Module dependencies questions

[nkleban]

Why data module has domain module in dependencies list? Why in domain layer there is no dependency on data module? Why presentation layer has dependency on both domain and data layer?

"Data module"
dependencies { compile project(':domain') }

"Presentation module"
dependencies { compile project(':data') compile project(':domain') }

Shouldn't it be like a straight line?
"Presentation" depends on -> "Domain" depends on -> "Data"

[CROSP]

@nkleban I was confused with this at first. But you what you described is n-tier architecture, common approach used for ages. But in case of Clean Architecture more likely Onion Architecture is used.
This means that DomainLayer which is all business rules, core, kernel or whatever of your app, which should stay independent and operate only with interfaces.
In case of this example all data flow is implemented with RxJava
By the way, to make it more clear Presentation and Data layer can be on the same layer, because it is outer ring, above Domain.
This is how I understand this architecture. If I am wrong please let me know. @Trikke has great understanding of this architecture, so you can read my similar question #150

[nkleban]

@CROSP thank you for your explanation! I was confused by diagram where outer ring consists of only UI.