Real-time publish-subscribe system

• US 7,882,253 B2
• Filed: 04/05/2002
• Issued: 02/01/2011
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: Real-Time Innovations, Inc.
• Original Assignee: Real-Time Innovations, Inc.
• Inventors: Pardo-Castellote, Gerardo, Thiebaut, Stefaan Sonck, Hamilton, Mark
• Primary Examiner(s): SHAW, PELING ANDY
• Application Number:
  US10/118,470
• Publication Number:
  US 20020178273A1
• Time in Patent Office: 3,224 Days
• Field of Search: 709223-224, 709/230, 709/229, 715/736, 707/999.103, 707/999.104, 707/999.105, 707/999.106, 719/315, 719/316
• US Class Current: 709/230
• CPC Class Codes: G05B 2219/33149 Publisher subscriber, publisher, master broadcasts data to slaves, subscriber
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A real-time protocol for real-time network programming applications is disclosed. The protocol is executable on a computer network having a plurality of nodes that include applications, a network stack, an operating system, and middleware capable of executing real-time operations. The protocol can use group objects to model physical and logical devices connected to the network wherein each group object comprises at least one variable. Changes in these variables are encapsulated in variable change messages which are propagated in the network using communication objects. Also described is a real-time messaging format useful for implementing the protocol.

Claims

1. A method of operating a real-time protocol on a computer network having a plurality of nodes, wherein the nodes can include applications, a network stack, an operating system, and middleware capable of executing real-time operations, comprising:

operating the nodes of the computer network to use group objects to model physical and logical devices connected to the network wherein each group object comprises at least one variable;

operating the nodes of the network to use communication objects to communicate information about the variables in the form of variable change messages,

wherein

a variable is a data object that includes a plurality of parameters and a plurality of associated parameter values;

a variable includes parameters for a globally unique identifier and, implicitly or explicitly, for a type and a topic;

the communication objects include write communication objects and read communication objects;

the communication objects are associated with variables;

registering the read communication objects with the write communication objects whose associated variables have the same topic as the variable associated with the read communication objects; and

configuring each write communication object, in response to change information regarding the associated variable, to cause the change information regarding the variable to be provided to those read communication objects registered to receive information for that variable without the read communication objects otherwise requesting the change information.

2. The method of operating a real-time protocol of claim 1 wherein the at least one variable comprises at least one state variable.

3. The method of operating a real-time protocol of claim 1 wherein the at least one variable includes at least one sub-variable.

4. The method of operating a real-time protocol of claim 1 wherein the group object comprises a group object variable.

5. The method of operating a real-time protocol of claim 1 wherein one communication object includes a writer and another communication object includes a reader, wherein the writer is capable of writing variable change messages having a topic to associated readers that are registered to receive variable change messages having the topic.

6. The method of operating a real-time protocol of claim 5 wherein the writer uses timers to more efficiently write variable change messages to registered readers.

7. The method of operating a real-time protocol of claim 6 wherein the timers allow the writer to monitor variable message traffic written by other writers and based on analysis of the variable messages written by other writers use multicast to send variable messages to more than one registered reader.

8. The method of operating a real-time protocol of claim 6 wherein the timers can adaptively adjust message traffic in accordance with network capabilities.

9. The method of operating a real-time protocol of claim 6 wherein by making a time period of a timer longer the number of messages sent by the writer is reduced thereby reducing message traffic on the network.

10. The method of operating a real-time protocol of claim 6 wherein by making a time period of a timer shorter the number of messages sent by the writer is increased thereby reducing the number of variable change messages that the real-time middleware is required to store.

11. The method of operating a real-time protocol as in claim 5 wherein the writer can write variable change messages about different variables where the different variables have different formats.

12. The method of operating a real-time protocol of claim 11, wherein the changes to the different variables can be maintained in their logical order of occurrence even though the changes occur to different variables.

13. The method of operating a real-time protocol of claim 11, wherein the changes to the different variables can be grouped into an indivisible unit such that the readers can receive either all of the changes to the indivisible unit or none of the changes to the indivisible unit.

14. The method of operating a real-time protocol of claim 11, wherein the changes to the different variables are interpreted by the middleware as describing successive states of a group object whose state is defined as the aggregation of the values of all the variables it contains.

15. The method of operating a real-time protocol of claim 11, wherein the changes to the different variables can be combined together and substituted by GAPs such that the resulting states of the group object reconstructed by a reader are consistent with a subset of the actual states of the group object at a writer end.

16. The method of operating a real-time protocol of claim 11, wherein the changes to the different variables can be combined together and substituted by GAPs such that the resulting states of the group object reconstructed by a reader are consistent with a projected state of interest to the reader.

17. A method for writing a variable change message from a writer to a registered reader using a real-time protocol on a computer network having a plurality of nodes, wherein the nodes include at least one writer, at least one reader, and middleware capable of executing real-time operations,

wherein the writer and the reader of the computer network are associated with variables, a variable is a data object that includes a plurality of parameters and a plurality of associated parameter values, and a variable includes parameters for a globally unique identifier and, implicitly or explicitly, a type and a topic;

and

the reader of a node of the computer network is configured to register with a writer of another node of the computer network to receive information concerning topics for which write objects associated with the writer of the other node have variable information; and

the method comprising;

A. determining if there is a new reader;

B. where there is no new reader;

1) determining if there has been a change to a variable;

(a) if there are changes to the variable,

(i) the changes are saved as a variable change message;

(ii) a change sequence number is modified to reflect the addition of a new saved variable change message;

(iii) return to Step A, determining if there is a new reader;

(b) if there are no changes to the variable then return to Step A, determining if there is a new reader; and

C. where there is a new reader, a remote reader process is activated to update a registered reader of the computer network to cause the variable change message to be provided to registered readers, without the registered readers otherwise requesting variable change information.

18. The method of claim 17 wherein the activated remote reader process includes;

A. sending unsent variable change messages to the registered reader;

B. updating the positive acknowledgement status of the registered reader;

C. updating the negative acknowledgement status of the registered reader;

D. sending variable change messages that have been requested by the registered reader to the registered reader; and

E. sending heartbeat messages to the registered reader.

19. A method for a registered reader to read variable change message sent by a writer to the registered reader using a real-time protocol on a computer network having a plurality of nodes, wherein the nodes include at least one writer and a registered reader, and the writer and the reader are associated with variables;

a variable is a data object that includes a plurality of parameters and a plurality of associated parameter values;

a variable includes parameters for a globally unique identifier and, implicitly or explicitly, a type and a topic; and

the nodes also include middleware capable of executing real-time operations in the computer network, the method comprising;

A. determining if there is a writer for which the reader is registered to receive variable change messages;

B. where there is no writer, returning to Step A, determining if there is a writer; and

C. where there is a writer, a remote writer process is activated to update the registered reader in the computer network, without the registered reader otherwise requesting the updating.

20. The method of claim 19 wherein the activated remote writer process includes;

A. saving variable change messages received by the registered reader;

B. marking variable change messages identified in heartbeat messages as missing;

C. marking variable change messages identified in heartbeat messages as messages as requesting confirmation;

D. sending messages requesting the re-sending of the variable changes identified as missing; and

E. sending confirmation messages.