Intro to XML
   
  1. You know that XHTML is, in essence, HTML that follows the rules or syntax of XML (extensible markup language). The most important of those rules are:
    • Tags must be lowercase
    • All non-empty elements must have closing tags (e.g. </p>)
    • All empty elements must have a closing slash (e.g. <br />)
    • All values of attributes must be quoted (e.g. <tag attribute="value">
    • All tags must be properly nested (e.g. <b><i>Some bold, italic text </i> </b>
  2. As we've said, you must also add a document-type declaration to the XHTML file:
    <!DOCTYPE html public "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1l/DTD/transitional.dtd"> and add reference to the XHTML namespace in the <html> tag:
    <html xmlns="http://www.w3.org/2010/xhtml">
  3. SO, what is XML? Here is a page that summarizes a first look at XML. There are lots of deep forums, but here's an FAQ page for later, and one place for a good overview and tutorials.
  4. Here is a sample XML page. Note the syntax (and the fact that browsers can read it). The +/- are to collapse tags.
  5. Here is a first page I built that qualifies as "well-formed." recall from the review that that means it follows the rules of XML (or XHTML) syntax.Your assignment for right now is to create a similar page in Notepad or TextEdit for an address book (a common XML file), a news and events page, a publications page, a staff list, a menu, etc. that has at least three entries.
  6. Next, here is the same file that now qualifies as a valid document because it has an internal DTD (document type definition) which tells the browser where to find the rules, if any, for interpreting the tags. Note that the DTD rules are apparent only in the source code. To check those you would need an XML parser like the one here, but it needs to be on a local drive, not the Web server. Also XML schemas are replacing DTDs.
  7. XML can be styled with XSL or CSS. Here is a Version of Twelfth Night styled with CSS (be sure to take a look at the CSS file). There is nothing new there for you. For you to style your file from step 5., you should declare the document as standalone (<?xml version="1.0" standalone="yes"?>) as in step 6. You could create a DTD (or better, a schema), thus making it a valid XML document. Then you could add a CSS stylesheet (<?xml-stylesheet type="text/css" href="mystyle.css"?>) or use XSLT (see handout).
  8. Finally, here is a page that generates HTML, with attributes, with the XSL file built using XSL (eXtensible Stylesheet Language) which includes XSLT, a means of Transforming XML into HTML, PDF, etc. This tutorial gives a brief introduction, and you can check out zvon.org.

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