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Detecting Connection and Disconnection Events

Several rules can detect changes in any connection, or in a direct connection only.

You can constrain the execution of the body of a rule that detects a connection/disconnection event by making such execution conditional on one of the functions described under Detecting Connectedness.

Generic Connection and Disconnection Events

A whenever rule can detect the establishment or breaking of a connection between two items irrespective of:

Whether the connection is direct or indirect.
The class(es) of the connection(s) that connect the items.
The direction(s) of the port(s) to which the connections attach.

The grammar is:

whenever item is connected to item

whenever item is disconnected from item

whenever any temp-control-monitor C 
is connected to any outer-thermometer T
	then start check-temp-progress (C, T)

Direct Connection and Disconnection Events

A whenever rule can detect the establishment or breaking of a direct connection between two items. The rule can fire for any direct connection, or only if the connection is:

Of a specified connection class
To a port that has a specified name
To a port that has a specified direction

The grammar is:

whenever a connection [of class class] 
    is directly {connected to | disconnected from} 
    [an input of | an output of | the portname of] item

When referring to a connecting that is directly connected to an item, G2 permits the use of a local variable. You cannot use a local variable when referring to a connection being directly disconnected from an item. Not using a local variable for a disconnected connection prevents the possibility of attempting to refer to a deleted item in the rule consequent.

whenever a connection of class pipe-connect is directly disconnected 
	from any tank T then start check-connection (T)

whenever any connection X is directly connected to 
	inflow-port of any tank T then start -inflow-rate (T, X)

whenever any connection of class my-connect is 
	directly connected to an input to any tank T 
	then conclude that the input-connection of T is true

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