In a service-request driven approach, the communication between blocks is based on asynchronous messages ("service requests") via SysML Standard Ports. A service request is always followed by an associated service at the receiving part – either state/mode change or operation.

The approach is performed in four steps:

1. It starts with the definition of the network nodes by means of SysML structure diagrams, using blocks as the basic structure elements. First, these blocks are empty and not linked.
2. In the next step, the communication between the blocks is described in a UML/SysML Sequence Diagram.
3. The next step is the allocation of the operational contracts to respective blocks.
4. Based on the allocated service requests, the associated SysML Standard Ports and Interfaces now can be defined.