What if your tools knew when
you have done a good job?
Jan Wloka,
PROLANGS
Rutgers University
Joint work with
Barbara G. Ryder Frank Tip
Virginia Tech IBM Research

What do tools know?
Our job is changing software systems
Using various kinds of tool support:
Process-aware Tools
Process
IDEs
Program
Behavior
Advanced Editors
Program
Structure
Text Editors
Resources
© Jan Wloka 2009 2

What do tools know?
Our job is changing software systems
Using various kinds of tool support:
Green bar:
“warm and fuzzy feeling”
© Jan Wloka 2009 2

Example: “I want smarter tools!”
Share local changes with team
Two “horror” scenarios:
1.Textual merge conflicts
2.Test failures after update
Very limited tool support:
Textual conflict detection
Change effects per file
Am I responsible?
© Jan Wloka 2009 3

Atomic Change Models
[PASTE’01, OOPSLA’04, ICSE’05, TSE’06, ICSE’09]
Decomposition into 19 distinct change kinds
Reflecting language semantics
All atomic: smaller ! merged, bigger ! grouped
Potential change in dispatch behavior
Lookup change: explicit effect on a dispatch entry
Inter-dependences between changes
structural:!syntax, containment, change groups
mapping:\" cause—effect
© Jan Wloka 2009 4

Explicit Representation of Change
Example: Additions to an empty class
Add
© Jan Wloka 2009 5

Explicit Representation of Change
Example: Additions to an empty class
Class
Counter
Field Method Method Method
sum Counter() getSum() inc()
Class
MultiCounter
Field Method Method
counters MultiCounter() inc()
Add
© Jan Wloka 2009 5

Explicit Representation of Change
Example: Additions to an empty class
Class
Counter
Field Method Method Method
sum Counter() getSum() inc()
Class
MultiCounter
Field Method Method
counters MultiCounter() inc()
Add AM4 AM1
AF3
CM5 CM2
© Jan Wloka 2009 5

Explicit Representation of Change
Example: Additions to an empty class
Class
Counter
Field Method Method Method
sum Counter() getSum() inc()
Class
MultiCounter
Field Method Method
counters MultiCounter() inc()
Add AM4 AM1
AF3
CM5 CM2
© Jan Wloka 2009 5

Explicit Representation of Change
Example: Additions to an empty class
Class
Counter
Field Method Method Method
sum Counter() getSum() inc()
CL7
Class
MultiCounter
Field Method Method
counters MultiCounter() inc()
Add AM4 AM1
AF3
CM5 CM2
CL6
© Jan Wloka 2009 5

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
P
I C
M M
AST :: edited
P
I C C
M M M M
© Jan Wloka 2009 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
AL
P
AL
I C
AC
M M
C
CL
AST :: edited
AM AM
M M
P
I C C
CM CM
M M M M
© Jan Wloka 2009 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
AL
call graph :: test1
P
AL
I C
AC
M M
C
CL
AST :: edited call graph :: test2
AM AM
M M
P
I C C
CM CM
M M M M
© Jan Wloka 2009 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
AL
call graph :: test1
P
AL
I C
AC
M M
C
Impact on
program behavior
CL
AST :: edited call graph :: test2
AM AM
M M
P
I C C
CM CM
M M M M
© Jan Wloka 2009 6

Classification of Change
I. Change of program elements: add / delete / change
Incl. declaration-level changes, e.g. type of class
II. Change of dynamic dispatch
Static type hierarchy ! changed method lookup
Structural vs. behavioral effects
III.Change of program behavior
Dynamic call graphs ! “exercised changes”
Affected tests and affecting changes
© Jan Wloka 2009 7

Example: Change-aware Unit
Testing
Yellow Bar: No
failures, but
untested changes!
Practical coverage
goal: 100%
changed behavior
More effective test
development
© Jan Wloka 2009 8

Example: Change-aware Process
Advisors
Advisors = explicit rules + tasks for guiding developers
Guard properties of development artifacts
Assist/automate tasks to satisfy properties
© Jan Wloka 2009 9

Example: Change-aware Process
Advisors
Advisors = explicit rules + tasks for guiding developers
Guard properties of development artifacts
Assist/automate tasks to satisfy properties
Change-aware rules, e.g., »Require Tests Pass«
Require test run to cover all changes
Require all affected tests pass
© Jan Wloka 2009 9

Example: Change-aware Process
Advisors
Advisors = explicit rules + tasks for guiding developers
Guard properties of development artifacts
Assist/automate tasks to satisfy properties
Change-aware rules, e.g., »Require Tests Pass«
Require test run to cover all changes
Require all affected tests pass
Assist for change delivery
Allow safely deliverable changes
Generate tests for changed but untested elements
© Jan Wloka 2009 9

Conclusions
Change models allow for reasoning about changes
Smarter tools aware of effects on structure + behavior
Known applications
Fault finding, Testing, Change delivery, Refactoring
A change-centric view on tools:
Process
Program
Behavior
Program
Structure
Resources
© Jan Wloka 2009 10

Conclusions
Change models allow for reasoning about changes
Smarter tools aware of effects on structure + behavior
Known applications
Fault finding, Testing, Change delivery, Refactoring
A change-centric view on tools:
Process
Program
Behavior
Program
Structure
Advanced Editors Resources
© Jan Wloka 2009 10

Conclusions
Change models allow for reasoning about changes
Smarter tools aware of effects on structure + behavior
Known applications
Fault finding, Testing, Change delivery, Refactoring
A change-centric view on tools:
Process
Program
Behavior
IDEs Program
Structure
Advanced Editors Resources
© Jan Wloka 2009 10

Conclusions
Change models allow for reasoning about changes
Smarter tools aware of effects on structure + behavior
Known applications
Fault finding, Testing, Change delivery, Refactoring
A change-centric view on tools:
Process
Change-aware Tools Program
Behavior
IDEs Program
Structure
Advanced Editors Resources
© Jan Wloka 2009 10

Conclusions
Change models allow for reasoning about changes
Smarter tools aware of effects on structure + behavior
Known applications
Fault finding, Testing, Change delivery, Refactoring
A change-centric view on tools:
Change-aware Process Advisors
Process
Change-aware Tools Program
Behavior
IDEs Program
Structure
Advanced Editors Resources
© Jan Wloka 2009 10