but the W3 schools site has a page on Web Primer that gives a list for what the Average Joe needs to know about site development and it gives links then to these constituent pieces in understanding the WWW: http://www.w3schools.com/web/default.asp

Question: Do HTML and XHTML serve the same purpose; meaning, do you only use one or the other on a web page?