- Information Architecture
- Graphic (or Visual) Design
Your product manager's role is not to be an information architect, graphic designer, or usability expert. However, she should specify, in measurable terms, how usable the product should be. The usability requirements are the metrics by which we judge whether the designers have done a good job.
For more information on the distinction between designing for usability and specifying usability requirements, see this entry from November of last year.