Copyright Irwin/McGraw-Hill 1998 1 User Interface Design and Prototyping Prepared by Kevin C....

Prepared by Kevin C. Dittman for

Systems Analysis & Design Methods 4ed

by J. L. Whitten & L. D. BentleyCopyright Irwin/McGraw-Hill 19981

User Interface Design and Prototyping

Introduction

The chapter will address the following questions: Which features on available terminal and microcomputer displays

can be used for effective user interface design? What are the backgrounds and problems encountered by different

types of terminal and microcomputer users? How do you design and evaluate the human engineering in a user

interface for a typical information system? How do you apply appropriate user interface strategies to an

information system? How do you use a state transition diagram to plan and coordinate a user interface for an information system?

How can prototyping can be used to design a user interface.





Styles of User Interfaces

Introduction User interface design is the specification of a conversation

between the system user and the computer. This conversation generally results in either input or output --

possibly both.






Menu Selection The menu selection strategy of dialogue design presents a list of

alternatives or options to the user. The system user selects the desired alternative or option by keying in the number or letter that is associated with that option. More sophisticated technology allows menu selection by

touching the screen, or selecting menu options with a pen, mouse, cursor keys, or other pointing devices.






Menu Selection Menu Bars:

Menu bars are used to display horizontally across the top of the screen/window a series of choices from which the user can select.

• The choices typically correspond to commands or properties that the user can select or toggle.

• The choices themselves are typically organized from left-to-right on the basis of the frequency that a choice is selected.

Menu bars are used to identify common and frequently used actions that take place in a wide variety of different windows that make up the application.






Menu Selection Menu Bars:

Menu bars advantages:• Always being readily visible to the user

• Consistently located

• Easily selected via the keyboard or mouse Menu bars disadvantages:

• Menu choices are organized for left-to-right scanning.

– Studies have shown that users can more easily browse and select from a list that is vertically arranged.

– To aid in clearly scanning the list, adequate spacing between choices is necessary.





Menu Bar






Menu Selection Pull-Down Menus:

Pull-down menus provide a vertical list of choices to the user. A pull-down menu is made available once the user selects a

choice from a menu bar. The list of choices are typically organized from top-to-bottom

according to the frequency in which they are chosen One special type of pull-down menu is called a tear-off menu.

• With a tear-off menu, the user can select the menu and drag to relocate it elsewhere on the screen.

• The tear-off menu is then available for continual referencing.







Pull-down menu advantages:• Allows the designer to simplify a menu bar that may otherwise

contain too many choices.

– Related set of choices are “grouped” into its own separate list.

• Pull-down menu items can be selected via the keyboard or mouse.







Pull-down menu disadvantages:• The user is not provided with a visual clue that suggests the menu

exists.

• Pull-down menu may obstruct the user’s view of other areas of interest appearing within the body of the screen/window.

• A choice appearing on a pull-down menu may result in yet another list or menu of choices.

– Choices which have a a right-pointing arrow next to the label result in a cascading menu.

– Choices which have an eclipse next to the label result in a dialogue box being displayed that contains commands and properties for the user to complete a task.





Pull-down Menu





Dialogue Box






Menu Selection Cascading Menus:

A cascading menu is a menu that must be requested by the user from another higher-level menu.

The cascading menu’s existence is suggested by the visual clue of a right-pointing arrow appearing next to the higher-level menu choice.

When requested, the menu list will appear to the immediate right (in some cases, to the left) of the selected choice from the higher-level menu.






Menu Selection Cascading Menus:

Cascading menu advantages:• Cascading menus simplify higher-level menus into a smaller set of

related group of choices.

• Vertical arrangement of the choices also makes scanning the choices easier.

Cascading menu disadvantages:• Menu must be requested by the user.

• User may have to traverse several levels of menus to locate and select a desired option.





Cascading Menu





Cascading Menu






Menu Selection Pop-up Menus:

A pop-up menu is a vertical listing of choices that must be requested by the user.

A pop-up menu is requested by clicking the right mouse button.

Unlike pull-down and cascading menus, the pop-up menu’s appearance depends on where the pointer was located when the menu was requested.







Pop-up menu advantages: • Provide a list of options that pertain to a specific object that the

user selected.

– When the cursor is positioned over an object of interest and the right mouse button is clicked, a pop-menu containing commands or properties pertaining to that object appears in the vicinity of the object.

• Allows the user to obtain a list of actions without changing their focus away from the object or work area on the screen.







Pop-up menu disadvantages:• No visual clue that suggests their existence.

• Users must learn about the existence pop-up menus.

• May obstruct portions of the viewing area of interest to the user.










Menu Selection Iconic Menus:

An iconic menu uses graphic representations for menu options.• These types of menus are typically used to present the user with

options that pertain to special functions that can be performed within the application.

Iconic menu advantages:• Easy recognition of options.

– The use of graphic images helps the user to memorize and recognize the functions available within an application.

• The choice presented in the form of an icon also provide a relatively larger selection target than the previously discussed menus.






Menu Selection Iconic Menus:

Iconic menu disadvantages:• May be difficult to find or create meaningful graphic images.

• Not everything can easily be represented as a picture.

• What is a readily identifiable and meaningful picture to one person may not be to the next person.





Iconic Menu






Instruction Sets Instead of menus -- or in addition to menus – applications can be

designed using a dialogue around an instruction set (also called a command language interface). Users must learn the syntax of the instruction set and this

approach is suitable only for dedicated users. There are three types of syntax.

• A form of Structured English can be defined as a set of commands that control the system.

• A mnemonic syntax is built around meaningful abbreviations for all commands.






Instruction Sets There are three types of syntax. (continued)

• Natural language syntax is when the system user enters commands using natural English (either conversational or formal, written English).The system interprets these commands against a known syntax and requests clarification if it doesn't understand what the user wants. As new interpretations become known, the system learns the system user's vocabulary by saving it for future reference.














Question-Answer Dialogues Question-answer dialogue strategy is an style that was primarily

used supplement either menu driven or syntax-driven dialogues. This strategy involves the system asking the system user

questions. The simplest questions involve yes or no answers. This strategy requires that you make sure to consider all

possible correct answers and deal with the actions to be taken if incorrect answers are entered.

Question-answer dialogue is difficult because you must try to consider everything that the system user might do wrong!





Question

Answer






Direct Manipulation Allows direct manipulation of graphical objects appearing on a

screen. This user interface style focuses upon using icons, small graphic

images, to suggest functions to the user. Selecting the icon with a pointing device like a mouse or light pen

executes the function. Icons can work in conjunction with one another.

A pointing device can be used to drag the icon of a file folder (representing a named file) to a trash can icon — intuitively instructing the system to delete (or throw away) the file.









Human Factors for User Interface Design

Introduction System users can be broadly classified as either dedicated or

casual. A dedicated system user is one who will spend considerable

time using specific programs. This user is likely to become more comfortable and familiar with the terminal or PC's operation.

The casual system user may only use a specific program on an occasional basis. This user may never become truly comfortable with the terminal or the program.






General Human Engineering Guidelines Guideline 1: The system user should always be aware of what to

do next. Tell the user what the system expects right now. Tell the user that data has been entered correctly. Tell the user that data has not been entered correctly. Explain to the user the reason for a delay in processing. Tell the user that a task was completed or was not completed.

Guideline 2: The screen should always be formatted so that the various types of information, instructions, and messages always appear in the same general display area.






General Human Engineering Guidelines Guideline 3: Messages, instructions, or information should be

displayed long enough to allow the system user to read them. Guideline 4: Use display attributes sparingly. Guideline 5: Default values for fields and answers to be entered

by the user should be specified. Guideline 6: Anticipate the errors users might make.






Dialogue Tone and Terminology The overall tone and terminology of a dialogue are important and

the session should be user friendly. With respect to the tone of the dialogue, the following guidelines

are offered: Use simple, grammatically correct sentences. Don't be funny or cute! Don't be condescending; that is, don't insult the intelligence of

the system user.






Dialogue Tone and Terminology With respect to the terminology used in the dialogue, the

following guidelines are offered: Don't use computer jargon. Avoid most abbreviations. Use simple terms. Be consistent in your use of terminology.






Dialogue Tone and Terminology With respect to the terminology used in the dialogue, the

following guidelines are offered: (continued) Instructions should be carefully phrased, and appropriate

action verbs should be used. • The following recommendations should prove helpful:

– Try SELECT instead of PICK when referring to a list of options.

– Use TYPE, not ENTER, to request the user to input specific data or instructions.

– Use PRESS, not HIT or DEPRESS, to refer to keyboard actions.

– When referring to the cursor, use the term POSITION THE CURSOR, not POINT THE CURSOR.





Display Features That Affect User Interface Design

Display Area The size of the display area is critical to user interface design. For terminal displays, the two most common display areas are 25

(lines) by 80 (columns) and 25 by 132. For microcomputer and workstation display monitors, display size

is measured in pixels. The greater the number of pixels, the more information can be

displayed. Pixel display areas are specified in width by height.






Character Sets and Graphics Every display uses a predefined character set. Most displays use the common ASCII character set. Some displays allow the programmer to supplement or replace the

predefined character set. Most displays today offer graphics capabilities.

Graphics capabilities must be supported by graphics controllers and software that allow the programmer to take advantage of the graphics capabilities.

Graphics-based displays may support a virtually unlimited character set.






Paging and Scrolling The manner in which the display area is shown to the user is

controlled by both the technical capabilities of the display and the software capabilities of the computer system. Paging displays a complete screen of characters at a time. The

complete display area is known as a page (also called a screen or frame). The page is replaced on demand by the next or previous page.

Scrolling moves the displayed characters up or down, one line at a time.






Display Properties Most displays in use today provide a wide variety of display

properties that may be manipulated to more effectively present data and information.

Display properties are characteristics that change the way in which a character or group of characters is displayed on a screen.






Split-Screen and Windowing Capabilities Split-screen capability is a variation on the windows concept. The display screen, under software control, can be divided into

different areas (called windows). Each window can act independently of the other windows,

using features such as paging, scrolling, display attributes, and color.

Each window can be defined to serve a different purpose. Windows can be resized, moved, and hidden or recalled on user demand.






Keyboards and Function Keys Most modern terminals and monitors are integrated with

keyboards. The number of keys and their layout may vary, but most

keyboards contain special keys called function keys.• Function keys (usually labeled F1, F2, and so on) can be used to

implement certain common, repetitive operations in a user interface (for example, START, HELP, PAGE UP, PAGE DOWN, EXIT). These keys can be programmed to perform common functions.

Function keys should be used consistently. • A system's programs should consistently use the same function

keys for the same purposes.






Pointer Options There are many selection options, such as touch-sensitive screens,

voice recognition, and pointers. The most common pointer is the mouse.

• A mouse is a small hand-sized device that sits on a flat surface near the terminal. It has a small roller ball on the underside. As you move the mouse on the flat surface, it causes the pointer to move across the screen. Buttons on the mouse allow you to select objects or commands to which the cursor has been moved. Alternatives include trackballs, pens, and trackpoints.





How to Design & Prototype a User Interface

Step 1: Chart the Dialogue A state transition diagram is used to depict the sequence and

variations of screens that can occur when the system user sits at the terminal (PC or workstation). Rectangles are used to represent display screens. The arrows represent the flow of control and triggering event

causing the screen to become active or receive focus. The rectangles only describe what can appear during the

dialogue. The direction of the arrows indicate the order in which these

screens occur.





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1

1

2

2 2

3

4






Step 2: Prototype the Dialogue and User Interface Many screens may have to be designed and prototyped.

Some screens were identified for the purpose of bringing together the application and its input and output screens.

Some screens were identified for the purpose to provide the user some flexibility with customizing the application’s interaction to suit their own preferences.

Other screens may have been identified to deal with system controls such as backup and recovery.

It is through studying the entire collection of screens that you may discover the need to make revisions to some screens.

It is likely that such issues as color, naming consistencies of common buttons and menu options, and other look-and-feel conflicts may need to be resolved.









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Step 3: Obtain User Feedback Exercising (or testing) the user interface is a key advantage of all

prototyping environments. Exercising (or testing) the user interface means that system

users literally experiment with and test the interface design prior to extensive programming and actual implementation of the working system. Analysts can observe this testing to improve on the design.

In the absence of prototyping tools, the analyst should at least simulate the dialogue by walking through the screen sketches with system users.





Summary

Introduction Styles of User Interfaces How to Design & Prototype a User

Interface

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