The World’s Simplest IS

1

ReceiveData

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AnotherEntity

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D1 Data Store

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A Slightly More Realistic IS

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Entity F

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What it usually looks like

Entity A

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Where to start?• Two schools of thought:

– evolution: start with current system and identify changes

– revolution: start from scratch

• Either way, there are two approaches to modeling:– data-driven - identify relevant data first

– process-driven - identify relevant functions first

System Modeling Approaches

Data-driven:

• Develop ER diagram

• Translate to data stores

• Fill in processes between data stores

• Define data flows and external entities

Process-driven:

• Identify major tasks or processes

• Identify the inputs and outputs to the tasks

• Translate to processes and data flows

• Identify data stores and external entities

End Result: a Data Flow Diagram

Data Flow Diagrams

Context diagram

Level 0 diagram

Child diagrams

Physical diagrams

Partitioned physical diagrams

Current diagrams

Proposed diagrams

Analysis

Design

Four parts to a system design

• System architecture

• Interface design

• Database design

• Process design

Elements of the design

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InterfaceSystem Architecture

DatabaseProcess

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Developing the Design Elements• System architecture: set of processes in the Level 0

DFD of the proposed system (functional decomposition of system)

• Database design: derived from the ER diagram and data stores on the DFD

• Interface design: determine form and content of all input and output data flows on DFD, as well as overall interface

• Process (software) design: add logic and timing to all processes on DFD (logic models)

Interface Design

• Inputs and outputs– data flows to and from external entities– data flows into and out of processes that are

manual or not fully automated

• User interaction– how the user communicates with the system– mechanisms for navigation, feedback, control,

security, etc.

I/O Design Issues

• Audience– What tasks are they doing?– What level of detail do they provide or need?– How technology-literate are they?– How much time will they spend with the input

or output?– How often will they provide the input or

generate the output?

Media• For a given input or output, you must decide

whether it should be:– paper or electronic (or something else)

• accessibility of computers to system users

• portability

• expected life

• expected frequency

– on-line or batch • timeliness required

• underlying hardware and support software

Designing Layout

• Consistency is key!

Throughout the system:– use the same colors for the same purposes– use the same highlighting or borders to convey

similar meanings– use terminology and acronyms consistently– put similar pieces of information in the same

location

Designing Layout (cont.)

• Color and highlighting– First of all: CONSISTENCY!– Second: Moderation!– Best combination: black on yellow– Worst combination: red on green– Strong techniques such as blinking and audio

should only be used in the rarest occasions, and then only temporarily

Designing Layout (cont.)

• Bias– Your design outlives you!– Sorting - more attention is given to things listed first– Ranges - make sure they’re the right ones– Graphics:

• color and appropriateness• scale• user training

– User customization - a double-edged sword– User involvement - required

Designing Layout (cont.)

• Use plenty of white space

• Plan for screen and page breaks

• Include administrative information

• Top to bottom, left to right

• Use “Submit” and “Clear” buttons

Input Accuracy and Efficiency• Layout

– top to bottom, left to right– group related items together– separate titles from body from instructions– clear titles and captions– don’t be stingy with white space

• Eliminate typing– checkboxes, pull-down menus, icons– default values

• Checking accuracy– check reasonableness of combinations– predefined acceptable values– check for proper format– check for missing values

Assessing Usability• Can assess an entire system for usability, or just

one form or report• User involvement in usability assessment is

necessary• Some measures:

– learning time– user speed– user accuracy– user’s ability to remember system operation– subjective assessments

Interaction Methods• Command language - necessary on some older

systems, but pretty much outdated• Menus - most common at this point

– drop-down, pop-up

• Forms - good if the interaction consists of specific pieces of information

• Object-based (icons) - intuitive and space-efficient, but can be designed poorly

• Natural language - not there yet

Conventions

• When designing the overall user interface, you must decide on some conventions to be used throughout the system, e.g.:– what different colors mean– what certain symbols mean– navigation mechanisms– terminology– artwork and logos

Navigation

• Always make the next step clear

• Don’t overly restrict the user’s movement

• No dead ends

• Navigation mechanisms should be used consistently

• Let the user know (or choose) consequences of leaving a form

Dialogue Diagrams

• Map out the overall user interaction with the system

• Represents the expected use of the system

• Doesn’t necessarily capture all possible scenarios

• Represents the inputs and outputs and the order in which they will be accessed

Dialogue Diagram Example(Perfect Pizza)

0Main

SystemScreen

1New

CustomerScreen

2,0

2NewOrderScreen3,4,0

3Delivery

Instructions

4,0

4CookOrder

3,0

5Weekly

SalesReport

0

User Feedback• Status

– always let the user know what’s going on– don’t let “no news be good news”

• Prompts – tells the user what is expected of them– convey as much guidance as possible within reason

• Errors and warnings– convey importance– suggest resolutions– be careful of jargon

Providing Help

• Provide different levels of help

• Test a lot under realistic conditions

• Use a variety of terms to help in searching

• Starting point should always be visible

• Navigating help should be simple

Security• Often not considered part of user interface design• Helpful to choose security mechanisms at user interface

design so that the user’s role in security can be integrated into the interface

• Mechanisms:– Views and authorization rules - restrict access according to

who the user is– Authentication schemes - establishes identity of user– Encryption procedures - protects against access from outside

GUIs

• GUI - Graphical User Interface• Allows different parts of user interface to be

active at the same time• Complicates dialogue design• Common components:

– data entry boxes– check boxes– radio buttons– drop-down menus or list boxes– command buttons– message windows– tab control dialog boxes

Special Considerations for Web Interfaces

• Test using different browsers• Use and reuse other sites as examples• Navigation - no dead ends!• Form is not enough• Plan for maintenance• Using a metaphor can be helpful• Use keywords in text• Beware of background patterns• Home page should load quickly