Reading Notes: XML

XML is a difficult concept to understand.  It is not a programming language, like Java, which uses  functional elements.  XML doesn't designate style elements, like HTML.  In a sense, it doesn't really DO anything.   It's basically a carrier and organizer of information.

XML is important because it allows different computers to interchange documents via the internet.  You use XML to create your own tags which label the parts of information in a document.

< name > Jane < /name >

< role student < /student >


This way a person or a computer can identify the elements in a document easily and without ambiguity.  XML is advantageous because it is a somewhat simplified version of SGML that lets you set document structure.  HTML is very valuable in telling a computer how to display information on the web but it says nothing about the type of information that is the content of the document.

XML allows the user to create a list of elements tagged in a standardized way.  The elements can be defined with attributes which give qualifying information about the attribute (i.e. gender, color, length, number, etc.).  This can be done with quotation marks inside the original statement or in a separate statement.  

The user can determine things like how to manage white space, language, and allowable characters.  XML is useful for creating a detailed catalog.

DTD allows users to list and specify their own tags as well as set the order of their tags (XML does not impose a specific order on a list of elements).   A DTD is a formal document which defines the roles of the elements labeled by the user.  XSD (XML schema definition) can be used instead of DTD to define the structure of a document.   XSD offers extensibility, consistency, power, and support for data types and namespaces (w3schools.com)

Namespaces: allows a user to differentiate between two different elements with the same name (this happens most often when XML is combined with HTML).

Questions:
*Can you please explain the use of xlms atrributes and the use of URIs ?  I'm not sure I fully understand this concept.
*Can you clarify the different between terminal and non-terminal elements?


Sources:

1. Martin Bryan.  Introducing the Extensible Markup Language (XML) http://burks.bton.ac.uk/burks/internet/web/xmlintro.htm  
2. Uche Ogbuji. A survey of XML standards: Part 1. January 2004. http://www-128.ibm.com/developerworks/xml/library/x-stand1.html 
3. Extending you Markup: a XML tutorial by Andre Bergholz http://www.pdffinder.com/pdf/extending-your-markup-an-xml-tutorial.html, or at http://xml.coverpages.org/BergholzTutorial.pdf
   
4. XML Schema Tutorial http://www.w3schools.com/Schema/default.asp 
5.