The distribution model describes the ALE message flow between logical systems.
The relationships between logical systems, message types, BAPIs, and filters are defined in the distribution model. Applications and the ALE layer user the distribution model to determine receivers and to control the data distribution.
For more information about maintaining the distribution model see the Implementation Guide (IMG):
In the distribution model, you can specify the messages to be sent to a given logical system. You can also define the conditions for the content and dispatch of messages in the filters.
The distribution model consists of one or more views that you can define. With more complex distribution tasks you can assign business sub-areas or groups of logical systems to separate views.
The relevant views of the distribution model must be available in all the logical systems involved in ALE. You can find the functions for distributing views in Customizing for ALE.