lectures 5,6 – workflows and internet process coordination
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Lectures 5,6 – Workflows and Internet Process Coordination. Middleware: the glue for network computing Workflows and Internet Workflows Enabling Technologies Static/Dynamic workflows Tasks and Events Transition Systems Workflow Patterns Liveness Deadlocks. Workflows. - PowerPoint PPT PresentationTRANSCRIPT
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Lectures 5,6 – Workflows and Internet Process Coordination
Middleware: the glue for network computingWorkflows and Internet WorkflowsEnabling TechnologiesStatic/Dynamic workflowsTasks and EventsTransition SystemsWorkflow PatternsLivenessDeadlocks
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Teleconferencing
Telemedicine
ElectronicMail
RemoteLogin
Financial
Layer 4 - Applications
Layer 3 - Middleware ServicesAuthentication
CoordinationStorage
Layer 2 - Transport Services
Layer 1 - Network Services
Text
Layer 0 - Technology Substrate
LANsWireless
DirectBroadcastSateliite
Video
ATM
Dial-upModems
VideoconferencingVideo & Audio
Services
WebServices
Audio
DistanceLearning
FinancialServices
Event Directory
ElectronicCommerce
FileTransfer
IP
Cable
FrameRelay
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Workflows
Informal definition.
Traditional applications:Office automation and document processingFactory automationBusiness
Internet workflows, iWM.Examples
Service gridsComputational grids
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Enabling technologies1980s 1990s 2000s
Sensors andWireless
Communication
Optical technologies forcommunication and data
storage
technology
time
Microprocessors
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Areas involved in iWM
HeterogeneousDatabaseSystems
KnowledgeEngineering
SoftwareEngineering
Modeling andAnalysis
Internet-BasedWorkflowManagement
DistributedSystems
SoftwareAgents
ComputerNetworks
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(b)
Process order
Assemble laptop
PC?
Assemble PC
Begin
Deliver product
End
Yes No
(a)
Prepare boxPrepare
motherboard
Install CPUInstall powersupply
Install memory
Start assembly of box andmotherboard
End assembly of box andmotherboard
Install screen
Install diskcontroller
(c)
Examine order
Gathercomponents
Assemble boxand motherboard
Installmotherboard
Install internaldisk
Install networkcard
Install videocard
Insert modem
Plug in CD andfloppy module
Plug in battery
Test assembly
Startassembly
End assembly
B
C
A
D
E
F
G
H
I
J
K
L
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Communication Plane
Resources for B
Communication for A
E
CD
G
F
Resources for G
Communication for G
Communication for BResource Plane
Resources for A
Resources for B
Resources for G
Process Plane
B
A
E
F
G
D C
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Lifecycle of a workflow
Creation – process definition
Process verification
Cases
Workflow enactment
The Workflow Management CoalitionMultibillion $ industryWorkflow Reference Model
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Other WorkflowEnactmentServices
WorkflowEnactmentServices
WorkflowClient
Applications
InvokedApplications
Process Definition Tools
Administrative &Monitoring Tools
Interface
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Interface
4
Interface 1
Interface 2 Interface 3
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Static/dynamic workflows
Static workflows
Dynamic workflowsException handlingReversibility.
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WorkflowDescription
User
PlanningEngine
VerificationEngine
EnactmentEngine
ComponentDatabase
WorkflowDescription
Case Activation Record
UnanticipatedException Handling
User
ProgrammingLanguage
ComputerProgram
WorkflowDescriptionLanguage
AutomaticProgramming
ComponentLibraries
Compiler
ObjectCode
Data
ProcessorRunning
the Process
WorkflowDatabase
(a) Workflows (b) Programs
Dynamic Workflows
Static Workflows Static Programs
Dynamic Programs
ProgramLibraries
Run-Time ProgramModification Requests
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Workflow enactment
Case: a particular instance of a workflow
Workflow enactment engine performs a coordination function
Tasks/Activities and Events.
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ProcessDefinition
ProcessInstantiation
Task (Activity)
Task (Activity)
Inactive Active
SuspendedCompleted
Enactment
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1
2 5
6
Install powersupply
7
4
Preparecase
Preparemotherboard
Install CPU
Install memory
Install diskcontroller
Installscreen
3
8
Done
9
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Transition systems
A directed graph: Nodes the states of the systemEdges eventsTwo distinguished states:
Initial state – no incoming edgeGoal/termination state – no outgoing edge
Example: laptop assembly. States labeled by the events causing the transition.
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S1
S2
S4
S3
S17
S6S5
S7
S10
S8
S13
S11 S12
S16
S14
S18
S9
S15
S19
S20
S21
(1)
(2) (5)
(2,5)(3)
(4)
(3,5) (2,6)
(3,6)
(4,5)
(4,6)
(4,7)
(4,8)
(9)
(3,8)
(2,8)
(2,7)
(3,7)
(6)
(7)
(8)
[2] [5][2,5]
[3,5] [2,6][2]
[6][3] [5]
[3,6]
[3] [6][4]
[5]
[4,5]
[5]
[4][6]
[4,6]
[6]
[4,7]
[4]
[7]
[7]
[8]
[9]
[4]
[4,8]
[4][8]
[8][2]
[2,8]
[7][2]
[2,7]
[3] [7]
[3,7]
[3]
[3]
[8][3,8]
1
2 5
6
Install powersupply
7
4
Preparecase
Preparemotherboard
Install CPU
Install memory
Install diskcontroller
Installscreen
3
8
Done
9
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Algorithm to construct the transition system from the event-task graph
1. Construct the set of E of individual events:
E={1,2,3,4,5,6,7,8,9}2. Split it into equivalence classes based upon the causality relationship:
E1 = {1,2,3,4,9} E2 = {1,5,6,7,8,9} The two sets are not disjoint!!
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Algorithm to construct the transition system from the event-task graph
3. Add to E all feasible combinations of events. Each feasible combinations contains one event from each class. Example:
[2,5], [3,5] are feasible combinations
[2,3] is not a feasible combination
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Algorithm to construct the transition system from the event-task graph
4. Construct the set of states S. Initially S contains only the initial state.Construct the set of all events feasible in that
state.For each event in that state label the state
reachable when the event occurs.Add the new state to SRepeat the process for every state in S.
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ChoicesA
B E
CD
G
F
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Liveness
A
B
CD
E
F
G
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Basic workflow patterns
Sequence
AND-split
Synchronization
XOR – spli
XOR – merge
OR – split
Multiple merge
Discriminator
N out of M join
Deferred choice
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A B C
a
A
B
C
AND
b
A
B
c
AND C
A
B
e
XOR CA
B
C
XOR
d
A
B
C
OR
f
A
B
C
AND
g
DXOR A
B
C
AND
h
DDIS
A
B
CAND
i
D
2/3 EA
B
C
XOR
j
X
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Resources and deadlocks
t1
t2
t3
t4
time
task A task B
r
q
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Agents and workflow enactment
Hybrid systems: some tasks carried out by computers, others by humans.
Why use agents for workflow enactment?
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WorkflowEnactment Engine
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
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EnactmentEngine AB
Top-LevelEnactment
Engine
Case Activation Record
Control Agent B
Task B
Control Agent A
Task A
Control Agent C
Task C
Control Agent D
Task D
Control Agent E
Task E
t0
t1
time
t2
t3
t4
t5
t6
t7
t8
EnactmentEngine CDE
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AuthoritativeWorkflow
Enactment Engine
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Control Agent
Task
Top-LevelWorkflow
Enactment Engine
AuthoritativeWorkflow
Enactment Engine