Virtual machine and programming language for event processing

• US 8,627,299 B2
• Filed: 02/29/2008
• Issued: 01/07/2014
• Est. Priority Date: 02/29/2008
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Frank, Joachim H., Jamison, Wilfred C.
• Primary Examiner(s): Dam, Tuan Q.
• Assistant Examiner(s): Wei, Zheng
• Application Number:
  US12/040,485
• Publication Number:
  US 20090222793A1
• Time in Patent Office: 2,139 Days
• Field of Search: None
• US Class Current: 717/146
• CPC Class Codes: G06F 9/542 Event management; Broadcasting; Multicasting; Notifications

Abstract

A virtual machine supports execution of compiler-generated code and provides an execution environment for code that may correspond to any of several different event-driven or message-driven programming models (such as state machines, rules for complex event processing and event correlation, monitoring contexts, processes, and mediations). The programming models may be used in business monitoring and/or business integration environments. A programming language is defined for execution using the virtual machine, which contains a relatively small number of instructions and which is preferably generated by a compiler from a higher-level, event-driven or message-driven model.

Claims

1. A virtual machine for executing a program, comprising:

an instruction executor for executing instructions from the program using a computer, wherein;

the instructions from the program have been generated in an intermediate language, by a compiler, to cause processing of an execution sequence according to a specification of a model, the model specification encoded using a model notation that is distinct from the intermediate notation;

the instructions from the program are encoded in a markup language notation by the compiler and are selected by the compiler from allowable instructions of the intermediate language, the markup language notation being distinct from the intermediate language; and

the allowable instructions of the intermediate language comprise;

an event instruction for receiving an inbound event;

an assignment instruction for assigning a value;

a branch instruction for conditional transfer to a different one of the instructions;

an emit instruction for specifying that an outbound event is to be emitted;

a terminate instruction for specifying that a current execution context object is to be terminated; and

a fan-out instruction for at least one of specifying event correlation and enabling a context switch, the context switch causing a particular execution context object to be used as the current execution context object.

2. The virtual machine according to claim 1, wherein the model specification is an event-driven model specification.

3. The virtual machine according to claim 1, wherein the model specification is a message-driven model specification.

4. The virtual machine according to claim 1, wherein the virtual machine is usable for executing a plurality of programs, the plurality of programs generated, by at least two different compilers, to cause processing of respective execution sequences according to at least two different specifications of execution models.

5. The virtual machine according to claim 1, wherein the executing of the event instruction further comprises:

executing the event instruction to receive a particular inbound event according to the specification of the model;

locating a fan-out instruction associated with the event instruction;

executing the located fan-out instruction to determine, using correlation predicate information associated with the located fan-out instruction, zero or more execution context objects to use for processing the particular inbound event; and

directing the particular inbound event to each determined execution context object, if any, for the processing of the particular inbound event therein.

6. The virtual machine according to claim 1, wherein the event instruction for receiving an inbound event specifies a filter that is to be evaluated by the virtual machine instruction executor, responsive to receiving a particular inbound event, to determine whether the event instruction is applicable for processing the particular inbound event.

7. The virtual machine according to claim 1, wherein the virtual machine instruction executor determines which of a plurality of event instructions from the program to execute, upon receiving a particular inbound event, by comparing a type declared by the particular inbound event to a type specification, when present, in each of the plurality of event instructions.

8. The virtual machine according to claim 1, wherein the executing of the assignment instruction further comprises:

evaluating an expression of the assignment instruction; and

assigning, as the value, a result of the evaluating to a target identified by the assignment instruction, the target comprising a slot of a current execution context object or of an outbound event that is to be emitted.

9. The virtual machine according to claim 1, wherein the executing of the branch instruction further comprises:

evaluating a condition expression of the branch instruction; and

wherein the conditional transfer further comprises next executing the different one of the instructions, as identified by an attribute of the branch instruction, when the evaluation returns a true result, and otherwise next executing a next sequential one of the instructions.

10. The virtual machine according to claim 1, wherein the executing of the emit instruction further comprises emitting, to an event bus, the outbound event.

11. The virtual machine according to claim 10, wherein the executing of the emit instruction further comprises evaluating an expression specified on the emit instruction and reflecting a result of the evaluating in the outbound event prior to the emitting.

12. The virtual machine according to claim 1, wherein the executing of the terminate instruction further comprises terminating the current execution context object.

13. The virtual machine according to claim 1, wherein the virtual machine instruction executor executes the instructions of the program by:

detecting arrival of an inbound event;

comparing the inbound event to each event instruction from the program to determine if the event instruction from the program is applicable for processing the inbound event; and

for each event instruction from the program which is determined to be applicable for processing the inbound event, performing;

obtaining subordinate instructions of the event instruction, the subordinate instructions comprising zero or more of;

the assignment instruction, the branch instruction, the emit instruction, the fan-out instruction, and the terminate instruction; and

executing each of the zero or more obtained subordinate instructions.

14. The virtual machine according to claim 13, wherein:

executing the fan-out instruction of an applicable event instruction, responsive to detecting the arrival of the inbound event, causes selection of one or more particular existing context object as the current execution context object, or creation of a new execution context object and selection of the new execution context object as the current execution context object; and

the selected current execution context object is used when executing each next-sequential one of the obtained subordinate instructions until encountering one of;

the terminate instruction, and then terminating the current execution object when executing the terminate instruction;

or another fan-out instruction, and then selecting a different execution context object as the current execution context object when executing the other fan-out instruction.

15. A computer program product for executing a virtual machine, wherein the computer program product is embodied on one or more non-transitory computer-readable storage media and comprises computer-readable instructions for:

obtaining instructions from a program, the instructions from the program having been generated in an intermediate language, by a compiler, to cause processing of an execution sequence according to a specification of a model, the model specification encoded using a model notation that is distinct from the intermediate notation, and

executing the obtained instructions from the program using the virtual machine on a computer, wherein the instructions from the program are encoded in a markup language notation by the compiler and are selected by the compiler from allowable instructions of the intermediate language, the markup language notation being distinct from the intermediate language, the allowable instructions of the intermediate language comprising;

an event instruction for receiving an inbound event;

an assignment instruction for assigning a value;

a branch instruction for conditional transfer to a different one of the instructions;

an emit instruction for specifying that an outbound event is to be emitted;

a terminate instruction for specifying that a current execution context object is to be terminated; and

a fan-out instruction for at least one of specifying event correlation and enabling a context switch, the context switch causing a particular execution context object to be used as the current execution context object.

16. A non-transitory computer-readable storage medium storing source code written in a programming language, wherein:

the programming language comprises an intermediate language which is generated, by a compiler, to cause processing of an execution sequence according to a specification of a model, the model specification encoded using a model notation that is distinct from the intermediate notation, and allowable instructions of the intermediate language comprising;

an event instruction for receiving an inbound event;

an assignment instruction for assigning a value;

a branch instruction for conditional transfer to a different one of the instructions;

an emit instruction for specifying that an outbound event is to be emitted;

a terminate instruction for specifying that a current execution context object is to be terminated; and

a fan-out instruction for at least one of specifying event correlation and enabling a context switch, the context switch causing a particular execution context object to be used as the current execution context object; and

the source code comprises a plurality of the allowable instructions of the programming language which are selected by the compiler, wherein the source code is encoded by the compiler, during the generating, in a markup language notation and is executable to cause processing of the execution sequence according to the specification of the model.

17. The computer-readable medium according to claim 16, wherein model specification is an event-driven model specification.

18. The computer-readable medium according to claim 16, wherein the model specification is a message-driven model specification.

19. A program of instructions stored on a non-transitory computer-readable storage medium which, when executed, causes a computer to perform:

obtaining the instructions from the program, the instructions from the program having been generated in an intermediate language, by a compiler, to cause processing of an execution sequence according to a specification of a model, the model specification encoded using a model notation that is distinct from the intermediate notation; and

executing the obtained instructions from the program, wherein the instructions from the program are encoded in a markup language notation by the compiler and are selected by the compiler from allowable instructions of the intermediate language, the markup language notation being distinct from the intermediate language, the allowable instructions of the intermediate language comprising;

an event instruction for receiving an inbound event;

an assignment instruction for assigning a value;

a branch instruction for conditional transfer to a different one of the instructions;

an emit instruction for specifying that an outbound event is to be emitted;

a terminate instruction for specifying that a current execution context object is to be terminated; and

a fan-out instruction for at least one of specifying event correlation and enabling a context switch, the context switch causing a particular execution context object to be used as the current execution context object.

20. The program of instructions according to claim 19, wherein the model specification is an event-driven model specification.

21. The program of instructions according to claim 19, wherein the model specification is a message-driven model specification.