Usability is about systems that allow users to accomplish necessary tasks easily, efficiently , and with a minimum of errors. Usability means that users can achieve their goals with little, if any, frustration.
Usability is a core feature of your product brand. Like your brand, it touches every aspect of the product.
Winning solutions are usable; usability contributes to long- term profit.
A mental model is the set of thoughts and structures that we use to explain, simulate, predict, or control objects in the world.
A conceptual model is some representation of a mental model, in words or pictures, using informal or formal techniques.
Metaphors are models that help us understand one thing in terms of another.
Maintainability is enhanced by separating the user interface from the rest of the tarchitecture , even though there is no absolutely certain way to separate the influence of the user interface from the rest of the tarchitecture.
Performance matters. This isn't a justification for pursuing design decisions purely in the context of performance, but rather an acknowledgment that performance is always important.
Marketects want a way to confidently, reliably, and, above all, accurately answer performance questions. This is especially important in enterprise software.
There are a variety of techniques you can use to improve performance, including caching, working in the background, offloading work to other processors, or avoiding work entirely.