Week 10 Reading Notes

Introducing the Extensible Markup Language (XML)

·      XML was created as a way to make web documents more interchangeable.

·      The starting and ending points of elements are clearly marked.

• The language looks similar to HTML to me but a bit simpler.
• DTD – Document Type Definition
• XML DTD seems to keep users from making small mistakes, such as skipping a step when entering headings.  
• HTML doesn’t check for this – one would find out only after they wrote the code and tried to view it!
• XML doesn’t need DTD – it assigns a default definition for unspecified components.

“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.”
•  I like how clearly this information is presented. I can see the value and purpose of XML.

“XML is formal language that can be used to pass information about the component parts of a document to another computer system.”

• This is a very important thing to remember – XML is not a standardized coding method.
•   “XML is based on the concept of documents composed of a series of entities.”
•  “XML provides a formal syntax for describing the relationships between the entities, elements and attributes that make up an XML document.”
•  “XML sets out to clearly identify the boundaries of every part of a document.”
• This makes XML stand out from HTML.
• Overall, I think XML sounds easier to understand and use. XML seems more flexible and customizable than HTML, although HTML is still a strong foundation.

Uche Ogbuji. A survey of XML standards: Part 1. January 2004.

•  I wasn’t able to access this article from the given URL or through an Internet search. I was directed to IBM’s homepage but could not navigate from there.
•  From searching IBM’s website using the title, “A survey of XML Standards: Part 1”, I was taken here: http://www.ibm.com/developerworks/library/x-stand1/index.html.
• Could you provide us with a working link to this article?

Extending Your Markup: An XML Tutorial

• “XML is important for presentation, exchange, and management of information.”
• XML is a semantic language; it allows authors to specify meaning in a document.
• XML allows for more explicit annotations.
• An XML document starts with one prolog and contains one element.
•  Elements can be nested – this is like HTML!
• Attribute values must be in quotes; tags must end with either “/>” or be otherwise closed.
• This is also found in HTML.
• DTD describes the structure of an XML document. They can be terminal or nonterminal.
• DTDs were also designed to standardize data exchange between users.
• Namespaces allow for clarification. For example, they can clarify the difference between an email address and a postal address.
• Tagnames within a namespace need to be unique! For example: mybib is used to define the author in the example.
• However, namespaces and DTDs do not always work well together.
•  XML extends HTML’s linking capabilities.
• “href” refers to the URI with a fragment identifier.
•  “XSL” is “extensible style sheet”.

W3 Schools: XML Schema Tutorial

•  “An XML schema describes the structure of an XML document.”
•  I see this more clearly as I work through the XML tutorial on the W3 schools website. XML schemas also make it easier to define data patterns, validate if one has entered elements correctly, and to convert data between different data types.
•  I’m looking forward to the practical application of XML schema in class on Monday!