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1. WO1996007258 - METHOD AND APPARATUS FOR NETWORK VARIABLE ALIASING

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[ EN ]

CLAMS
What is claimed is:

1. A method for resolving connection conflicts in a network, the method comprising the steps of:

a) detecting when a first network connection point of a node cannot be added to a second connection because said first network connection point belongs to a first connection, said first network connection
point corresponding to a network variable;

b) adding a second network connection point of the node to the second connection;

c) establishing a correspondence between said second network
connection point and said network variable;

d) if said network variable is an input network variable, then

i) updating said network variable responsive to messages
received on said first network connection point, and

ii) updating said network variable responsive to messages
received on said second network connection point; and e) if said network variable is an output network variable, then when said network variable is updated with a value,

i) transmitting the value in a first message identifying said first
connection though said first network connection point; and

ii) transmitting the value in a second message identifying said
second connection dirough said second network connection
point.

2. The method of Claim 1 wherein the step of establishing a correspondence between said second network connection point and said network variable includes the steps of:

providing an alias configuration table;

adding an entry to said alias configuration table, said entry corresponding to said second network connection point and containing

a selector identifying said second connection, and

a network vanable index identifying said network variable.

3. The method of Claim 1 wherein said network variable is defined in an
application associated with said node, wherein the step of establishing a correspondence between said second network connection point and said network variable includes the steps of:

defining an alias variable in said application;

establishing a correspondence between said alias variable and said network variable;

establishing a correspondence between said alias variable and said second network connection point;

wherein said step of updating said network variable responsive to messages received on said second network connection point includes

updating said alias variable responsive to messages received on said second network connection point includes, and

updating said network variable responsive to updating said alias
variable; and

wherein said step of transmitting me value in a second message identifying said second connection through said second network connection point includes

updating the alias variable with the value; and

transmitting the value in the second message responsive to updating the alias variable.

4. The method of Claim 3 wherein the step of establishing a correspondence between said alias variable and said network variable includes:

defining a netw╬▒rk-variable-to-alias map in said application; and

processing said network-variable-to-alias map to cause said network- variable-to-alias map to indicate a correspondence between said
network variable and said alias variable.

5. The method of Claim 1 wherein said network variable is an input network variable, the method further including the steps of:

when said second network connection point is polled, transmitting a response message dirough said second network connection point but not
through said first network connection point; and

when said first network connection pomt is polled, transmitting said response message through said first network connection point but not dirough said second network connection point.

6. An apparatus for communicating information between applications in a
network, the apparatus comprising: an input/output coupled to at least one node on the network by a first
connection;

a network connection point coupled to at least one node on the network by a second connection, wherein the second connection is different from said first connection;

memory containing

an application which defines a network variable;

a first indicator indicating that the network variable corresponds to the input/output;

a second indicator indicating that the input/output corresponds to the first connection;

a third indicator indicating that the network variable corresponds to the network connection point; and

a fourth indicator indicating that the network connection point
corresponds to the second connection;

connection and a second message over said second connection when said network variable is updated if said network variable is an output network variable; and an update mechanism for updating said network variable responsive to
messages over said first connection and responsive to messages over said second connection if said network variable is an input network a transmit mechanism for transmitting a first message over said first variable.

7. The apparatus of Claim 6 wherein said memory stores a network variable configuration table and an alias configuration table, wherein said second indicator is stored in an entry in the network variable configuration table, wherein said third indicator and said fourth indicator are stored in an entry in said alias configuration table.

8. The apparatus of Claim 7 wherein the transmit mechanism transmits the first message responsive to information contained in the entry in the network variable configuration table and transmits the second message responsive to information contained in the entry in the alias configuration table.

9. The apparanis of Claim 7 wherein the entry in the network variable
configuration table specifies a different message priority level than the entry in the alias configuration table.

10. A method for updating an input network variable associated with a node based on a first output network variable and a second output network variable, wherein the first ouput network variable and the second output network variable are both associated with a second node, comprising the steps of:

binding the input network variable to the first output network variable over a first connection through a primary network connection point;

binding the input network variable to the second output network variable over a second connection through an alias network connection point;

causing the first node to transmit a polling message over the first connection through the primary network connection point and over the second connection dirough the alias network connection point;

causing the second node to generate a first update message containing the value of the first output network variable over the first connection responsive to the polling message on the first connection; and

causing the second node to generate a second update message containing the value of the second output network variable over the second
connection responsive to the polling message on the second
connection; and

updating the input network variable responsive to the first update message and the second update message.