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Introduction to XML and XSLT

Why XML? Comparison with HTML
XSLT - Tools for Presentation

Why XML? Comparison with HTML

Presentation vs. Content - Form vs. Function
- One of its main benefits is the total separation of content and presentation information - between what the data means, and how it should be displayed to users. For example, instead of using HTML tags to define what size some text should be on the screen (such as <font size="+3">), an XML document would use tags to specify what the text block signifies (such as <chaptertitle>).
- examples of HTML tags - some for form, some for function
- examples of XML tags used in EJ database
eXtensible (eXtensible Markup Language. ) - XML allows you great flexibility to define the specifics of the content you want to mark up. Like HTML, XML contains tags "<...>" for describing elements. Unlike HTML, XML by itself does not define any specific tags, but only describes a way to define your own tags. But this does make it more difficult to exchange data with others' implementations. Standards and tools for such exchange are being developed.

XSLT - Tools for Presentation

XSLT is a part of the XSL style sheet language, focused on transforming one XML object into another, and is extensively used throughout our projects.
- Online Bookstore examples:
  - HTML Record / Display
  - XML Record / Display (MSIE) /
  - XSLT Style Sheet1 / Sheet1 Display (MSIE) /
  - XSLT Style Sheet2 / Sheet2 Display (MSIE) /
Currently, this transformation is the most tricky part. Not only do we have to use XSLT to manipulate the XML data into the look we want to present, we have to use some complicated scripting to get the output to display correctly on different browsers. This gets more difficult when dealing with Chinese characters. Many of the technologies are still in a developmental stage.
By separating the content from presentation, we can use different XSLT style sheets to display the information in different ways for different needs, or even to show different portions of the data.
- Those using WAP phone might trigger an XSLT document to extract and display only the most relevant information in a style appropriate for their small screens. And different XSLT documents might be used for authenticated versus public access.
Where to do the transformation? On the server or the client browser?
- We chose to perform the transformations on the server:
  - Can be overly resource-intensive (slow) on older computers.
  - We know we have the tools on the server, the clients may have different versions, be incompatible with our transformation goals, or be unable to handle XML documents.
  - Greater data security - if needed, we can authenticate the user, and only send those portions of each record which they are authorized to see.

For much more information on XML and related standards, visit http://www.xml.com/ and http://www.w3.org/

Also take a look at "Using XML and XSLT to process and render online journals" if your institution has a subscription to the electronic version of Library Hi-Tech.