SGML, or Standard Generalized Markup Language, is one of the core technologies currently shaping information publishing. It allows a single document to adapt to multiple publishing environments, bringing flexibility and organization to often unruly projects.
Like “style sheets” in a word processor, SGML uses “tags” in a document to convey information that plain ASCII text can’t. Unlike style sheets, however, SGML deals with the content of a document, rather than its appearance.
SGML uses textual tags, such as <subhead>, <title>, or <pullquote>, to show what type of information the text contains. SGML allows users to create their own custom markup languages to meet the needs of specific applications. For example, a poem might use tags such as <stanza> and <line>, while a newspaper’s editorial staff might use <author> and <pullquote>. These tags imbedded in the documents are invisible to users, but they allow the computer to deal with information more intelligently. When SGML-savvy software is used to manipulate a marked-up document, the software can recognize the different types of content and respond accordingly.
The World Wide Web, a hot topic for information publishers, is an example of SGML in action. HTML (HyperText Markup language) is one implementation of SGML and is used to create Web pages. HTML uses tags to provide limited layout capabilities, graphics, and links to other sites on the Internet. When new features are added to Web browsers, such as the ability to display more complex graphical images, they are simply being upgraded to support additional HTML “tags.” Most of the maior word processors and page layout programs (WordPerfect, MSWord, Nisus, PageMaker) will allow you to assign SGML or HTML tags to styles and export SGML files.
Of course, SGML is not limited to use on the Web. It is useful any time a single piece of information will be published in multiple formats:
- A longtime publisher of poetry books chose to use SGML to structure the text of poems. An unanticipated result was the ability to easily create new poetry anthologies by topic, which have increased sales while re-using available information.
- Several semi-conductor manufacturers have used SGML to structure the complex data which describes their products. This allows them to publish frequently-updated information in print, on CDROM and on-line, while their customers can re-use the information (without retyping) for their own catalogs, publications and internal product development.
- An increasing number of developers use SGML for software documentation since the information must be updated frequently and is often used both on-line and in printed versions.
- An extensive list of videos is printed as a reference book and then used in an on-line guide that is searchable by any number of criteria (director, actor, awards received, etc.). Having the text tagged also allows quick implementation of new catalogs and other on-line ideas.
Due to its versatility, all the uses of SGML have yet to be explored. The most difficult part of any SGML job is creating the ‘custom’ SGML variant that will suit a particular task. Creating an oversimplified set of tags will limit the flexibility of the system, while adding too many will bog down users with unneeded markup work.
For more information on SGML, HTML and markup languages, you may want to read Practical SGML by Eric von Herwijnem published by Klewer Academic Publishing, or Liura Alschuler’s soon-to-be published book, Creating Structured Documents. You might also consider exploring The SGML World Tour CD available from SoftQuad (Toronto) or some of the many online sources of information, including the newsgroup comp.text.sgml and http://www.yahoo.com/Computers_and_Internet/Software/Data_Formats/SGML/. For an introduction to SGML, try http://www.brainlink.com/~ben/sgml.html.
Electronic publishing and the World Wide Web are growing dramatically, and implementing the right technology now can make a world of difference in the future.