Communication in a distributed system

• US 20060230201A1
• Filed: 04/08/2005
• Published: 10/12/2006
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Crawford, Lara S., Hindi, Haitham A., Fromherz, Markus P. J.
• Granted Patent: US 8,819,103 B2
• Time in Patent Office: Days
• US Class Current: 710/62
• CPC Class Codes: H04L 41/00 Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
• CPC Class Codes: H04L 41/044 comprising hierarchical management structures
• CPC Class Codes: H04L 41/08 Configuration management of networks or network elements address allocation H04L61/50
• CPC Class Codes: H04L 41/0826 for reduction of network costs H04L41/0833 takes precedence
• CPC Class Codes: H04L 41/0883 Semiautomatic configuration, e.g. proposals from system
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies

Abstract

Controllers communicate commands in terms of goals and constraints. A goal is an objective. A constraint is information regarding how the goal is to be achieved. For example, a constraint may specify when, or how much of, a resource may be used to achieve a goal. Additionally, or alternatively, a constraint may specify an acceptable or expected accuracy or tolerance regarding how the goal is achieved. Each controller is expected to achieve assigned goals in accord with associated constraints. Thereby, system communication may be reduced. If controllers achieve goals according to specified constraints, the controllers do not need to provide updates or be updated regarding the status of activities of other controllers or regarding other operational context information. In some embodiments, commands are generally not acknowledged. Instead, serving controllers respond to a command with an error message if a goal cannot be met in accord with an associated constraint.

Claims

1. A method for communicating between a first element and a second:

element in a system, the method comprising;

determining at least one goal related to a task to be performed by the second element;

determining at least one constraint related to how the at least one goal is to be achieved;

communicating the at least one goal and the at least one constraint to the second element; and

receiving an error message if the second element is not capable of achieving the at least one goal in accord with the at least one constraint.

2. The method of claim 1 further comprising:

evaluating the at least one goal and the at least one constraint in light of capabilities of the second element; and

communicating an error message if the evaluation indicates that the second element is not capable of achieving the at least one goal in accord with the at least one constraint.

3. The method of claim 1 further comprising:

determining an information source able to provide source information that would be useful in achieving the at least one goal; and

subscribing to the source information.

4. The method of claim 3 further comprising:

receiving the subscribed to source information; and

communicating the received source information to the second element.

5. The method of claim 1 further comprising:

determining status information available from the second element that would be useful in monitoring progress of the second element in achieving the at least one goal;

subscribing to the determined status information.

6. The method of claim 5 further comprising:

communicating the subscribed to status information to the first element.

7. The method of claim 1 wherein communicating the at least one goal and the at least one constraint comprises:

assembling a message including a command type, a command identifier, a command specification and a command time; and

transmitting the assembled message from the first element to the second element.

8. The method of claim 3 wherein subscribing to the source information comprises:

assembling a message including an action type, a command identifier, a subscription specification and a subscription time; and

transmitting the assembled message.

9. The method of claim 5 wherein subscribing to the status information comprises:

assembling a message including an action type, a command identifier, a subscription specification and a subscription time; and

transmitting the assembled message.

10. The method of claim 4 wherein communicating the received source information comprises:

assembling a message including an action type, a command identifier, a publication specification and a publication time; and

transmitting the assembled message.

11. The method of claim 6 wherein communicating the status information comprises:

assembling a message including an action type, a command identifier, a publication specification and a publication time; and

transmitting the assembled message.

12. The method of claim 1 further comprising:

determining at least one new goal related to the task to be performed by the second element;

determining at least one new constraint related to how the at least one new goal is to be achieved;

communicating the at least one new goal and the at least one new constraint to the second element; and

receiving an error message if the second element is not capable of achieving the at least one new goal in accord with the at least one new constraint.

13. The method of claim 12 wherein communicating the at least one new goal and the at least one new constraint to the second element comprises:

assembling a replace message including a command type of—

replace—

, the command identifier and a replacement command specification selecting a replacement capability of the second element and at least one replacement goal, and indicating at least one replacement constraint on an aspect of how the at least one replacement goal is to be achieved.

14. The method of claim 12 wherein communicating the at least one new goal and the at least one new constraint to the second element comprises:

assembling a cancel message including a command type of—

cancel—

, and the command identifier.

15. The method of claim 14 further comprising:

assembling a new command message including a command type of—

set—

, a new command identifier and a new command specification selecting a new capability of the second element and at least one new goal, and indicating the at least one new constraint on at least one aspect of how the new at least one goal is to be achieved.

16. The method of claim 1 wherein determining at least one goal comprises:

determining a trajectory including a plurality of starting points and ending points in association with respective starting times associated with the starting points.

17. The method of claim 1 wherein determining at least one constraint related to how the at least one goal is to be achieved comprises:

at least one of determining at least one set of upper and lower bounds for the at least one goal and determining at least one resource allocation for achieving the at least one goal.

18. The method of claim 2 wherein evaluating the at least one goal and the at least one constraint in light of capabilities of the second element comprises:

accessing second element capabilities data based on the at least one goal; and

comparing the at least one constraint to the accessed second element capabilities data, thereby determining if achieving the at least one goal in accord with the at least one constraint is within the capabilities of the second element.

19. The method of claim 2 wherein evaluating the at least one goal and the at least one constraint in light of capabilities of the second element comprises:

attempting to achieve the at least one goal in accord with the at least one constraint;

monitoring progress of the attempt; and

determining that achieving the at least one goal in accord with the at least one constraint is outside the capabilities of the second element, if the monitored progress indicates that the attempt is unsuccessful.

20. A document processing system comprising:

a first xerographic marking engine;

a transport system that is operative to transport media to and/or from the first marking engine, the transport system including a plurality of transport actuators;

at least one actuator controller that is operative to control at least one transport actuator of the plurality of transport actuators to transport print media based on at least one received goal and at least one received constraint; and

at least one supervisory controller that is operative to communicate at least one goal and at least one constraint to the at least one actuator controller.

21. The system of claim 20 further comprising:

a plurality of transport sensors, wherein each of the plurality of transport sensors is operative to sense and report one or more aspect of the transportation of the print media as it is transported by the transport system, wherein at least one of the at least one actuator controller and the at least one supervisory controller is operative to select a subset of the plurality of sensors based on the received at least one goal, and to subscribe to information reported by the selected subset of sensors.

22. The system of claim 20 further comprising:

at least a second marking engine, wherein the transport system is further operative to transport media to and/or from the at least a second marking engine; and

at least one marking engine controller that is operative to control at least one aspect of processing of at least the second marking engine based on at least one received goal, wherein the at least one supervisory controller is operative to communicate the at least one goal to the at least one marking engine controller.

23. A method that is operative to coordinate activities of a plurality of controllers in a document processing system, the method comprising:

determining a processing path through the document processing system for a sheet of print media, the path including a first module that is tightly coupled to a second module, whereby for at least a portion of a processing performed by the system both the first module and the second module operate on the sheet at the same time;

determining respective first and second controllers associated with the first and second modules;

determining respective cooperative first and second goals and constraints for actions of the first module and the second module;

communicating the respective first cooperative goal and constraint to the first controller; and

communicating the respective second cooperative goal and constraint to the second controller.

24. The method of claim 23 wherein determining cooperative goals and constraints comprises:

determining at least one of compatible speeds of operation and directions to direct the sheet, for the first and second modules, whereby the sheet of print media will not be damaged as the sheet is simultaneously acted upon by the first and second modules.

25. A system comprising:

a first system element;

a second system element; and

a communication link between the first element and the second element, wherein the first system element is operative to determine at least one goal related to a task to be performed by the second element, to determine at least one constraint related to how the at least one goal is to be achieved by the second element and to communicate the at least one goal and the at least one constraint to the second element in a message carried over the communications link, and wherein the second system element is operative to receive the message carried over the communications link, evaluate the at least one goal and the at least one constraint in light of capabilities of the second element and to communicate an error state in a message carried over the communications link to the first element, if the evaluation indicates that the second element is not capable of achieving the at least one goal in accord with the at least one constraint.

26. The system of claim 25 further comprising:

a plurality of sensors, wherein each of the plurality of sensors is operative to sense and report one or more aspects of the task performed by the second element, wherein the second element is operative to select a subset of the plurality of sensors based on the received at least one goal and to subscribe to information reported by the selected subset of sensors.

27. The system of claim 25 further comprising:

a plurality of sensors, wherein each of the plurality of sensors is operative to sense and report one or more aspects of the task as the task is performed by the system, and wherein the first element is operative to select a subset of the plurality of sensors based on the, at least one communicated goal and to subscribe to information reported by the selected subset of sensors.

28. The system of claim 27 wherein the first element is further operative to communicate to the second element, aspects of task information received, directly or indirectly, from the subset of sensors, based on the subscription.

29. The system of claim 28 wherein the second element is further operative to receive the aspects of task information from the first element and evaluate at least one aspect of performance based on the received aspects of task information.

30. The system of claim 25 wherein first element is operative to communicate the at least one goal and the at least one constraint by assembling a message including a command type, a command identifier, a command specification and a command time, and communicating the assembled message to the second element.

31. The system of claim 26 wherein the second element is operative to subscribe to the information reported by the selected subset of sensors by assembling a message including an action type, a command identifier, a subscription specification and a subscription time and transmitting the assembled message.

32. The system of claim 27 wherein the first element is operative to subscribe to the information reported by the selected subset of sensors by assembling a message including an action type, a command identifier, a subscription specification and a subscription time and transmitting the assembled message.

33. The system of claim 25 wherein the first element is further operative to subscribe to the status information of the second element by assembling a message including an action type, a command identifier, a subscription specification and a subscription time and transmitting the assembled message.

34. The system of claim 33 wherein the first element is operative to assemble the message by including an action type of—

subscribe—

; and

including a list of one or more variables to which the supervisory controller is subscribing and wherein the second element is operative to communicate the subscribed to status information to the first element by assembling a message including an action type, a command identifier, a publication specification and a publication time, and transmitting the assembled message.

35. The system of claim 34 wherein the second element is operative to assemble the message by including an action type of—

update—

and including a publication specification specifying at least one variable value of at least one variable to which the supervisory controller subscribed.

36. The system of claim 25 wherein the second element is further operative to evaluate the at least one goal and the at least one constraint in light of capabilities of the second element and to communicate an error message to the supervisory controller if the evaluation indicates that the actuator-controller is not capable of achieving the at least one goal in accord with the at least one constraint.