From the manual
Elements in a model are connected through any number of ports (AFPort), which are defined
by the element template (AFElementTemplate). A port can be defined as an input port, an
output port, or as an undirected port. The port defines how many connections can be made
and the types of elements that can be connected.
In analyses, directed ports (input and output ports) represent positive material flow and are
used by connections. Undirected ports are used by attachments of meters and analyzers. The
most common type of attachment in a model is a measurement or meter attached to a flow
A connection (AFConnection) represents the link between the ports of two elements. The
ports (AFPort), which are defined by the element template (AFElementTemplate), can be
defined as an input port, an output port, or as an undirected port.
Please note OSIsoft vCampus is intended to focus on topics related to PI programming and integration of PI with other systems; system administration/usage/configuration questions should continue to go to Tech Support.