What is the special feature of connections?

Every component of an embedded subprocess (Expanded status) must be connected to a subprocess object via the belongs to connection. This causes the component to be treated as a part of the subprocess. If this connection is missing, the component will be treated as part of the superior process. If a few objects are connected to the subprocess via the belongs to connection and others are not, the sequence flow will be interrupted.

See also

What is a subprocess (BPMN)?