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:
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Contexts have roles;
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Roles fill other roles.
However, because we want to traverse these connections efficiently in both directions, we represent each by two links:
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In a context, we point to the roles, and
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a role contains a pointer to its context.
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In a role, we point to the role that fills it, and
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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.