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Department of Computer Science and Engineering
Southern Methodist University
03/17/08 1
LiGuo [email protected]
Department of Computer Science & Engineering
Southern Methodist University
Modeling Value-Based Process with Object Petri-Nets
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 2
Value-Based Software Quality Achievement (VBSQA) Process
Build-to Plans(Life Cycle Architecture)
LCA
Q-tradeoff analysis; negotiate
agreements;
V&V
Q-attributes conflict, risks; risk mitigation
spirals; solution options
Execute Plans(Construction)
…
…
IOC
Top Level Plans(Life Cycle Objectives)
Q-tradeoff analysis; negotiate
agreements; V&V plans
Q-attributes conflict, risks; risk mitigation
spirals; solution options
Mission objectives, scenarios (including software Q-attributes goals);
cost/benefit analysis
LCO
System Acquirer
DB Administrator
Software Maintainer
Developer
Success-Critical Stakeholders
…
V&V Feedback
Usage Feedback
Execution Feedback
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 3
Neusoft DIMS Upgrade Project
• Document and Image Management System (DIMS) upgrade from version 6.0 to 7.0
• Change of database schema– add, remove or update DB attributes
• Change of database platforms– new capability of data migration
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 4
Initial Experiment of VBSQA Process Application
• Objective: Tailor VBSQA process framework to ERP software development in China
• Two week tutorials on VBSQA Process and WinWin Spiral Model– Developed a process instance composed of 22 ERP software
development activities6 misplaced activities due to misinterpretation 4 missing activities
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 5
Experience of Initial VBSQA Process Application
• Feedback from project managers of ERP solution providers– Shorten the new process learning curve– Maintain the flexibility of the process– Identify the flaws in a process instance– Tradeoffs among conflicting software Q-attributes– Determine stakeholders’ perspectives and
interaction points
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 6
Model VBSQA Process Using Object Petri Nets (OPN)• Inherit the merits of Petri Nets (PN)
– Formal semantics despite the graphical nature– State-based instead of event-based– Abundance of analysis techniques– Model concurrent process activities
• Support separation of concerns among various stakeholders’ perspectives– Object-oriented approach
– Model VBSQA Process Framework as the System Net (SN)
– Model each stakeholder’s process instance in a separate Object Net (ON)
Process activities in ONs are inherited from process steps/milestones in SN
– Interaction/negotiation among stakeholders and the SN/ON synchronization can be defined, analyzed, and integrated concurrently
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 7
Value-Based Process and OPN
System Net(VBSQA Process Framework)
Object Net(Stakeholder Process Instance)
Object Net(Stakeholder Process Instance)
…...
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 8
Formal Definitions of VBSQA-OPN• An OPN is a 3-tuple
– System Net: is a Petri Net with its tokens referring to Object Nets
– Object Nets: (n>1)
– SN and ONs synchronize via “channels” ρ• VBSQA-OPN =
– System Net: , VBSQA Process Framework or its tailoring
– Object Nets: (n>1) represents a set of process instances of stakeholders,
– Synchronization relation between SN and ONs:
, a mapping between VBSQA process framework steps/milestones and ERP software development activities.
– Guard functions: activation condition(s) of transitions
– Constraint 1: Inheritance of chronological order
– Constraint 2: Critical Path Dependency
),( , sONSNOPN
)( ,,21 n
ONONONON s
),,( WTPSN
),( , sONSN),,( WTPSN
),,( iiii FEBON )( ,,
21 nONONONON s
synsyn ET })1|{:( niEE isynsyn
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 9
OPN Notations
Elements Description Software Process Modeling
Place: current state (the marking) of a system; places contain tokens
Token: pre- or post- condition of firing a transition
Place: current state (the marking) of the System Net (VBSQA process framework) or an object net (a stakeholder’s process instance)
Token:
1) pre- or post- condition of activating a process step/milestone in System Net (SN) or an activity in Object Net (ON);
2) refer to an object net
Transition: events or actions which cause the change of system state
System Net: steps and milestones of VBSQA process framework or its tailoring
Object Net: activities of ERP software development
Arc: connects a place with a transition or a transition with a place
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 10
VBSQA-OPN System Net – VBSQA Process Framework
Mission objectives and stages
Project SCS classes & Business Cases
SCS define acceptable&desired
values for Q-attributes(γ)
Risk analysis & Architecture/technology evaluation
(δ)
Identify conflicting Q-attributes &
perform tradeoff analysis
(ε)
Deliverables:System top-level design and FRD
Architecture/technology
combination(s) CAN satisfy all Q-attribute
requirements?
Initiate project(α)
Project cost/benefit
analysis (β) Launch project
SCS adjust acceptable values for Q-attributes
(ζ)
Terminate or redefine project
Architecture/technology
combination(s) CANNOT satisfy all
Q-attribute requirements?
System top-level design
(η)
LCO Pass LCO Review (θ)(Exit criteria: Provide at
least one feasible architecture)
LCO Fail
LCO phase rework or extra work
(ι)
SCS: Success Critical Stakeholders
LCO: Life Cycle Objective
FRD: Feasibility Rationale Description
Q-: Qualitysynchronous transitions
status transitions
Legend (System Net)
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 11
Developer’s Object Net System Acquirer’s Object Net
VBSQA-OPN Object Nets – Stakeholders’ Process Instances
object-autonomous transitionssynchronous transitions
status transitionsLegend (Object Net)
Mission objectives and stages
Project SCS classes & Business Cases
Requirement elicitation meeting
(γ)
External prototype evaluation
(δ)
Identify conflicting Q-attributes &
perform tradeoff analysis
(ε)
Deliverables:System top-level design and FRD
Architecture/technology
combination(s) CAN satisfy all Q-attribute
requirements?
Acquire system upgrade
requirements(α)
Estimate system upgrade schedule/cost & develop DMR results chain
(β)
Schedule/cost accepted
Stakeholder renegotiation
(ζ)
Schedule/cost not accepted
Architecture/technology
combination(s) CANNOT satisfy all
Q-attribute requirements?
System top-level design
(η)
LCO Pass LCO Review (θ) (Exit criteria: Provide at
least one feasible architecture)
LCO Fail
LCO phase rework or extra work
(ι)
Developers
Peer review system top-level design & other documents
Mission objectives and stages
Project SCS classes & Business Cases
Requirement elicitation meeting
(γ)
External prototype evaluation
(δ)
Identify conflicting Q-attributes &
perform tradeoff analysis
(ε)Deliverables:
System top-level design and FRD
Architecture/technology
combination(s) CAN satisfy all Q-attribute
requirements?
Issue project bidding
(α)
Verify system upgrade
schedule/cost & DMR results
chain (β)
Launch project
Stakeholder renegotiation
(ζ)
Terminate or redefine project
Architecture/technology
combination(s) CANNOT satisfy all
Q-attribute requirements?
LCO Pass LCO Review (θ) (Exit criteria: Provide at
least one feasible architecture)
LCO Fail
System Acquirer
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 12
VBSQA Process Generator – Based on VBSQA-OPN Model
VBSQA Process Creator
VBSQA Process Checker
VBSQA Process
Simulator
A Mapping between ERP Software Development Activities
and VBSQA Process Framework
Simulation Results
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 13
VBSQA Process Creator– Map ERP Software Development Activities into VBSQA Process Framework
VBSQA Process Framework Steps/Milestones (System Net)
ERP Software Development Activities
(Object Nets)
Project cost/benefit analysis Estimate system upgrade cost & develop DMR results chain (Developer)
Verify system upgrade cost (System Acquirer)
SCS define acceptable & desired values for Q-attributes
Requirement elicitation meeting
Groupware WinWin negotiation
LCA Review Selected architecture internal review (Developer)
Selected architecture external review
CCD Internal core capability demo (Developer)
Onsite core capability demo
Objectives:• To shorten the VBSQA process learning curve • To reduce the flaws in generated process instances• To adapt to the changes in ERP software development activities
and/or workflows
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 14
VBSQA Process Creator – Creating an ERP VBSQA Process Instance
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 15
VBSQA Process Checker– Identifying the Flaws in a VBSQA Process Instance
• Maintain the flexibility of the process– Allow to remove a step in SN (VBSQA process framework)
Violate critical path activity dependencies due to missing activities
• VBSQA Process Checker– Formal properties defined in VBSQA-OPN System Net (SN) and
implemented in the VBSQA Process Checker
• Examples of the activity dependency constraints in the SN– SCS define acceptable & desired values for Q-attributes must be
completed before Risk analysis & architecture/technology evaluation– Risk analysis & architecture/technology evaluation must be completed
before System top-level design– System top-level design must be completed before LCO Review
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 16
VBSQA Process Simulator
• ROI of Synchronous Stakeholder Interaction Activities– ROI = (Value – Cost)/Cost– Value:
V: the total value of the project;
Eij (0-1): the effectiveness of a specific process activity on mitigating
the risk of Q-attribute i if it is performed in phase j;
Ri (0-1): the risk of Q-attribute i to the total value of the project.
– Cost = Activity Cost + Rework Cost
• Various combinations of synchronous stakeholder interaction activities and developer internal activities
m
i
n
jiij VREValue
1 1
)))1(1(((
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 17
VBSQA Process Simulator– ROI of Synchronous Stakeholder Interaction Activities
DIMS Top-Priority Q-attributes: Performance, Evolvability
Department of Computer Science and Engineering
Southern Methodist University
03/17/08 18
VBSQA Process Simulator– ROI of Synchronous Stakeholder Interaction Activities
ROI Process Activity Combinations Worst-Case
Scenario Best-Case Scenario
1 LCO(i)\ LCA(i) \ CCD(i) \ IOC(s) -0.223 —
2 LCO(s)\ LCA(i) \ CCD(i) \ IOC(s) -0.045 6.23
3 LCO(i)\ LCA(s) \ CCD(i) \ IOC(s) 0.162 2.414
4 LCO(i)\ LCA(i) \ CCD(s) \ IOC(s) -0.09 0.149
5 LCO(s)\ LCA(s) \ CCD(i) \ IOC(s) 0.194 6.165
6 LCO(s)\ LCA(i) \ CCD(s) \ IOC(s) 0.002 5.765
7 LCO(i)\ LCA(s) \ CCD(s) \ IOC(s) 0.205 2.33
8 LCO(s)\ LCA(s) \ CCD(s) \ IOC(s) 0.215 5.48
Department of Computer Science and Engineering
Southern Methodist University
Value/Petri Process Costs and Benefits
VBSQA-OPN Model ing Costs and Benefi ts
24
2 4 3
56
6 6
Many Hours!
0
10
20
30
40
50
60
70
80
90
100
Mutual Learning Developing Plan V&V of Pl an Improving Plan Earl y vs. LatePlan Rework
Hour
s
VBSQA-OPN Model ing Costs (hrs) VBSQA-OPN Model ing Benefi ts (Saved hrs)
Department of Computer Science and Engineering
Southern Methodist University
Process V&V
• Enforce the chronological order of process steps and milestones
• Identify the violation of critical path activity dependency
03/17/08 21
Department of Computer Science and Engineering
Southern Methodist University
Ambiguity Tolerance
• Process framework: steps, milestones and their order
– Process checker: defect identification
• Pre and post conditions – Process simulation
03/17/08 22
Department of Computer Science and Engineering
Southern Methodist University
Scalability
• Number of process steps: 12• Number of stakeholders/process instances: 4• Model cross-organizational processes
03/17/08 23
Department of Computer Science and Engineering
Southern Methodist University
Extensibility
• Need expertise on Petri-Nets in modeling new capabilities
03/17/08 24
Department of Computer Science and Engineering
Southern Methodist University
Flexibility
• Separation of concerns of different stakeholders/parties on the process
• Can add activities for individual process instance
• Support coordination among process instances
03/17/08 25
Department of Computer Science and Engineering
Southern Methodist University
Coverage• Process simulator
– estimate project schedule– estimate project budget– analyze quality attribute tradeoffs– optimize the project plan in terms of ROI– possible future extension: generate templates for
deliverables
• Model multi-views of processes• Model cross-organizational processes
03/17/08 26