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Application of Coloured Petri Net for Agent Control and
Communication in the ABAsim Architecture
Antonín KavičkaUniversity of Pardubice, Czech Republic
Michal ŽarnayUniversity of Žilina, Slovak Republic
CPN'08 Workshop 2
Outline
• Background and motivation
• Definition of ABA-CPN (Agent-based architecture – Coloured Petri net)
• Application example
• Conventions in ABA-CPN
• Analysis of ABA-CPN
• Conclusion
CPN'08 Workshop 3
Background
Simulation of large and complex logistic nodes using ABAsim architecture (agent-based architecture of simulation models)
CPN'08 Workshop 4
ABAsim – Agent’s Decomposition
Query Monitor
MANAGER
Actuation
Perception
Solving support
Agent
Human operator
Communication
SchedulerAdvisor
Action
Process
Agent
Effectors
Solvers
Sensors
CPN'08 Workshop 5
ABAsim – Hierarchy of Agents
MANAGER
agent
Service controller
agent Surroundings
Incoming flow
StartFinished
Notice : Customer
arrives
MANAGER
Service A
MANAGER
Resource transfer
StartFinished
agentResource controller
Notice : Customer leaves
Notice : Customer has just arrived
Service B
Customer transfer
Start
Finished
Request : Deliver resource
Response : Resource delivered
Notice : Resource returnedFinishedStart Start
Finished
CPN'08 Workshop 6
ABA-graph
Service controller
Resourceselection
Enqueuingresource request
Resourceassignment
Transfer needed ?
Resource transfer
Resourcerelease
Queuing forresource ?
Resource transfer
t1
t2
t3
t4
t5
t6
t7
t8
p1
p2
p6
p3
p4
p5
p7
p8
p9
p10
p11
p12
p13
p14
p15
p16
p17
Yes
No
Yes
No
Code
Service controller
Service controller
Code
Result
Result
Result
Available
Otherwise
Dequeuingresource request
Assignresource
Finished
Resourcereturned
Start
Resourceassigned
Otherwise
Absorption
p18
X(t7)=1
• Definition of agent’s control and communication• Subclass of Place/Transition Petri net
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Motivation
• Upgrade to a subclass of coloured Petri nets in order to:– use a more flexible approach in describing
the agent’s components– use existing tools for an analysis
CPN'08 Workshop 8
Outline
• Background and motivation
• Definition of ABA-CPN
• Application example
• Conventions in ABA-CPN
• Analysis of ABA-CPN
• Conclusion
CPN'08 Workshop 9
What is ABA-CPN
• Describes reactive logic of an agent component (edited within the CPN Tools environment)
• Token colours correspond to messages• Denoted transitions correspond to agent’s instant
assistants• Management of token instances is based on prefix
conventions of identifiers used in arc expressions• Evolution is realized by means of a system interpreter
within the ABAsim run-time kernel
CPN'08 Workshop 10
Definition of ABA-CPN
• Based on definition of CPN
• Net structure:P = {pin} {pout} PS
T = TD TA TS TB
• Additional rules
OM_D
OM_Finpinp
res
if res=Res_Ethen 1`reselse empty
res
if res=Res_CplusDthen 1`reselse empty
res
if inp=IM_Bthen 1`inpelse empty
inp res
inp
xx
inp
OM_C
OM_E
s3
d2
d1 a1
a2
t1
s2
s1
p7
InMSG
p6
Result
p5
Result
p4
Result
p8
Generic
p3
InMSG
p9
p2
InMSG
p1
IM_A
InMSG
if inp=IM_Athen 1`inpelse empty
OutMSG
Input place pin
Output place pout
Internal places PS
OM_D
OM_Finpinp
res
if res=Res_Ethen 1`reselse empty
res
if res=Res_CplusDthen 1`reselse empty
res
if inp=IM_Bthen 1`inpelse empty
inp res
inp
xx
inp
OM_C
OM_E
s3
d2
d1 a1
a2
t1
s2
s1
p7
InMSG
p6
Result
p5
Result
p4
Result
p8
Generic
p3
InMSG
p9
p2
InMSG
p1
IM_A
InMSG
if inp=IM_Athen 1`inpelse empty
OutMSG
Decision transitions TD
Assistant transitions TD
representing actions in simulation
Standard transitions TD
Sending transitions TD
OM_Finpinp
res
if res=Res_Ethen 1`reselse empty
res
if res=Res_CplusDthen 1`reselse empty
res
if inp=IM_Athen 1`inpelse empty
if inp=IM_Bthen 1`inpelse empty
inp res
inp
xx
inp
OM_C
OM_E
s3
d2
d1 a1
a2
t1
s2
s1
p7
InMSG
p6
Result
p5
Result
p4
Result
p8
Generic
p3
InMSG
p9
OutMSG
p2
InMSG
p1
IM_A
InMSG
OM_D
Decision arcs
Elementary variable arcs(all the remaining)
Constant arcs
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Tokens
Reflect message forms used for communication that may be filled differently throughout the net evolution
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Initial Markings
(|M0(p)| = 1, p = pin) (|M0(p)| = 0, p ≠ pin)
M0 = { jM0 | j =1,2, …, |C(pin)|},for i ≠ j, iM0(p) ≠ jM0(p)
Admissible initial marking: input message before processing and no other messages being processed
Set of admissible initial markings: all relevant input messages
OM_D
OM_Finpinp
res
if res=Res_Ethen 1`reselse empty
res
if res=Res_CplusDthen 1`reselse empty
res
if inp=IM_Bthen 1`inpelse empty
inp res
inp
xx
inp
OM_C
OM_E
s3
d2
d1 a1
a2
t1
s2
s1
p7
InMSG
p6
Result
p5
Result
p4
Result
p8
Generic
p3
InMSG
p9
p2
InMSG
p1
IM_A
InMSG
if inp=IM_Athen 1`inpelse empty
OutMSG1 1`IM_A
Another option: 1`IM_B
CPN'08 Workshop 17
Outline
• Background and motivation
• Definition of ABA-CPN
• Application example
• Conventions in ABA-CPN
• Analysis of ABA-CPN
• Conclusion
Example Introduction
MANAGER
agent
Service controller
agent Surroundings
Incoming flow
StartFinished
Notice : Customer
arrives
MANAGER
Service A
MANAGER
Resource transfer
StartFinished
agentResource controller
Notice : Customer leaves
Notice : Customer has just arrived
Service B
Customer transfer
Start
Finished
Request : Deliver resource
Response : Resource delivered
Notice : Resource returnedFinishedStart Start
Finished
Example of ABA-CPN
Dequeueapplicant
Queuefor releasedresource?
Enqueueapplicant
Selectionfrom availableresources
Resourcerelease
y
x6bx6a
y
x_No_transferx_No_transfer
if x5=FIN_Transferthen 1`x_No_transferelse empty
x6a
x6b
x6b
x0
if x5=REQ_Deliver_resourcethen 1`x5else empty
x5x5
if x5=NTC_Resource_returnedthen 1`x5else empty
x5
x6bx6ax6a
if x6a=Resource_availthen 1`x6aelse empty
if x6a=No_resourcethen 1`x6aelse empty
x6a
x6c
if x6c=Non_empty_queuethen 1`x6celse empty
x6cx6cx5
x6ax5
a7
t1
s2
s1
a2
d4a5
a4
d2
a6
d3a3
a1
d1
p13
Generic
p11
Result_b
p14
Result_b
p15
Result_b
p16
p12
Result_b
p10
Result_a
p7
Result_a
p6
Result_a
p9Result_c
p8
Result_c
p5
InMSG
p4
Result_a
p1
InMSG
p3
InMSG
p2
InMSG
Resourceassignment
Transfer toapplicant?
if x6b=No_transferthen 1`x6belse empty
if x6b=Transferthen 1`x6belse empty
OutMSG
x_START_Transfer
x_RESP_Resource_delivered
a8
Updatetransferstatistics
CPN'08 Workshop 20
Outline
• Background and motivation
• Definition of ABA-CPN
• Application example
• Conventions in ABA-CPN
• Analysis of ABA-CPN
• Conclusion
CPN'08 Workshop 21
Conventions in ABA-CPN
• Management of token instances– First character (prefix)– Second character for decision transitions
• Denoting of places
• Third character
• Constant identifiers
CPN'08 Workshop 22
Prefix Convention
y
t1
p13
Generic
p11
Result_b
p15
Result_b
x_No_transferx_No_transfer
CPN'08 Workshop 23
“Decision Transitions” Convention
Resourceassignment
Enqueueapplicant
x6a
x6a
if x6a=Resource_availthen 1`x6aelse empty
if x6a=No_resourcethen 1`x6aelse empty
x6a
a5
a4
d2
p7
Result_a
p6
Result_a
p4
Result_a
Resourceassignment
Enqueueapplicant
x6a
x6a
if x6a=Resource_availthen 1`x6aelse empty
if x6a=No_resourcethen 1`x6aelse empty
x6a
a5
a4
d2
p7
Result_a
p6
Result_a
p4
Result_a
CPN'08 Workshop 24
Outline
• Background and motivation
• Definition of ABA-CPN
• Application example
• Conventions in ABA-CPN
• Analysis of ABA-CPN
• Conclusion
CPN'08 Workshop 25
Analysis of ABA-CPN
• To check correctness of the ABA-CPN, the liveness properties are used:– Dead markings– Transitions liveness
CPN'08 Workshop 26
Dead Markings – 2 Types
(|M(pout)| ≥ 1) (|M(p)| = 0, p ≠ pout)
|M(p)| = 0, p P
sending a message from the current agent to another agent
consumption of the message form and no need for further communication
CPN'08 Workshop 27
Conditions from Transitions Liveness
The only transition occurring in all sequences: input transition t TD
No transition is dead in all occurrence sequences for all admissible initial markings
CPN'08 Workshop 28
Conclusion
• Benefits of the ABA-CPN compared to the ABA-graph:– higher modelling capabilities of CPN:
• construction of conditional branching and • differentiation of various instances of messages
– existing tools for the CPN analysis
CPN'08 Workshop 29
Use of the ABA-CPNCreate an ABA-CPN model
Analyze its liveness properties
Import the model
Check the model syntax
Interpret the model during simulation runs
CPN Tools
ABA-CPN Interpreter
