Encyclopedia of Computer Science and Technology

160 document modelSociety for Technical Communication. Available online. URL:http://www.stc.org/. Accessed July 9, 2007.document modelMost early developers and users of desktop computing systemsthought in terms of application programs rather thanfocusing on the documents or other products being createdwith them. From the application point of view, filesare opened or created, content (text or graphics) is created,and the file is then saved. There is no connection betweenthe files except in the mind of the user. The dominant wordprocessors of the 1980s (such as WordStar and WordPerfect)were designed as replacements for the typewriter andemphasized the efficient creation of text (see word processing).Users who wanted to work with other types ofinformation had to run completely separate applications,such as dBase for databases or Lotus 1-2-3 for spreadsheets.Working with graphics images (to the extent it was possiblewith early PCs) required still other programs.This “application-centric” way of thinking suited programdevelopers at a time when most computer systems(such as those running MS-DOS) could run only one programat a time. But increasing processor power, memory,and graphics display capabilities during the late 1980s madeit possible to create an operating system such as MicrosoftWindows that could display text fonts and formatting,graphics and other content in the same window, and runseveral different program windows at the same time (seemultitasking). In turn, this made it possible to present amodel that was more in keeping with the way people hadworked in the precomputer era.In the new “document model,” instead of thinking interms of individual application programs working withfiles, users could think in terms of creating documents.A document (such as a brochure or report) could containformatted text, graphics, and data brought in from databaseor spreadsheet programs. This meant that in the course ofworking with a document users would actually be invokingthe services of several programs: a word processor, graphicseditor, database, spreadsheet, and perhaps others. To theuser, however, the focus would be on a screen “desktop” onwhich would be arranged documents (or projects), not onthe process of running individual programs and loadingfiles.Implementing the Document ModelThere are two basic approaches to maintaining documents.One is to create large programs that provide all of the featuresneeded, including word processing, graphics, and datamanagement (see application suite). While such tightintegration can (ideally at least) create a seamless workingenvironment with a consistent user interface, it lacksflexibility. If a user needs capabilities not included in thesuite (such as, perhaps the ability to create an HTML versionof the document for the Web), one of two cumbersomeprocedures would have to be followed. Either the operatingsystem’s “cut and paste” facilities might be used to copydata from another application into the document (possiblywith formatting or other information lost in the process),or possibly the document could be saved in a file formatthat could be read by the program that was to provide theadditional functionality (again with the possibility of losingsomething in the translation).Linking and EmbeddingA more sophisticated approach is to create a protocol thatapplications could use to call upon one another’s services.The Windows COM (Component Object Model) uses a technologyformerly called OLE (Object Linking and Embedding).Using this facility, someone working on a documentin Microsoft Word could “embed” another object such asan Excel spreadsheet or an Access database into the currentdocument (which becomes the container). When theuser double-clicks on the embedded object, the appropriateapplication is launched automatically, and the user sees thescreen menus and controls from that application instead ofthose in Word. (One can also think of Word in this examplebeing the client and Excel or Access as the server—see client-servercomputing). All work done with the embeddedobject is automatically updated by the server applicationand everything is stored in the same document file. Alternatively,an application may be linked rather than embedded.In that case, the container document simply containsa pointer to the file in the other application. Wheneverthat file is changed, all documents that are linked to it areupdated. Object embedding thus preserves a document-centricapproach but works with any applications that supportthat facility, regardless of vendor. The Macintosh operatingsystem offers a similar facility. Apple and IBM attemptedunsuccessfully to create a competing standard called Open-Doc. This should not be confused with the more recentOpen Document standard from the popular open-sourceapplication Open Office. Meanwhile Microsoft’s COM, graduallyintroduced during the later 1990s, has been largelysuperseded by .NET (see Microsoft .NET). This reflectsa shift in emphasis from a document model (within a sin-The Document Object Model (DOM) treats a Web page as an objectthat can be manipulated using a variety of scripting languages.