In this chapter, we will present further applications of the notions of generic skill and competency developed in the previous chapters. The first of these applications is to define the concept of “competency gap” that extends the notion of “knowledge gap” introduced in Chapter 4 to guide the domain modeling process. Then, we show how we can use a model of the generic skill involved in a competency definition, to form the skeleton of an activity scenario. Afterwards, we use competencies to help define the roles and the resources needed by different actors in a virtual learning or knowledge management environment. Finally we use different viewpoints on a user’s competencies at the center of a user model that can help personalize or adapt a Web-based environment.