Documents > Usability: what this is...
Usability, ISO definition 9241:11 (1998): "The extent to which a product can be used by specific users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use."

In other words, usability tends to simplify the use of a tool in order to make it more intuitive to defined users.
Human centered design processes for interactive systems, ISO 13407 (1999): “Human-centered design is an approach to interactive system development that focuses specifically on making systems intuitive and usable. It is a multi-disciplinary activity.
If this is a multi-disciplinary activity, then what type of domains does it integrate ?
Psychology & cognitive sciences, taxonomy and semantics
Business elements, processes, communication and marketing
This is exactly why it is so difficult to make information systems usable. Lying at the frontier of so many opposite interests, usability becomes a very challenging area... That is why you need a usability specialist with expertise and extended knowledge in these various domains. And in this, we can help.
And always remember: the best software developed with the best engineers, the best graphic designers on the best hardware will not work if not developed with and for the users !