An Across module bundles technical or business domain functionality, most often the latter. It represents a single Spring ApplicationContext that holds all the components the module defines and - optionally - makes these components available to other modules.
Across modules can depend on other modules. These dependencies will determine the relative order of a module versus other modules in the same application. A module will start (or ‘bootstrap’) after all the modules it depends on have already started. During the bootstrap phase a module can perform one or more initialization tasks through special installer components.
An Across application is usually made up of multiple Across modules. Most often a single Across module corresponds with a single jar file, but this is in no way an actual requirement. Every Across module has a unique name, and a single module descriptor that describes the basic configuration of the module.