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212816 (1) [Avatar] Offline
I think Figure 3.1 is missing the arrow from UI to Data as Fig 2.6 has.
Regards & thanks for bringing us a new edition.
Steven van Deursen (43) [Avatar] Offline
Thanks for your comment.

The extra arrow from UI to Data in figure 2.6 is added for illustrative purposes, but in fact such arrow is redundant, since project dependencies are transitive, which means that when project A depends on B, and B depends on C, it implies that A depends on C as well.

That's why in chapter 3 we choose again to use the simplified form where the arrow between UI and Data is not visible, but it is still there; the dependency is implied.

However, the theory about transitivity is explained in chapter 4 (see "The apparent dependency explosion"), not in chapter 3. Because of this, it might be good to make the dependency more explicit. We'll reconsider adding that arrow.

Thanks for your feedback.