Large Product Catalogs
A large catalog stored in SGML is easily published in print, on the Web, and on CD-ROM from a single SGML archive. Individual product sheets can also be extracted from the archive automatically, and printed as individual promotion sheets.

Manual and Documentation Archives
The aerospace industry is using SGML to store large archives of documentation about aircraft maintenance. When a new manual needs to be produced on a specific topic such as avionics or on a specific series of airplanes, a search and conversion utility can find and format the appropriate information. SGML also facilitates the creation of interactive electronic technical manuals and interactive courseware.

Online Information Delivery
The Canadian Department of National Defence uses SGML to reduce manual usage. The average field technician used to have to carry up to 18 pounds of manuals; field technicians now carry light-weight portable computers and search SGML archives to get the specific information they need, when they need it.

How does SGML translate into so many formats?
Conventional documentation programs (word processors, desktop publishers, multi-media) each have a different way of storing information, which means they cannot easily exchange the same documents. SGML can translate into so many display formats because, in its raw format, it is not concerned with the way in which the contents of a document are displayed, but rather with the types of information a document contains. The information in an SGML document is interspersed with a special type of meta-information, known as tags, which describe the information's structure and content. These descriptions may be used by a converter or a browser to define the display of the various types of information contained in the document. A single SGML file may contain any kind of information--text, graphics, video, sound, even the contents of a database. An SGML converter can be designed to isolate any number of individual information components of in SGML document, and produce a separate new file for each one, catered to fit the appropriate publishing platform. An SGML browser can be configured to immediately display each different kind of information it finds in an SGML document, whether that means playing a video, showing an image, or printing a hardcopy.

How Does SGML Work?
SGML is a simple, text-based annotation (or tagging) standard used to describe the contents of a text or multimedia document. An SGML document consists of content (information) and annotation (mark-up). One part of a typical SGML document may contain basic text, and look like this:

<PARAGRAPH>The quick brown fox jumped over the lazy old dog.</PARAGRAPH>

Another part may contain a specific kind of text, and look like this:

<ENGINE PART>Piston</ENGINE PART>

And yet another part may refer to a video file, and look like this:

<VIDEO SOURCE="FILE///sunset.mpg">

In each of the above cases, there is content ("The quick brown fox...," "Piston", the sunset video) and there are annotations ("<PARAGRAPH>" "<ENGINE PART>" "<VIDEO SOURCE="FILE///sunset.mpg">") The annotations describe what the information is, not what it should look like. The content can be any form of electronic information. An SGML file, then, is a collection of information with tags that describe that information.

Follow the Rules
While the information in an SGML document may be described with SGML annotations (mark-up), it may only be described according to a specific set of possible tags. Every SGML document must be accompanied by a kind of legend or key which explains the mark-up used in that document. Each individual legend, or set of pre-defined SGML mark-up, is known as a Document Type Definition (DTD) or a Rules File. Different DTDs may be created for different types of documents, but each individual document must follow only its own DTD. An SGML DTD outlines all the possible mark-up for particular class of documents and specifies where the different mark-up can go; An SGML document is made up of electronic information described by some or all of the types of mark-up defined in the corresponding DTD.

How Does SGML relate to HTML?
If some of the mark-up above looked a lot like HTML, that's because HTML is SGML. HTML is actually one set of pre-defined SGML mark-up: it's a DTD. It simply happens to be such a widely accepted DTD that it is sometimes confused as a language itself. HTML files are collections of information with mark-up describing that information. HTML browsers such as Netscape and Mosaic read the mark-up in HTML files and decide how to display the appropriate information based on that mark-up.

How Do I Start Using SGML?
You'll need the following things to get started with SGML:

Electronic Information
You should have information you want to access in a variety of ways (print, CD-ROM, on the Web) or a need to manage your information efficiently. Compare the following list with your information needs; SGML offers a solution for these situations:

• I'd like my information to be easily exchanged between different computers and software.
• Users of my information should be able to select the information they want in very sophisticated ways.
• I want the same information to be presented in whatever publishing format best suits the needs of the user.
• My information needs to be long lived: I want to re-use it with many applications, over time and extend its shelf-life.

DTDs
For each type of document you want to publish or view, you'll need a separate Document Type Definition (DTD) (you won't need a different DTD for separate instances of the same type of document) You can write DTDs yourself, have a consultant write them for you, or use an existing DTD.