Readings for 11-8 - 11-13

An Introduction to the Extensible Markup Language (XML)
This article did a good job of explaining the basics of XML.  Basically, from what I gather, XML is a subset of the Standard Generalized Markup Languare (SGML) that makes it easier to interchange structured documents over the Internet.  XML files mark where the beginning and end of each parts of an interchanged document occurs.  I thought the discussion on what XML allows users to do was important. (Ex. allows bringing multiple files together to form compound documents, allows the addition of editorial comments to a file, etc.)  I thought one of the most important sections of the article was the discussion of what XML is not.  It is not a predefined set of tags that can be used to markup documents, and it is not a standardized template for producing particular types of documents.  A final note that I would like to touch on is the idea that XML sets out to clearly identify the boundaries of every part of a document, which is different than any other markup languare.

Extending Your Markup: An XML Tutorial
This tutorial was very good at providing the basic fundamentals of XML without getting overly technical.  In this article, XML can  be defined as a semantic language that lets people meaningfully annotate text.  XML documents look a lot like HTML documents, but there are significant differences (Ex. different symbols and headings used for describing things.)  The discussion on DTDs was very helpful.  They basically define the structure of XML documents, and are easy to think of as context-free grammar.  The most interesting part of the article, to me, was the addressing and linking section.  Basically, in HTML documents, URLs only point to a document.  In other words, they do not address specific information within the document.  With XML, one can extend HTML's linking capabilities with three supporting languages: Xlink, XPointer, and XPath.  This "upgrade," if you will, can make finding information within linked documents so much easier.

A Survey of XML Standards: Part 1
Although sometimes confusing, this article did present information about XML standards that were necessary in order to understand the general principles when using XML.  Since this article deals mainly with the standards that are constantly being developed for XML, I would like to discuss the section about the many different standards organizations.  For most standards organizations, the first thing to be addressed is a recommendation, which are suggestions for futher standardization.  These recommendations usually become de facto standards in their own right.  The recommendation becomes a working draft, which then becomes a candidate recommendation.  The final step is for the candidate recommendation to become a proposed recommendation, which usually ensures its status as a full-blown standard after that.  Some of the major standards organizations are the W3C, ISO, OASIS, IETF, and the basic XML community.

XML Schema Tutorial - W3Schools
The W3Schools tutorials are very good because they keep information to a minimum, while giving examples of what they are talking about  in the text.  Generally, an XML schems is an XML-based alternative to a Document Type Definition (DTD.)  XML schemas describe structures of an XML document (just like a DTD.)  The main reasons that XML schemas are better than DTDs is that they are extensible to future additions, they are richer and more powerful than DTDs, they are written in XML already, and they support data types.  As mentioned earlier, the two most compelling reasons to switch to XML schemas over DTDs is because they are more powerful than DTDs and they are already written in XML (DTDs are not.)  The future for XML schemas seems to be bright because on May 2, 2001, the W3C formally recommended that XML schemas should be used.  This means that it will likely become the new standard.