Applications that solve complicated business problems and do a superior job in areas of security, performance and privacy may not achieve popularity. Why? In this entry we will introduce the field of usability engineering, with focus on user interface design heuristics that contribute to application quality.

Jakob Nielsen, one of the leading advocates in the field, has written a book on the subject, titled Usability Engineering. In the book he presented 10 UI design principles, that when implemented appropriately, would allow end users to achieve high level of satisfaction using applications. On any given systems, humans are the center of focus because we use applications to solve ours or others’ information needs. I encourage project managers, developers, designers and testers working in the application space consider applying these design principles or at the minimum, recognize the importance of usability.

Usability Heuristics [Nielsen 1994b]

1) Visibility of system status - The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

2) Match between system and the real world - The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order. 

3) User control and freedom - Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.

4) Consistency and standards - Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

5) Error prevention - Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.

6) Recognition rather than recall - Minimize the user's memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

7) Flexibility and efficiency of use - Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

8) Aesthetic and minimalist design - Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

9) Help users recognize, diagnose, and recover from errors - Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

10) Help and documentation - Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

[Useful Resources]

Usability Heuristics for Rich Internet Applications

Books by Neilsen-Norman Group

My favorite one is on Designing Web Usability: The Practice of Simplicity.
If you are working on IE based applications, it is a must read!