Chapter 2

Guidelines, Principles, and Theories

Skip section on Theories

Outline

 

I.        Guidelines 

A.          Navigating the interface

        Sample of the National Cancer Institutes guidelines:

–        Standardize task sequences

–        Ensure that embedded links are descriptive

–        Use unique and descriptive headings

–        Use check boxes for binary choices

–        Develop pages that will print properly

–        Use thumbnail images to preview larger images

 

B.        Accessibility guidelines

•         Provide a text equivalent for every non-text element

•         For any time-based multimedia presentation synchronize equivalent alternatives

•         Information conveyed with color should also be conveyed without it

•         Title each frame to facilitate from identification and navigation

 

C.       Organizing the display

•         Smith and Mosier (1986) offer five high-level goals

–        Consistency of data display

–        Efficient information assimilation by the user

–        Minimal memory load on the user

–        Compatibility of data display with data entry

–        Flexibility for user control of data display

 

D.       Getting the user’s attention

•         Intensity

•         Marking

•         Size

•         Choice of fonts

•         Inverse video

•         Blinking

•         Color

•         Audio

 

E.        Facilitating data entry

•         Smith and Mosier (1986) offer five high-level objectives as part of their guidelines for data entry

–        Consistency of data-entry transactions

–        Minimal input actions by user

–        Minimal memory load on users

–        Compatibility of data entry with data display

–        Flexibility for user control of data entry

 

II.        Principles

      More fundamental, widely applicable, and enduring than guidelines

A.        Determine user’s skill levels
 

B.        Identify the tasks 
 

C.       Choose an interaction style

•         Direct Manipulation

•         Menu selection

•         Form fillin

•         Command language

•         Natural language

 

D.       The 8 golden rules of interface design

  1. Strive for consistency
  2. Cater to universal usability
  3. Offer informative feedback
  4. Design dialogs to yield closure
  5. Prevent errors
  6. Permit easy reversal of actions
  7. Support internal locus of control
  8. Reduce short term memory

 

E.        Prevent errors

•         Make error messages specific, positive in tone, and constructive

•         Correct actions

•         Complete sequences          

III.        Object/Action Interface model

A.          Syntactic-semantic model of human behavior

        used to describe

–        programming

–        database-manipulation facilities

–        direct manipulation

 

B.        Object-action design:

  1. understand the task.
  2. create metaphoric representations of interface objects and actions
  3. designer makes interface actions visible to users

 

C.       Task hierarchies of objects and actions

•         Decomposition of  complex systems

•         Interface Objects

ex. - directory: name, length, date of creation, owner, access control

ex. - files of information: lines, characters, fonts etc...

•         Interface Actions

–        load a text data file

–        insert into the data file

–        save the data file