— BO WEEHNAPPLIČATION DEVELOPMENT /AWGUST 14, 1989 pe € VI —————————OEOEEOT APPLJED INTELLIGENCE SA A's Presentation, Dialog Interfaces Ease Programming This is Part 6 of a series of articles om IBM s Systems Applicdtion Ar- chitecture (SAA). The in- troduction of in- tegrated, comput- ing environ- ments such as SAA will have a major impact on the software technologies of the '90s. A chief benefit of integrated comput- ing environments such as IBM's SAA is the provision of a standard user inter- face that makes all applications appear to behave in a consistent and familiar manner. The SAA component that gov- erns the user interface is called Com- mon User Access (CUA), which is based on the interface developed at Xerox Palo Alto Research Laboratories and popularized by the Apple Computer Inc. Macintosh. CUA supports texvoniy funetions ap- propriate for a non-programmable ter- minal and graphically oriented functions designed for a programmable worksta- tion. With a workstation, the user has windows open for different applications or different parts of the same applica- tion. Menu bars with associated pull- down menus provide access to the vari- ous functions. Users are in complete control of the interface. A mouse can be used to select a window or to move to another part of the screen. Users might open a new win- dow or close an old one. Seroll bars might be used to access material that is too large to fit within the view dis- played in the window. This type of graphically oriented in- ' terface has proven comfortable for users and is casy to learn. 1t is based on the metaphor of (he desktop: 'The user se- Jects objecis on the on-sereen desktop and manipulates them in a consistent, manner. Consistency: means that seroll- bar operation and window manipulation be the same for all applications. The Mmenus and multiple windows vastly re- duce —and can even eliminate—the need for the user to learn any command syntax or to sludy complex documenta- ion, There are no difi fering "modes" of operation with eonfusing behaviors. The User can move anywhere in the inter- face at any time. č Although this bpe sirable, programmers Only a new set of tools but also a h Pletely different. manner of Pot zde koline applications, The event. nterfaces reguired to respond me interaction are not only ani Most. programmers, hard to write, vale lom IBM is attacking the problem with Wo programming (s PR deei $ facilities for building The Presentation of interface is de- e interface is £rammer's (pol for building a neče driven interface, [1 is a very 'erful facility and is difficult to poe The Dialog interface is a high-leve] need to master not hat provides an easy way to imple- aH oobnitiniven interfaces for certain classes of applications. For example, the Dialog interface makes it easy to devel: op transaction-processing applications that give the user filled-in forms for gathering data to maintain a database. It could not be used for applications that reguire more intensive user interac- tion, such as text processing, or for ap- plications that reguire high-speed graph- ic interaction. The main strength of Presentation Manager's interface is the freedom it gives the user to control the interface to applications. The interaction might be ap- plication-specific, such as entering re- A Single Window to SAA's World iiterface Provides Corinon User Aceess to Ali SAA Applieationis TITLE BaR FUNCTion ETI ŠCROLI Ba5 Aetiokrgag ———— HM kev AREA cult to decide whether to make an in- vestment in training to use Presentation Manager. Although the benefits to users are demonstrable, it is not clear if these benefits are worth the cost in training and development. : Not only is it difficult to build appli- cations with Presentation Manager, but due to the fundamental reorganization of application logic, converting. existing applications to a Presentation interface may also be difficult. The real power of the Presentation interface is available only in C, so programmers must learn that language as well. | The difficulties inherent in converting to a Presentation interface are not ap- pealing to large, conventional COBOL programming organizations; however, for those organizations willing to make the commitment, there are tremendous advantages. The easiest, way to bring this new technology into conventional organiza- tions is through the use of higher-level tools. A layer of development software must be built that lets programmers concentrate on the application logic, not the user interface. The tools should automatically build ihe interface for the application. Dialog Interface: A First Step The Dialog interface, built atop the Presentation interface, is a first step in that direction. As with all high-level pro- gramming tools, it automates the devel- opment. process for a restricted class of applications. The programmer specifies, in a non- procedural manner. ihe attributes of a dialogue, such as menu entries and fields in 4 form. The dialogues are com- piled separately. The programmer sim- ply calis them when needed. The Dialog Manager run-time system handles all of the top-level control necessary for deliv- ering an event-driven user interface, The programmer iises a conventional development style (hat maintains pro- gram funetion as the highest organizing principle. When communication with the User is reguired, the Dialog Manager is a dialogue with the user. The dialogues are scattered throughout the application. Presentation Manager reguires that : user 1/0 be the highest organizing princi: ple, with subservient application func- tions. In conventional applications, the function is considered to be the highest organizing principle. h When function comes first, the user is at the mercy of the application and is forced to respond with a specialized command syntax that is unigue to the program. The user can do only what. is allowed by the application at that point. In general, the user often develops a helpless, anti-computer, frustrated feel. ing. [5] SCROLL BAR som Avakan — called with the name of the dialogue. Use of the Dialog Manager still re- ; 7 4uires some redesign of an application. The main strength of PM's interface is the freedo it gi A conventional full-sereen a lication ni, IN GWES . ures the use ip remi Pirš the interfi te ena ions. The PE ne user to (lip from panel to action might be applicat guested information, or it might. occur system level, such as when movi je dows or initiating another application. The main difficulty in developing an am controlled by Presentation anager is providing the intellig« deal with all possible user Rodote sa Using the Presentation interface, the highest. level of organization in the user- interface program is the dispateh sa ugina certain user actions and appropriate s na Š modules for is in sharp contrast, to com k al applications that are organized by ag plication function. When a function has to communicate with the user, it initiates ion-specific or at a system level. Posa roka panel. ln a windowing environment, this is no longer necessary. An application that was originally