<xsd:documentation>Defines the external port in another Product Flow Model to which
an external port in this model is connected.
An external port should be connected to an external port with the opposite direction.
The connected external port must be in another Product Flow Model.
These connections should always be defined on a one-to-one basis. For example, if a facility
may receive input from multiple other facilities then a separate input port should be defined
for each of those facilities. This allows any question about mass balancing to be contained
within each individual model.
The external port name must match the name of an external port on the network
that represents this model.</xsd:documentation>