Department of Computer Science and Engineering Southern Methodist University 03/17/081 LiGuo Huang [email protected] Department of Computer Science

Department of Computer Science and Engineering

Southern Methodist University

03/17/08 1

LiGuo [email protected]

Department of Computer Science & Engineering


Modeling Value-Based Process with Object Petri-Nets



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



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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



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



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



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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



03/17/08 7

Value-Based Process and OPN

System Net(VBSQA Process Framework)

Object Net(Stakeholder Process Instance)

Object Net(Stakeholder Process Instance)

…...



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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



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



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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


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)



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Developer’s Object Net System Acquirer’s Object Net

VBSQA-OPN Object Nets – Stakeholders’ Process Instances

object-autonomous transitionssynchronous transitions

status transitionsLegend (Object Net)



Requirement elicitation meeting

(γ)

External prototype evaluation

(δ)



(ε)

Deliverables:System top-level design and FRD



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




System top-level design

(η)

LCO Pass LCO Review (θ) (Exit criteria: Provide at


LCO Fail

LCO phase rework or extra work

(ι)

Developers

Peer review system top-level design & other documents




(γ)

External prototype evaluation

(δ)



(ε)Deliverables:

System top-level design and FRD



requirements?

Issue project bidding

(α)

Verify system upgrade

schedule/cost & DMR results

chain (β)

Launch project

Stakeholder renegotiation

(ζ)

Terminate or redefine project




LCO Pass LCO Review (θ) (Exit criteria: Provide at


LCO Fail

System Acquirer



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



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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


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



03/17/08 14

VBSQA Process Creator – Creating an ERP VBSQA Process Instance



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



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(((



03/17/08 17

VBSQA Process Simulator– ROI of Synchronous Stakeholder Interaction Activities

DIMS Top-Priority Q-attributes: Performance, Evolvability



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



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)



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Discussion



Process V&V

• Enforce the chronological order of process steps and milestones

• Identify the violation of critical path activity dependency

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Ambiguity Tolerance

• Process framework: steps, milestones and their order

– Process checker: defect identification

• Pre and post conditions – Process simulation

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Scalability

• Number of process steps: 12• Number of stakeholders/process instances: 4• Model cross-organizational processes

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Extensibility

• Need expertise on Petri-Nets in modeling new capabilities

03/17/08 24



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



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



Dynamism

• Defect introduction and removal

03/17/08 27

Documents

Department of Computer Science and Engineering Southern Methodist University 03/17/081 LiGuo Huang [email protected] Department of Computer Science