Discussion: Dependency relationships between Actors should be represented in SD and SR models using the standard Dependency Links notation. These links should reflect all types of dependency relationships between Actors. Contribution Links (solid lines) and Correlation Links (dotted lines) should not be used between Actors. In some i* models, especially those involving security or concepts discussed in advanced research, there is a need to show attacks and defense scenarios using correlations and contributions between Actors. They add new expressive power. These correlations and contributions between Actors are treated as extensions to i*.

Examples 1 and 2 depict some exceptional scenarios where Correlation and Contribution Links (solid or dotted lines) have been used between Actors to provide more expressiveness power. It is recommended that the beginners and students do not break the general rule or the guideline of not using Correlation and Contribution Links between actors.

Additionally, Correlation Links have been used in the NFR Framework’s examples. These links basically have the same syntax as Contribution Links, from any element only to Softgoals, but drawn in dotted lines. Correlation Links represent side effects from an element (such as a Task or a Softgoal) to a Softgoal. Example 3 depicts an NFR Framework using i* notation to illustrate the concept of codification of design knowledge for reuse and building NFR catalogues. The example shows the Operationalization of a Softgoal and its correlations (side effects) on other domain related Softgoals.