12.4.1. A refresher: structural connections in Perspectives

Before we delve into these subjects, let’s quickly recap some aspects of the representation of Perspectives data. To start with, there are only two entities: contexts and roles. They are connected in just two ways:

  1. Contexts have roles;

  2. Roles fill other roles.

However, because we want to traverse these connections efficiently in both directions, we represent each by two links:

  1. In a context, we point to the roles, and

  2. a role contains a pointer to its context.

  3. In a role, we point to the role that fills it, and

  4. a role also contains pointers to roles that are filled by it.

And that’s it! In this text we will speak of the roles of a context, the context of a role, the filler of a role and the filled roles of a role.