The following is a summary of the organization of the ONOS source tree. This section is not intended to be comprehensive list of all packages and files, but rather an overview to provide developers with a general idea of how ONOS is organized (think man hier on UNIX).

POM Hierarchy

ONOS is organized as multiple projects, each with its own pom.xml file so that it can be built with Maven. The pom.xml files are organized in a hierarchy, so that projects with shared dependencies and configurations can be built from a parent pom.xml file defined closer to the root.The root of the source tree contains the top-level pom file that builds all of the projects comprising ONOS.

Since the POM hierarchy reflects the logical organization of ONOS, it is used as the reference for this page. 

Project Layout

The project root directory
Domain-agnostic and third-party utilities
Unit testing
ONOS data types, graph representations, etc.
Asynchronous messaging 
I/O loop handling
Wrappers for leveraging OSGi
Basis for JAX-RS web resources
API, network model, clustering, etc. 
North- and south-bound API definitions
Distributed Stores
Single-instance Stores
REST API resources
ONOS GUI reosurces
Karaf CLI extensions for ONOS commands
Protocol-specific providers
Applications - demos, samples, and use cases
OpenFlow libraries & IO loop 
OpenFlow provider/switch - related APIs
Controller and switch object implementations
Developer/test utilities and configuration files
Developer utilities - IDE settings, bash aliases, etc.
Build tools and configurations for Jenkins, Sonar, etc.
Configurations used for packaging
ONOS scripts, cell definitions, Mininet topologies, etc. 
target directory for Javadocs