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To enable communications between a G2 process and a bridge, you create one or more GSI-INTERFACE objects, which specify the protocol to use, along with other relevant information about the remote process.

The GSI interface object acts as a doorway between G2 and the G2 Gateway bridge. Through the interface object, the KB receives data from and sends data to a bridge process.

Both the G2 process and the bridge are capable of sending and receiving data. G2 has the ability to pass knowledge as follows:

Type of exchange	Description
Value passing	Provides a value for a GSI variable from the bridge. GSI variables have GSI as their data server.
Item passing	Passes any item or object, with some set of its attributes, to the bridge process.

A G2 Gateway bridge process provides these additional capabilities:

• Once-per-second G2 polling, which permits G2 to obtain unsolicited data from the bridge process once every second.

• External scheduling (reporting by exception), indicating that value updates for variables occur automatically from the bridge process. G2 essentially turns off data seeking for the GSI variable, since it infers that updates will occur from the bridge. For a description of how G2 performs data seeking, see Obtaining Values for Variables.

From the G2 process, use remote procedure declarations to pass values, items, and objects to the GSI process. For a description of how to specify remote procedure declarations for data passing, see Using Remote Procedure Calls. The arguments are identical whether G2 is communicating to another G2 process or to a bridge.

G2 can also send text messages and acknowledgments to a bridge. Passing text and acknowledgments requires the use of GSI message objects.

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