Component Sets
There are a small number of component sets current in OFBiz (from lowest-level to highest-level):
1. framework
2. applications
3. specialpurpose
4. hot-deploy
Dependencies between components in these sets must ONLY go up the list. For example components in specialpurpose can depend on components in applications, but components in applications can not depend on components in specialpurpose.
Components Within Sets
framework
The framework is the underlying data structures and utilities that supply the essential common features used by the base applications and the extended components. These higher level components will have many dependencies on the framework components.
There should be no dependencies in the framework on other parts of OFBiz but a few have crept in. They are show as the gray arrows in the diagram. There should be a full discussion in the mailing list before any new dependencies are added.
base applications
The base applications components depend on each other as shown in the diagram. The reason these dependencies are needed is because the components are organized according to high level business concepts and in the real world business processes tend to jump between many of them. In technical terms this results in foreign keys from an entity in one component to an entity in another, and to service calls from services in one component to services in another, and other similar effects.
While components can depend on one another in the base applications set they should follow the established priority of dependencies. In the diagram below you see existing dependencies and the component dependency priority going from the top of the page down (in other words components higher on the page depend on components lower on the page).
Whenever some data structure or feature could go in multiple components, or could depend on elements in multiple components, the design should ensure that lower level components don't depend on something in the higher level ones.
The gray arrows in the diagram represent dependencies that violate the rule and are subject of on-going discussions about how to fix them.
specialpurpose
Components within the specialpurpose set should not depend on each other. If there is a need for components in this set to depend on something in another set, that something should be put into the most appropriate component in the applications set and both specialpurpose components can depend on the applications component.
hot-deploy
Hot deploy consists of user-define components that are not part of OFBiz. Components in this set are created as add-ons to OFBiz, so it is up to the author to manage it. The guidelines suggested for the specialpurpose component set are recommended here as well.
Other representations
In attachments of Framework-only distribution there is an Excel file with some dependencies not figured above. I did not check though that all the ones above are in the Excel file...