System Messages, Screen Design and Color

Messages need to be informative, screens uncluttered.

Error Messages

In some cases systems, are remembered more for what happens when things go wrong than for when things go right. --- Schneiderman.

Error Message Guidelines

Product.

• Be as specific and precise as possible;
• Be constructive, indicate what need to be done;
• Use a psotive tone, avoid condemnation;
• Choose user-centered phrasing;
• Consider mulitple levels of messages;
• Keep consistent grammatical form, terminology, and abbreviations;
• Keep consisten visual form and placement.

Process

• Establish a message quality control group;
• Include messages in the design phase;
• Place all messages in a file;
• Review messages during the development;
• Attempt to eliminate the need for messages;
• Carry out acceptance tests;
• Collect frequency data for each message;
• Review and revise messages over time.

Avoid anthropomorphic computer talk.

Display Design

Some of the data display guidelines of Smith and Mosier (MITRE Corp.)

• At any stage in a transaction sequence, ensure that whatever data the user needs will be available for display.
• Display data in directly usable form, do not make users convert data.
• For any type of data display maintain consistent format form one display to another.
• Use short, simple sentences.
• Use affirmative statements rather than negative ones.
• Adopt some logical principle for ordering lists; where no other principle exists use alphabetic order.
• Ensure that labels are sufficiently close to their data fields but at least one space away.
• Left justify columns of alphabetic data to assist rapid scanning.
• In multi-paged displays lable each document to show its relation to the others.
• Begin every display with a title or header, describing briefly the contents or purpose of the display; leave at least one blank line between the heading and the contents of the display.
• For size coding a larger symbol should be at least 1.5 times the height of the next smaller sybol.
• Consider color coding for applications in which users must distinguish rapidly among several categories of data, particularly when he data items are dispersed on the display.
• When blink coding is used, the blink rate should be 2 to 5 hertz with an ON cycle of 50 percent.
• For a large table that exceeds the capacity of one display frame, ensure that users can see column headings and row labels in all displayed sections of the table.
• When data display requirements change (which they will) provide some means for users (or the system manager) to make the necessary changes to display functions.

Grouping items together logically and in a structured format makes the display much easier to use.

Color

The principles developed by graphic artists are now being adapted for use with computer displays. Consider getting guidance form a graphic artist.

Some color guidelines

• Use color conservatively
• Limit the number of colors used.
• Recognize the power of color for coding.
• Place color coding under user control
• Design for monochrome first. this lets you concentrate on logic.
• Be consistent
• Be alert to common expectations about certain colors. Remember that some expectations are culture specific.
• Remember some people are color blind. The number is not insignificant.

Look at the ColorDemoApplet to examine how color contrasts in background a foreground work. The applet code.