Is XML the Answer to Everything?

By Kay Ethier & Scott Abel

Everywhere you turn these days, someone is talking Extensible Markup Language (XML). Jump into a discussion about publishing - XML is touted as a means of exchanging information. Talk with someone about the new software tool she is creating - she describes setting up some of her actions in XML. Ask a webmaster what he’s been doing - he raves about the dynamic content he’s serving up to site visitors using XML from a database. In short, XML is a great solution to a wide variety of challenges, and it seems to be everywhere. But is it the cure for every data or content challenge? The simple answer is, no.

What is XML?

XML is meta markup language that is used to create new markup languages. It’s most commonly used to create tag sets and processing instructions that describe structured content for presentation in text documents, but it can also be used to describe, manage, and deliver content of all types (text, images, voice, forms, multimedia files, and so on) and to transform transactional data between disparate database systems.

Unlike Hypertext Markup Language (HTML), which is a display markup language with a predefined list of tag sets designed solely to control how information is presented in a web browser, XML presents content in an open, standards-based, media-neutral, operating system-agnostic, platform-independent format. XML is extensible because it allows organizations to define their own sets of tags, each with a meaningful (semantic) “name”. Semantic names (or tags) are more useful than generic HTML tags because they can describe content in real-world, user-friendly and context-specific ways. For instance, the XML tag is much more descriptive than the HTML tag <h2>.

In a traditional word processing environment, the formatting data is stored with the content it governs, and changes to the formatting involve changes to the content itself. XML’s strength comes in its ability to separate content from formatting data, thus allowing authors to create content without spending unnecessary time formatting that information. XML style sheets control the formatting of the content being created, and specify how it will be presented in each medium.

XML content can therefore be automatically transformed (with the help of style sheets) from a single text source into a variety of information products (printed product brochures, web site content, wireless content, etc.) each with its own look and feel. And, XML content can be personalized and delivered dynamically on the fly, based on the specific requirements of the end user.

XML also differs from HTML in that it allows documentation to be processed by computer software programs, thus allowing organizations to reuse content from disparate data repositories, and recombine that data in ways – and in various media - not possible with HTML. XML supports single source content reuse, and allows organizations to make changes to a content element (like a product description) and have those changes reflected instantly and automatically in every information product that uses that information, regardless of the medium. This ability to reuse information and to make changes once and have them appear globally saves organizations considerable time and money revising, updating, and translating content.

XML content is also “validated” against document guidelines encoded in a Document Type Definition (DTD) and can enforce standards on the authors who develop content. This ability is particularly useful in validated or regulated environments (life sciences companies, legal firms, automobile and aerospace industries, the financial sector) in which completeness, consistent structure, and accuracy of information are all essential, if costly regulatory compliance and legal issues are to be avoided.

W3C Goals for XML

After the World Wide Web explosion, Web users were inundated with miles of good and bad HTML, and the W3C sought a better solution for publishing, cataloguing, locating, retrieving and archiving data. The guidelines they set for this “something better than HTML” resulted in the development of XML. The “design goals” for XML, which set it aside from HTML, include the following (Source: http://www.w3c.com/)

XML shall be straightforwardly usable over the Internet.
XML shall support a wide variety of applications.
XML shall be compatible with SGML.
It shall be easy to write programs, which process XML documents.
The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
XML documents should be human-legible and reasonably clear.
The XML design should be prepared quickly.
The design of XML shall be formal and concise.
XML documents shall be easy to create.
Terseness in XML markup is of minimal importance.

Next month, this article will focus primarily on the second W3C requirement for XML, that it plays well with a variety of tools that perform various tasks. And since the potential uses of XML are countless, and space is limited, we've restricted our scope to the use of XML in publishing.

This part of the article was first published in February (2005) issue of Interface, newsletter of the STC Hoosier Chapter. http://www.hoosierstc.org/newsletter/february2005.shtml. It is reprinted in Indus with permission from Interface. The content might have undergone some changes in compliance with the editorial policy of Indus.

Kay Ethier is an Adobe Certified Expert in FrameMaker 7.x. In 2001, Kay co-authored the book XML Weekend Crash Course (Wiley/HungryMinds). She has most recently been a contributing author on Advanced FrameMaker (TIPS Technical Publishing) and XML and FrameMaker (Apress). Scott Abel is a technical writing specialist and content management strategist whose strengths lie in helping organizations improve the way they author, maintain, publish and archive their information assets.

This column focuses on the current trends in technical communication with regard to the economy, domain, technology, documentation, management, and employment. To write in to this column or to share your comments, questions, and suggestions, please write to the column editor, Sita Bhatt.

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