%MozillaXHTML11; %MozillaMathML; ] > A guide to the Standard Generalized Markup Language and its role in information management ArborText, Inc. Ann Arbor, Michigan 18 October 1995 1992, 1995 Arbortext, Inc. This file may be redistributed electronically as long as it remains wholly intact, including this notice and copyright. This file must not be redistributed in hard-copy form. Arbortext will freely distribute this document in its original published form on request. As the world standard for textual information, SGML has gained prominence in many industries. Hundreds of companies have adopted SGML and thousands are considering it. If your organization produces a high volume of technical or business information of significant value, and if that information lends itself to a regular structure, then SGML probably offers significant benefits to you and your organization. This White Paper examines the factors that led to the development of SGML, the basic knowledge you need to understand SGML, the reasons for adopting SGML, lists those industries where SGML use is already widespread, and lists resources for more information and training. The explosive success of the Internet is an obvious example of an information revolution that's well under way. Companies that realize the tremendous cost and value of information management are reengineering their processes for creating, distributing and accessing information. The opportunities in each of these areas can be enormous: By some estimates, 20% of our GNP is spent on generating new information. And over 90% of that information is in documents, not databases. When was the last time you took a close look at how much your organization invests in the creation of information? In conventional word processing and desktop publishing systems, your authors spend up to 30% of their time searching for information, and another 30% of their time applying styles and squeezing paragraphs so that each printed page looks nice. Plus, nearly every 18 months, technology changes completely, so you're continually paying for data conversions as software and hardware become obsolete. A few years ago, you could provide your information on paper alone. Then CD-ROM technology became low-cost and widespread, so you've either already faced or soon expect to face the massive re-publishing effort needed to make all your information available electronically. And in just the last year, the &www; has thundered out of nowhere, creating yet another new format for your information. At the same time, your customers want your information tuned to their needs: they don't want to wade through huge technical manuals that describe all system variations and all possible uses for all possible users; they want information tailored to their own needs, so they can get to it and use it fast. In the U.S. alone, businesses produce 92 billion documents every year; and that number is skyrocketing. Can your people easily access the information you create in your own company? How about the information you receive from other companies? An organization's future can depend on how effectively it identifies, manages, and uses its information. The latest thinking in information management takes an enterprise-wide approach to the creation, distribution and maintenance of information. Organizations that have taken this broad view have realized enormous improvements in the cost, accuracy, timeliness, accessibility, and variety of the information they create and use. As part of this movement, companies in some industries are joining together to develop standards for exchanging information with each other and with their customers. Companies that keep up-to-date with these standards will be able to do business more efficiently and compete more effectively in global markets. This white paper describes how one such standard, the Standard Generalized Markup Language (SGML), works as part of an overall information management strategy. Traditional documents and the methods for handling them suffer many limitations. The printed document is often the result of a sophisticated information process. Once it's printed, however, the document represents a dead-end in the information flow because it has no link to the electronic information base. Raw data may start in the form of technical specifications or engineering data. This information must be gathered, sorted, organized, and then manually assembled into hard copy documents. With each step in the documentation process, the information may have changed by mistake. The further removed the result is from the original source of information, the greater the risk of erroneous data. The problem can become so large that a majority of documents go out of date as soon as they are printed. A systematic approach to information management treats text and graphics as part of an organization's electronic information base. This gives everyone access to the information. By taking a broad view of the information creation and delivery process, you can see documents as any composition of information; the output from a database query, a printed document, an on-line diagnostic manual, an illustrated parts catalog, a collection of video clips, or a home page on the Internet's &www;. SGML allows you to manage information as data objects instead of characters on a page. Rather than a stream of indistinguishable bits and bytes, the data is chunked into identifiable discrete elements of information. This technology enables you to store and reuse the information efficiently, share it with many users, and maintain it in a database. This white paper provides an introduction to existing SGML technology, its advantages and benefits, as well as an overview of some related standards and how they fit into an overall approach to managing information. We also define some of the terminology and acronyms to familiarize you with the language associated with SGML. While SGML is a fairly recent technology, the use of markup in computer-based documents has existed for a while. Let's first look at earlier markup schemes that led to SGML. Markup is everything in a document that is not content. Markup originally referred to the handwritten notations that a designer would add to typewritten text; these notations contained instructions to a typesetter about how to lay out the copy and what typeface to use. This kind of markup is known as procedural markup. Most electronic publishing systems today, such as word processing software and desktop publishing software, use procedural markup. Procedural markup is typically unique to a specific software package such as Microsoft Word and Quark XPress. Each has its own set of markup codes that make sense only to itself. This markup usually takes the form of formatting codes that are mixed in with the text of the document. Procedural markup codes apply to a single way of presenting the information, such as a printed page, and provide no capability to define appearance for other media, such as CD-ROM and Internet. Descriptive markup, also known as generic markup, describes the purpose of the text in a document, rather than its physical appearance on the page. The basic concept of descriptive markup is that the content of a document should remain separate from its style. Descriptive markup is based on the structure or content of a document and identifies elements accordingly; such as a chapter, a section, or a table of contents; using notations that describe what the element is, not how it appears. By separating presentation information (i.e., style) from the structure and content, descriptive markup allows for multiple presentations of the same information. For example, you can publish on paper, on-line, on CD-ROM and on the &www; (Internet), all from the same set of source files with descriptive markup. Producers of technical documentation increasingly prefer descriptive markup over procedural markup. Procedural markup is tedious and expensive; authors can spend 15% to 50% of their time on the appearance of each page. If style guidelines change, or if you need to present the same information in a different format, massive re-formatting is usually required. When a company changes software or hardware systems, enormous data translation tasks arise, often resulting in errors. Because procedural markup is tied to one final printed product, you cannot change formats easily. Interchanging documents based on procedural markup works easily only if both parties have the same hardware and software system. The Standard Generalized Markup Language, or SGML, is an international standard (ISO 8879) published in 1986. SGML prescribes a standard format for embedding descriptive markup within a document. More importantly, and crucial to its real value and power, SGML also specifies a standard method for describing the structure of a document. In other words, SGML allows you to set up structural rules for each type of document you produce. SGML ensures that each element, which is labeled with descriptive markup such as chapter, title, and paragraph, fits in the logical, predictable structure of your document type. SGML supports an infinite variety of document structures. Users typically create a different document structure for each category of information they produce: information bulletins, technical manuals, parts catalogs, design specifications, reports, letters and memos. SGML allows you to create documents that are independent of any specific hardware or software. Since SGML documents conform to an international standard, they are portable. You can exchange them seamlessly with users who have different systems. The world of photography demonstrates the power of standards: SGML is to documents as standardized film speed is to cameras. Today you can purchase a roll of film marked ISO 100, put the film in your camera, set the camera's film speed to 100 (which many cameras do automatically), and you're ready to shoot. You don't have to worry that the brand of film is not compatible with your particular make of camera. The film and camera manufacturing industries; through the International Organization for Standardization (ISO) and American Standards Association (ASA); have agreed on standards for film speeds. Many industries plan to use SGML so that their documents work as easily on different computers as film works in different cameras. To understand SGML we must look at the three layers of a typical document: structure, content, and style. SGML separates these three aspects, but deals mainly with the relationship between structure and content. At the heart of an SGML application is a file called the DTD, or Document Type Definition. The DTD sets up the structure of a document, much like a database schema describes the types of information it handles. A DTD provides a framework for the types of elements (such as chapters and chapter headings, sections, and topics) that constitute a document. A DTD also specifies rules for the relationships between elements; for example, a chapter heading must be the first element after the start of a chapter; or each list must contain at least two items. These rules, which the DTD defines, help ensure that documents have a consistent, logical structure. A DTD accompanies an SGML document wherever it goes. A document instance is a document whose content has been tagged in conformance with a particular DTD. Content is the information itself: content includes titles, paragraphs, lists, tables, graphics, and audio. The method for identifying the content's position within the DTD structure is called tagging. Creating an SGML document involves inserting tags around content. These tags mark the beginning and end of each part of the structure and identify the type of contents they enclose. In the following example, par indicates the start of a paragraph, and par indicates the end of the paragraph: <par>Paragraphcontent.</par> You can nest elements within other elements; in the following example, the paragraph (par) is an element within the topic (topic): <topic><par>Content.</par></topic> The structure of a particular document is revealed by the nesting of tags: <section><subhead>Content</subhead> <par>Content is the information itself.</par></section> Fortunately, human beings usually don't have to deal with manually typing in tags and checking to make sure all the tags are there. Some SGML-based authoring software programs make it easy to enter tags by clicking on pull-down menus that guide you by listing only those tags that are valid at the cursor's current position in the document. These programs rely on a software module called a parser that verifies that the document follows the rules of the DTD. (The parser also verifies that the DTD itself is structurally correct.) The following illustration shows how an SGML-based authoring program would display the tags for the previous ASCII example: SGML itself has nothing to do with setting standards for style, so most systems still rely on proprietary methods of setting style. It is the style that determines the final appearance of the document information. Some efforts are being made to develop standards-based style sheets; two of these efforts have resulted in the mature OS standard and the still unreleased DSSSL standard. The U.S. Department of Defense CALS initiative developed its own style standard, known as the Output Specification (OS). The OS is in the form of a particular DTD that allows the user to create a Formatting Output Specification Instance, or FOSI (usually pronounced fossy), that is well suited to both print and electronic output. A FOSI is essentially a powerful style sheet that specifies the formatting for each tag in a DTD. With the FOSI, the document, and the DTD, you have a complete interchange package for printed documents that maintains its format and style as it is interchanged among systems. In early 1995, an ISO committee released a draft of the Document Style Semantics and Specification Language (DSSSL), which is on its way to becoming an international standard for presenting SGML-based documents. Official release is expected later this year. The complete DSSSL standard covers a broad scope, so subsets are being developed to handle varying levels of functionality. A subset whose functionality is approximately equivalent to FOSIs is expected, and work on tools to convert FOSIs to and from DSSSL is under way. Many military contracts currently require FOSIs, and many non-defense firms have also embraced the Department of Defense's OS standard because it's a mature and supported standard. It is expected that both DSSSL and FOSIs will remain important standards for the foreseeable future. SGML has become mainstream technology that you can use with confidence. Your adoption of SGML will allow your organization to gain the maximum value from your generation and use of information: A structured approach to documents helps writers organize the information as they are creating it, and keeps content separate from style. This separation enables you to set up centrally-controlled style guidelines, so authors can focus on generating the content rather than adjusting each document's appearance. That change alone can as much as double your authors' productivity. You can also improve efficiency by keeping a central information base so that authors don't have to recreate the same information in order to use it. This also ensures that the most current information is made available to all. And, a single update to the information base ensures that all documents created from that information base will automatically be updated. A printed document is just one of many possible products from SGML-based information. For example, a technical publications group can use tags to identify a procedure as a sequence of steps. In this case, you identify the beginning and end of the procedure, and each step within the procedure. The same procedure can now appear in several forms: maintenance and operational manuals, on-line technical manuals, training guides, etc. More importantly, since the tags are machine-readable, the computer can manage and maintain the many different uses of the same single source of information, so no re-keying is required to produce this information in new document formats. SGML is a simple, standard file format with an indefinite shelf life; you'll never again have to convert your documents when a hardware or software system becomes obsolete. Once you setup your SGML information base, the information will always be available, because it carries everything needed to create a document. So even when your hardware or software becomes obsolete, your information remains usable, portable, and available. Defining a document's structure helps ensure that the right information is in the right place, which improves the organization of your information. Because SGML eliminates the need for data conversion when it passes across systems, you reduce the risk of losing information by filtering data from one format to another. With SGML, you can define and manipulate information elements at any level of detail. A tagged element can have attributes that provide characteristics or properties about the element. This attribute information is useful for managing and manipulating the information elements. For example, an ID (identifier) attribute can uniquely identify a single paragraph, a whole section, a legal notice, an illustration, a task, or any element that you may want to use repeatedly. The following example shows a paragraph with an ID attribute: <para id=431>Content.</para> By simply referencing the ID, you can include this information into your document in as many places as you need. This eliminates re-typing and ensures that the information is identical in every instance. Plus, the IDs you set are machine readable so that the computer can find and link related information. This allows you to use IDs for a variety of information management controls. These controls can help you: Manage the security of information by allowing only certain people to view or change information with selected IDs. Automate the information flow; for example, updating the data in one place can trigger the update of the same information in other places within the same document and in other documents. Since SGML is aware of the individual components of a document, you can easily build entirely new documents out of existing information. This capability enables users to share the latest information without duplicating it. An example of this might be a standard legal notice or copyright statement appearing in documents throughout a company. The legal department maintains this module of information, updating it on occasion. A single tag in your document can pull in the current legal notice each time you access or output your document, eliminating needless duplication of information and ensuring the accuracy of your information. Today, information networks proliferate where different computers, operating systems, and applications must share information. In these sort of networks, portability becomes the key in making sure all who need it can access the information. Thanks to the hardware and software independence of SGML, you can easily exchange SGML documents among different environments. The information you create today may be used a year from now in ways you haven't yet anticipated. Just last year, the need to publish on the &www; did not even exist! The spectacular growth of the Web serves as dramatic proof that we simply cannot anticipate all the purposes for which our information may eventually be used. SGML permits you to use your information for applications beyond traditional publishing. For example: &www; pages information databases diagnostic/expert systems electronic mail hypermedia and hypertext documents database publishing CD-ROM publishing Interactive Electronic Technical Manuals (IETMs) electronic review In the life cycle of a product, the cost of gathering, producing, and maintaining the necessary technical information can exceed the initial hardware cost. For many industries, technical information is part of a deliverable product, or a product in itself. Any industry whose product line is heavily dependent on information can benefit from SGML. In evaluating how SGML can help your organization, you may wish to consider some strategic business issues to help in your information management plan. A strategic approach should prompt you to examine your current information needs and your current document management methodology. Some questions to consider include: Does your information require a long life-span? (For example, technical information related to airplanes often needs to be maintained for over 20 years.) Do you need to exchange documents across mixed hardware environments? Do you need to produce large documents with a disciplined structure? Do your documents contain information common to other documents within a department, across corporate divisions, or even across separate organizations? Do you have information that's used for different purposes? (For example, a part number may appear in a maintenance manual as well as a parts inventory database.) Does your information change frequently and get used often? Do you produce information that needs to comply to industry or company guidelines? By examining your requirements, you can evaluate how SGML fits into your information management strategy. Standardizing on SGML doesn't mean you need to use it for all documents; SGML is most useful for documents with a definable structure. Since SGML handles documents as collections of distinguishable data elements, it is useful to think in terms of modules of information, rather than complete printed documents. SGML is most useful as a tool in an integrated information management strategy. Making such a strategic choice and planning the implementation should be decided by a company's high-level management. There will be initial implementation costs in moving to SGML. But the payback comes from benefits that accrue over time and enhance your investment in information. Any organization that exchanges information between systems, applications, departments, and companies will realize these benefits. By design, SGML applications are meant to be customized. Just as there's no out-of-box database application that can serve all the needs of an organization, there are no one-size-fits-all SGML application. Since each organization's information requirements are different, there are many DTDs. More organizations are also looking at industry-wide information needs and developing standards for handling that information. A number of products on the market handle SGML to some degree. But not all products handle all the features of the SGML standard. The sections that follow describe some basic requirements. An invaluable feature in an SGML system is real-time, interactive SGML validation. This feature allows the software to provide context-sensitive editing assistance based on the cursor's current position in the document. For example, if the cursor is immediately after the beginning tag for a section, and all sections must have a section heading, the software allows you to insert only a section heading tag. This feature ensures that the author does the correct tagging at all times which ensures that the author creates a valid SGML document the first time. By contrast, systems that use batch parsing allow authors to insert tags and text without checking each action against the DTD. In this approach, authors create documents in one format, then filter parts of the document into SGML, and then run the SGML through a validating parser. When the parser finds errors, the author must correct the original document, then filter and parse the changes again. The author must repeat this cycle until the entire document parses successfully. This approach adds steps to the publishing process that add no value. Time saved by authoring in a familiar format is lost in the filtering and validating process. A system that creates native SGML information eliminates the costly, time-consuming, and often error-prone process of retrofitting documents into valid SGML. If your authoring software merely produces SGML as output, then your information is still tied to a proprietary format, and still at the mercy of software and hardware obsolescence. A publishing system that uses SGML as its native file format allows your information to remain accessible and usable regardless of hardware and software changes. If you need your information to remain accessible as you grow into new systems and new technologies then using a native SGML file format provides a distinct advantage over a system that filters the data into SGML. Here's an acid test to identify a real SGML system: can the software accept any SGML document, display that document, and then save that document, leaving it unchanged? To be fully usable, a good SGML product allows you to create a variety of new document types in addition to accepting existing DTDs used in some industries. This feature is sometimes called the ability to handle arbitrary or user-defined DTDs. With arbitrary DTDs you are free to create any document type. The developers of SGML built into the standard a number of features that facilitate automated publishing and document reuse. A fully-featured SGML publishing package should support this functionality. Some of the basic features to look for include: Marked sections. Marked sections let you create multiple versions from a single master document using regions of conditional text that only appear in specified versions. For example, you might want to build a single source document that describes two variations of your product. You simply write the source document with marked sections for the areas that differ. The system can then identify these areas and produce two different versions of your information from the same source file. External file entities. A file entity is simply a pointer to a separate document file. You can use file entities to break a large document into subdocuments. You can also use a file entity to reference frequently repeated boilerplate information such as an electrical caution. Graphic entities. A graphic entity is a pointer to a separate graphic file. Text entities. A text entity is a single tag that represents a common phrase repeated throughout a document. This allows you to reference the tag instead of re-keying the phrase each time you need to use it. Early in its history, the primary adopters of SGML were defense contractors. In the last two years, however, the trickle of commercial users has turned into a torrent. Many leading industrial groups recognize the benefits SGML offers and have adopted it for information management and exchange among their members, and between members and their vendors and customers. Several industries have developed standards for information exchange: AAP The American Association of Publishers developed The American National Standard for Electronic Manuscript Preparation and Markup, a general purpose book DTD for publishers, authors and editors. ATA (airlines) The Air Transport Association, a consortium representing the commercial airline industry, developed several DTDs under the ATA-100 specification. The ATA's European counterpart, AECMA, is also adopting standards based on SGML. ATA (trucking) The Maintenance Council of the American Trucking Association has initiated a task force with the mission of Establishing the Standard for Electronic Service Information. This task force represents large truck manufacturers and fleet operators interested in standardizing the interchange of service information, and they are developing the T2008 DTD, modeled after the SAE's J2008 DTD for automobiles and light trucks. The first release of the standard is expected in 1996. DocBook Founded by ten major producers and consumers of technical documentation for computer systems, the Davenport Group has developed the DocBook DTD for exchanging and delivering computer documentation. Founding members included Novell, O'Reilly & Associates, Fujitsu OSSI, Hewlett-Packard, Digital Equipment Corporation, SCO, Hal Computer Systems, Hitachi Computer Products, SunSoft and Unisys. DoD The U.S. Department of Defense created the Continuous Acquisition and Life-Cycle Support (CALS) initiative (recently renamed from Computer-aided Acquisition and Logistic Support). The next section describes CALS in more detail. Pinnacles Led by Intel, National Semiconductor, Texas Instruments, Phillips, and Hitachi, the Pinnacles Group is developing the Pinnacles Component Information Standard (PCIS) to allow reusability of component data by semiconductor customers and vendors. This data can include descriptions, specifications, physical diagrams, code fragments, behavior models, and other text, tables, graphics, and technical data. SAE The Society of Automotive Engineers is developing the J2008 DTD for electronic interchange of service and diagnostic information. The J2008 Task Force is part of the Vehicle Electronic/Electrical Systems Committee, whose mission is to increase customer satisfaction and lower product life cycle costs by recommending standards that promote more effective diagnosis of vehicle systems. The DTD is expected to be released for approval as a Technical Draft Standard in 1995. After three years, it will be voted upon again to determine if it should become a Recommended Practice. TCIF The Telecommunications Industry Forum is an international association of carriers and major vendors of telecommunications products and services. The TCIF initiative is focused on the re-use of technical information across multiple applications and different environments. Many SGML applications are in commercial use. Other industries moving to SGML include pharmaceuticals, publishing, and manufacturing. Overseas, SGML is gaining wide acceptance. The European Airbus, a consortium of companies in the commercial airline industry in Europe, adopted SGML. Telecommunications, aerospace, manufacturing, and other commercial and military interests throughout Europe are also using SGML. CALS stands for Continuous Acquisition and Life-Cycle Support (recently renamed from Computer-aided Acquisition and Logistic Support). It is a large-scale, long-term information management project initiated by the U.S. Department of Defense (DoD). Since the DoD receives goods and services from a wide range of suppliers, contractors and subcontractors, it constantly handles massive quantities of technical information. Today's weapon systems are technologically complex and can have a life span of 20 years or more. As a result, the amount of technical data needed to support and maintain these systems is overwhelming. The CALS standards that apply to maintaining technical information include: MIL-STD-1840: The Automated Interchange of Technical Information: this is the umbrella standard specifying overall guidelines for electronic data storage and exchange of CALS documents on magnetic tape. MIL-M-28001: SGML (Standard Generalized Markup Language) for exchanging text. MIL-D-28000 IGES (Initial Graphics Exchange Specification) an object-oriented format for technical drawings. MIL-R-28002 CCITT Group 4 (International Consultative Committee on Telephony and Telegraphy) for raster images. MIL-D-28003 CGM (Computer Graphics Metafile) for object-oriented graphics. Here are a few resources for more information on SGML. The Graphic Communications Association (GCA) was instrumental in the development of SGML. The GCA provides conferences, tutorials, newsletters, and publication sales for both members and non-members.Graphic Communications Association 100 Daingerfield Road Alexandria, Virginia 22314-2804 USA +1 703.519.8160 SGML Open is a non-profit, international consortium of providers of SGML products and services dedicated to accelerating the further adoption, application, and implementation of SGML.SGML Open 910 Beaver Grade Road, #3008 Coraopolis, Pennsylvania 15108 USA +1 412.264.4258 ArborText also offers a range of introductory to advanced level SGML training courses, including DTD and FOSI training. For further information on ArborText's training services, schedules, and course descriptions, please contact ATI's Training Team at +1 313.996.3566. Books on SGML SGML: An Author's Guide to the Standard Generalized Markup Language, Martin Bryan, Addison-Wesley, 1988, ISBN 0-201-17537-5 The SGML Handbook, Charles Goldfarb, Oxford University Press, 1990, ISBN 0-19-863737-9 Practical SGML, Eric van Herwijnen, Kluwer Academic Publishers, 1994, ISBN 0-7923-9434-8 ASCII (American Standard Code for Information Interchange) This standard character encoding scheme is used extensively in data transmission. ANSI (American National Standards Institute) This group is the U.S. member organization that belongs to the ISO, the International Organization for Standardization. attribute An attribute provides more information about an element such as classification level, unique reference identifiers, or formatting information. CCITT Group 4 (International Consultative Committee on Telegraphy and Telephony) This CALS standard for raster graphics incorporates tiling, which divides a large image into smaller tiles. You can exchange graphic files in CCITT/4 format in a compressed state so they take up much less file space. CITIS (Contractor Integrated Technical Information Service) As part of CALS Phase II, CITIS is a draft functional specification for services. DoD acquisition managers designed CITIS as a plan to gain access to product-related digital technical information. CGM (Computer Graphics Metafile) CGM is one of the CALS standard formats for representing 2-D technical illustrations. CGM is an object-oriented graphic format. DSSSL (Document Style Semantics and Specification Language) This draft international standard (DIS 10179) applies to the specification of processing information for SGML documents. DSSSL is expected to became an international standard. DTD (Document Type Definition) A DTD is the formal definition of the elements, structures, and rules for marking up a given type of SGML document. You can store a DTD at the beginning of a document or externally in a separate file. EDI (Electronic Data Interchange) This is a set of computer interchange standards for business documents such as invoices, bills, and purchase orders. element An element is a piece of data within a document that may contain either text or other subelements such as a paragraph, a chapter, and so on. element declaration A statement in the DTD defining an element and declaring the order in which it may appear in the document and what other elements it may include. entity An entity is a self-contained piece of data that can be referenced as a unit. You can refer to an entity by a symbolic name in the DTD or the document. An entity can be a string of characters, a symbol character (unavailable on a standard keyboard), a separate text file, or a separate graphic file. entity declaration A statement in the DTD or document that assigns an SGML name to an entity so you can reference it. FOSI (Formatting Output Specification Instance) A FOSI is used for formatting SGML documents for printing and other outputs. It is a separate file that contains formatting information for each element in a document. HTML (HyperText Markup Language) This is the format of files published on the &www;. HTML is an application of SGML; to author in HTML using SGML-based authoring software, you simply need the HTML DTD. IGES (Initial Graphics Exchange Specification) The IGES standard for engineering, product design, and manufacturing drawings is one of the CALS standard graphics formats. Internet The Internet is a worldwide communications network originally developed by the U.S. Department of Defense as a distributed system with no single point of failure. The Internet has seen an explosion in commercial use since the development of easy-to-use software for accessing the Internet. ISO (International Organization for Standardization) The ISO is an industry-supported organization that establishes worldwide standards for everything from data interchange formats to film speed specifications. markup Markup is anything added to the content of the document that describes the text. parser A parser is a specialized software program that recognizes SGML markup in a document. A parser that reads a DTD and checks and reports on markup errors is a validating SGML parser. A parser can be built into an SGML editor to prevent incorrect tagging and to check whether a document contains all the required elements. PDES/STEP (Product Data Exchange Standard/Standard for the Exchange of Product Model Data). PDES/STEP are standards under development for communicating a complete product model with sufficient information content that advanced CAD/CAM applications can interpret. PDES is under development as a national standard and STEP is under development as its international counterpart. tag In the world of SGML, a tag is a marker embedded in a document that indicates the purpose or function of the element. Each element has a beginning tag and an end tag. &www; Often referred to as WWW or the Web, this usually refers to information available on the Internet that can be easily accessed with software usually called a browser. Organizations publish their information on the Web in a format known as HTML; this information is usually referred to as their home page or web site.