SYSTEMS DESIGN

Learning objectives Identify and differentiate between several systems design strategies. Describe the design phase tasks in terms of a computer- based solution for an in-house development project. Describe the interface design Describe the input design Describe the output design Describe the database design

Chapter Map

System Design Information systems design is defined as those tasks that focus on the specification of a detailed computer-based solution. It is also called physical design. Thus, whereas systems analysis placed emphasis on the business problem, systems design places emphasis on the technical or implementation concerns of the system.

Model-driven development techniques emphasize the drawing of models to help visualize and analyze problems, define business requirements, and design information systems. –Modern structured design –Information engineering –Object-oriented –Prototyping Joint application development (JAD) Rapid application development (RAD) System Design Approaches

Output Design

Types of outputs Internal outputs External outputs Turnaround outputs

Internal Outputs Internal outputs are intended for the internal system owners and system users within an organization. –Detailed reports present information with little or no filtering. –Summary reports categorize information for managers who do not want to wade through details. Increasingly presented in graphical formats using charts. –Exception reports filter detailed information before presenting it.

Detailed Report

Summary Report

Exception Report

External Outputs External outputs leave an organization.They are intended for customers, suppliers, partners, or regulatory agencies. Examples: Account statements, invoices, course schedule, Airline tickets, boarding passes, telephone bills and purchase orders.

External Document

Turnaround Outputs Turnaround documents are external outputs that eventually re-enter the system as inputs. Most “bills” and invoices include a stub to be returned by the customer with payment.

Turnaround Outputs

Output Implementation Methods Printed output –Tabular output presents information in columns. Screen output –Graphic output is the use of pictorial charts to convey information in ways that demonstrate trends and relationships that cannot be easily seen in tabular formats. Point-of-sale terminals Multimedia Graphics, sound, pictures and animation

Chart Types Sample Line Chart Area Chart Bar Chart Column Chart for summarizing and showing the change in data over Selection Criteria Line charts show one or more series of data over a period of time. They are useful for summarizing and showing data at regular intervals. Each line represents one series or category of data. Area charts are similar to line charts except that the focus is on the area under the line. That area is useful time. Each line represents one series or category of data. Bar charts are useful for comparing series or categories of data. Each bar represents one series or category of data. Column charts are similar to bar charts except that the bars are vertical. Also, a series of column charts may be used to compare the same categories at different times or time intervals. Each bar represents one series or category of data.

Output Design Guidelines Outputs should be simple to read and interpret. –Every output must have a title. –Every output should time and date stamped. –Reports and screens should include headings. –Fields and columns should be clearly labeled. –Reports should include legends for all abbreviations. –Information should never have to be manually edited. –Information should be balanced across the page or screen. –Provide for easy navigation within information. –Avoid computer jargon and most error messages. The timing of outputs is important. The distribution of (or access to) outputs must be sufficient to assist all relevant users. Outputs must be acceptable to the system users who will receive them.

INPUT DESIGN

Input Implementation Methods Keyboard Mouse Touch Screen point-of-sale terminals –Bar codes

Bad Flow in a Form

Good Flow in a Form

GUI Components (or Controls) Common GUI controls (for both Windows and Web interfaces) –Text boxes –Radio buttons –Check boxes –List boxes –Drop down lists –Combination boxes –Spin boxes –Buttons –Hyperlinks (yes, also for Windows applications—see Quicken 2000) Advanced controls (mostly for Windows interfaces) –Drop down calendars –Slider edit controls –Masked edit controls –Ellipsis controls –Alternate numerical spinners –Check list boxes –Check tree boxes

Common GUI Components

Input Prototype for Data Maintenance

Input Prototype for Transaction

Input Prototype for Data Maintenance

USER INTERFACE DESIGN

System User Classifications An expert user is an experienced computer user who will spend considerable time using specific application programs. In the mainframe computing era, this was called a dedicated user. The novice user (sometimes called a casual user) is a less experienced computer user who will generally use a computer on a less frequent, or even occasional, basis.

Human Factors (Interface Problems) These problems result in confusion, panic, frustration, boredom, misuse, abandonment, and other undesirable consequences. –Excessive use of computer jargon and acronyms –Inability to distinguish between alternative actions (“what do I do next?”) –Inconsistent problem-solving approaches –Design inconsistency

Commandments of User Interface Design Understand your users and their tasks. Involve the user in interface design. Test the system on actual users. Practice iterative design.

Human Engineering Guidelines 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.

Human Engineering Guidelines The screen should be formatted so that the various types of information, instructions, and messages always appear in the same general display area. Messages, instructions, or information should be displayed long enough to allow the system user to read them. Anticipate the errors users might make. With respect to errors, a user should not be allowed to proceed without correcting an error. If the user does something that could be disastrous, the keyboard should be locked to prevent any further input, and an instruction to call the analyst or technical support should be displayed.

Common Approaches to Showing the Display Area Paging displays a complete screen of characters at a time. The complete display area is known as a page (or screen). The page is replaced on demand by the next or previous page, much like turning the pages of a book. Scrolling moves the displayed information up or down on the screen, one line at a time. This is similar to the way movie and television credits scroll up the screen at the end of a movie.

Styles or Strategies Used For Designing Graphical User Interfaces Menu-driven interfaces  Pull down and cascading menus  Pop-up menus  Toolbar and iconic menus  Hypertext and hyperlink menus

Pull-Down and Cascading Menus

Pop-Up Menus

Iconic Menus

Authentication Error Screen

Additional User Interface Controls

SoundStage Main Menu

SoundStage Options and Preferences Screen

SoundStage Report Customization dialogue Screen