This document presents a new approach for using goal models to address the next release problem in requirements engineering. It proposes a goal-oriented language to capture the next release problem, formalizing the goal model and using an SMT solver to discover optimal solutions. Insights from a case study found the goal model structure helped provide an overview of requirements and theme-based layout was useful, while tool support needs improvement. The paper contributes a goal modeling language for the next release problem and a mapping of goal models to SMT formulas to find solutions, concluding more evaluation is needed and tool support should be enhanced.

1. The Next Release Problem Revisited:
A New Avenue for Goal Models
Fatma Ba¸sak Aydemir1
Fabiano Dalpiaz1
Sjaak Brinkkemper1
Paolo Giorgini2
John Mylopoulos3
1
Utrecht University
2
University of Trento
3
University of Ottawa
26th
IEEE International Requirements Engineering Conference

2. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 2 / 26

3. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 3 / 26

4. Goal Models in Requirements Engineering
RE most influential paper awards:
2006 [Ant96], 2007 [Yu97],
2011 [VL01], 2015 [GMMZ05]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 4 / 26

5. Goal Models in Requirements Engineering
RE most influential paper awards:
2006 [Ant96], 2007 [Yu97],
2011 [VL01], 2015 [GMMZ05]
Have been extended, integrated,
studied extensively [HAC+
17]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 4 / 26

6. Goal Models in Requirements Engineering
RE most influential paper awards:
2006 [Ant96], 2007 [Yu97],
2011 [VL01], 2015 [GMMZ05]
Have been extended, integrated,
studied extensively [HAC+
17]
Criticized as well, e.g., visual
scalability [MHM09]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 4 / 26

7. Goal Models in Requirements Engineering
RE most influential paper awards:
2006 [Ant96], 2007 [Yu97],
2011 [VL01], 2015 [GMMZ05]
Have been extended, integrated,
studied extensively [HAC+
17]
Criticized as well, e.g., visual
scalability [MHM09]
Ignored by the industry [MWT+
17]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 4 / 26

8. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 5 / 26

9. Visual scalability
Perception
Building, reading, and maintaining goal models is time consuming.
“Too much effort for the outcome” [MWT+
17]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 6 / 26

10. Visual scalability
Perception
Building, reading, and maintaining goal models is time consuming.
“Too much effort for the outcome” [MWT+
17]
Solutions
Iteration
Modularization [ACL+
10]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 6 / 26

11. Visual scalability
Perception
Building, reading, and maintaining goal models is time consuming.
“Too much effort for the outcome” [MWT+
17]
Solutions
Iteration
Modularization [ACL+
10]
. . . so, what is this new avenue?
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 6 / 26

12. Next Release Problem
Why may the next release problem be a good avenue?
Next release problem
The problem of selecting the optimal set of requirements to be
implemented for the next release of a software product based on
optimization objectives
Single objective [BRSW01]
Multi-objective [ZHM07]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 7 / 26

13. A New Avenue for Goal Models
The problem has an iterative nature
The initial goal model is extended over the life-span of the software
Reuse the model for release planning (beyond the next release)
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 8 / 26

14. A New Avenue for Goal Models
The problem has an iterative nature
The initial goal model is extended over the life-span of the software
Reuse the model for release planning (beyond the next release)
Requirements categories can be used to modularize the goal model
e.g., the goal model layout can be built to reflect the Scrum themes
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 8 / 26

15. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 9 / 26

16. Requirements Inter-dependencies for NRP [CSL+
01]
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 10 / 26

17. Requirements Inter-dependencies for NRP [CSL+
01]
⇓
Inter-dependency Meaning
REQUIRES R1 requires R2 to function
AND R1 requires R2 and vice versa
TEMPORAL R1 needs to be implemented before R2
CVALUE R1 positively or negatively contributes to the
customer value of R2
ICOST R1 positively or negatively contributes to the
cost of R2
OR Only one of {R1, R2} has to be implemented
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 10 / 26

18. Release Process: Create Goal Model
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 11 / 26

19. A Goal-Oriented Language for the Next Release Problem
Route plan for
single shipment
created
Production
synchronous
schedules created
Sales schedule
enhancements
provided
Credit card
processing
finalized
Fixed asset
enhancements
provided
Freight
management
Planned
A
financial
blocking
improved
execution and
financial handling
decoupled
Service and
maintenance
supported
C-
V+
Precedes
Load planning
conducted
Service and MaintenanceFreight Management
Goal
Refinement
Exclusion C+
Negative/Positive
Cost Contribution V+
Negative/Positive
Customer Value Contribution
Precedes
C- V-
Legend
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 12 / 26

20. Release Process: Adjust Constraints
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 13 / 26

21. Constraints and Optimization Scheme
Setting constraints
Cost and customer value for leaf goals
Absolute
Relative values from a scale
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 14 / 26

22. Constraints and Optimization Scheme
Setting constraints
Cost and customer value for leaf goals
Absolute
Relative values from a scale
Strength of cost and customer value
contribution
Route plan for
single shipment
created
Production
synchronous
schedules created
V+ 6
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 14 / 26

23. Constraints and Optimization Scheme
Setting constraints
Cost and customer value for leaf goals
Absolute
Relative values from a scale
Strength of cost and customer value
contribution
Constraints on solution
Budget, e.g., constraint on total cost
Minimal value that is acceptable
Mandatory and implemented goals
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 14 / 26

24. Constraints and Optimization Scheme
Choosing an optimization scheme
Many alternatives schemes exist:
Linear objective function
Maximize 0.6 ∗ V alue − 0.4 ∗ Cost
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 15 / 26

25. Constraints and Optimization Scheme
Choosing an optimization scheme
Many alternatives schemes exist:
Linear objective function
Maximize 0.6 ∗ V alue − 0.4 ∗ Cost
Lexicographic optimization
1. Minimize Cost
2. Maximize V alue
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 15 / 26

26. Constraints and Optimization Scheme
Choosing an optimization scheme
Many alternatives schemes exist:
Linear objective function
Maximize 0.6 ∗ V alue − 0.4 ∗ Cost
Lexicographic optimization
1. Minimize Cost
2. Maximize V alue
Pareto optimization
Maximize V alue
Minimize Cost
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 15 / 26

27. Release Process: Formalize Model
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 16 / 26

28. Formalize Models as Extended Constrained Goal Models
We transform NRP to optimization and satisfiability problem:
Baseline: Constrained Goal Models [NSGM18]
We extend CGMs with interdependencies
We automatically map the goal model to
satisfiability modulo theories clauses
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 17 / 26

29. Formalization
Intuition
Goals are literals
Mandatory goals are set to true
Refinements
A refinement is set to true if all of its children are true
A parent goal is true when any of its refinements are true
Cost and customer value contributions are true when both the
source and the target are true
. . .
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 18 / 26

30. Release Process: Optimize Solutions
Next release planningInitial set up
Step 1:
Create the
initial goal
model
Step 2: Adjust
constraints and
optimization
scheme
Step 3:
Formalize
the problem
Step 4:
Run
automated
solver
Reject solution/No solution
Analysis
results
Step 5:
Release
product
Accept Solution
Step 6: Update
the goal model
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 19 / 26

31. Optimizing the solutions
We rely on the OptiMathSAT [ST15] solver to discover the optimal
solutions
The solver can be iteratively called to explore the pareto front
The analyst checks the results, adjusts the model if necessary
The model is updated with each release
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 20 / 26

32. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 21 / 26

33. Insights from a case study
Context: a software product to manage heavy machinery
Freight
Management
improved
Data exchange with
freight requester
established
Enterprise
modeling mngt
relationships
visualized
Freight order
history
logged
Load
Planning
conducted
Route plan for
single shipment
created
Purchase and
sales
Contracts &
schedules
aligned
Cumulatives
(CUMs)
calculated
Production
synchronous
schedules created
Purchase
schedule
enhancements
provided
Sales schedule
enhancements
provided
Views on
schedules
created
Finance
Business unit
accounting
implemented
Cost controlling
enhancements
listed
Credit card
processing
finalized
German
topics list
created
Market
value report
generated
Fixed asset
enhancements
provided
FM
Planned
A
Se&Ma Depot
Repair
Item concepts
serialized
Financial
blocking
improved
Batch
repair
Call
management
integration
Contract
management
integration
Material
authorization
returned
Execution and
financial handling
decoupled
Se&Ma Depot
Repair and Sales
Invoicing
integrated
Service and
Maintenance
Transaction
logs kept
Business partner
calls transferred
Call
Management
Purchase/Sales
Enhancements
C-
V+
C+
Precedes
V+
C-
Precedes
Freight Management Purchase & Sales
Finance
Service and
Maintenance
Precedence
Goal
Refinement
Exclusion
C+
Negative/Positive
Cost Contribution
V+
Negative/Positive
Customer Value
Contribution
Precedes
C-
V-
Legend
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 22 / 26

34. Insights from a case study
Observations and comments from the involved product manager:
The goal model structure helped get an overview of the requirements
Theme-based layout of the model is useful for product managers
Analysis quickly answers what-if questions
Tool support is key. The prototype needs additional features, e.g.,
expanding/minimizing goals, zooming
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 23 / 26

35. Agenda
1. Goal Models in Requirements Engineering
2. A New Avenue for Goal Models
3. A Goal-Oriented Language for the Next Release Problem
4. Insights from a case study
5. Conclusions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 24 / 26

36. Conclusions and Future Work
Main take-away: NRP is a suitable problem for goal-oriented RE
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 25 / 26

37. Conclusions and Future Work
Main take-away: NRP is a suitable problem for goal-oriented RE
Contributions:
A goal modeling language to capture NRP
A mapping of the goal model into SMT formulas that allows using
an external SMT solver to discover optimal solutions
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 25 / 26

38. Conclusions and Future Work
Main take-away: NRP is a suitable problem for goal-oriented RE
Contributions:
A goal modeling language to capture NRP
A mapping of the goal model into SMT formulas that allows using
an external SMT solver to discover optimal solutions
Future work:
More empirical evaluation is necessary
Tool support should be enhanced to improve user experience
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 25 / 26

39. Contact us!
Fatma Ba¸sak Aydemir
f.b.aydemir@uu.nl
@aydemirfb
Fabiano Dalpiaz
f.dalpiaz@uu.nl
@FabianoDalpiaz
Thank you for your attention!
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 26 / 26

40. Metamodel
F. Dalpiaz (UU) The Next Release Problem Revisited:A New Avenue for Goal Models RE’18 1 / 5

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