I assisted to my first presentation about User Experience Design (as I discovered, UX Design is not only UX). Here is a quick summary of what I still remember.
From what I understood UX Design is defined by:

•   aesthetic
•   functionality
•   innovation
•   enterprise impact
•   human factor (~ergonomics)

A product specification can then be described by a list of features, where each feature is defined by:

•   description (what is/does it?)
•   functional test (how to test the functionality?)
•   intend or goal (what's the objective of the feature, for e.g. "make user happy")
•   how to test/measure the feature (particularly its goal)

Relative reading (added in my reading queue):

• The Design of Everyday Things [Donald Norman, 1988]

D. Norman introduced the term affordance about user interaction, and emphasize on the design of product: "make the task dominate, make the tool invisible".