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Understanding software systems is hampered by their sheer size and complexity. Software visualization encodes the data found in these systems into pictures and enables the human eye to interpret it. In this lecture we present the concepts of software visualization and we show several examples of how visualizations can help in understanding software systems.
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Software in pictures
Tudor Gîrbawww.tudorgirba.com
Software is complex.
The Standish Group, 2004
53% Challenged
18% Failed
29% Succeeded
How large is your project?
How large is your project?
1’000’000 lines of code
How large is your project?
1’000’000 lines of code
* 2 = 2’000’000 seconds
How large is your project?
1’000’000 lines of code
* 2 = 2’000’000 seconds
/ 3600 = 560 hours
How large is your project?
1’000’000 lines of code
* 2 = 2’000’000 seconds
/ 3600 = 560 hours
/ 8 = 70 days
How large is your project?
1’000’000 lines of code
* 2 = 2’000’000 seconds
/ 3600 = 560 hours
/ 8 = 70 days
/ 20 = 3 months
forward engineering
actual development }
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forward engineering
actual development }
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
What are software metrics?
You cannot controlwhat you cannot measure.
Tom de Marco
Software metrics are measurements which
relate to software systems, processes or
related documents
Metrics compress the system into numbers.
Examples of size metrics
NOM - number of methods
NOA - number of attributes
LOC - number of lines of code
NOS - number of statements
NOC - number of children
Lorentz, Kidd, 1994Chidamber, 1994
McCabe, 1977
McCabe cyclomatic complexity counts the number of possible paths through the code of a function.
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
Queries reduce the analysis space.
Detection Strategies are metric-based queries to detect design flaws.
METRIC 1 > Threshold 1
Rule 1
METRIC 2 < Threshold 2
Rule 2
AND Quality problem
Lanza, Marinescu 2006
Example: a God Class centralizes too much intelligence in the system.
ATFD > FEW
Class uses directly more than a
few attributes of other classes
WMC ! VERY HIGH
Functional complexity of the
class is very high
TCC < ONE THIRD
Class cohesion is low
AND GodClass
Lanza, Marinescu 2006
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
Software in pictures
Tudor Gîrbawww.tudorgirba.com
1946
1956
1956
1956
1956 2006
1956 2006
1956 2006
?1956 2006
Visualization compresses the system into pictures.
1854,London,choleraepidemic
1854,London,choleraepidemic
A picture is worth
a thousand words.
UML took it literally :)
We are
visualbeings.
How many groups do you see?
How many groups do you see?
How many groups do you see?
How many groups do you see?
Gestalt principles
proximity
enclosure connectivity
similarity
More Gestalt principles
closure continuity
We are
visualbeings.
A picture is worth
a thousand words.
UML took it literally :)
Example: what is ?
Polymetric views show up to 5 metrics.
Color metric
Width metric
Height metric
Position metrics
Lanza, 2003
System Complexity shows class hierarchies.
lines
attributes
methods
Lanza, Ducasse, 2003
Class Blueprint shows class internals.
Initialize Interface Internal Accessor Attribute
invocation and access direction
Lanza, Ducasse, 2005
Class Blueprint has a rich vocabulary.
Regular
Overriding
Extending
Abstract
Constant
Delegating
Setter
Getter
Method
invocations
lines
Attribute
internal access
externalaccess
Access
Invocation
Class Blueprint shows class internals.
Distribution Map shows properties over structure. Ducasse etal, 2006
31 parts, 394 elements and 9 properties
Code City shows where your code lives.Wettel, Lanza, 2007
classes are buildings grouped in quarters of packages
Object Flow shows how objects move.Lienhard etal, 2007
objects flowing through other objects
forward engineering
actual development }
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Spectographs show change activity.Wu etal, 2004
commit
time
Evolution Matrix shows changes in classes.
Idle class
Pulsar class
Supernova class
White dwarf class
Lanza, Ducasse, 2002
Evolution Matrix shows changes in classes
What happens with inheritance?
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
History contains too much data.
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A
B B B B BC C C
D D D E
A is persistent, B is stable, C was removed, E is newborn ...
Hierarchy Evolution encapsulates time.
A
B
D
C
E
A is persistent, B is stable, C was removed, E is newborn ...
age
changedmethods
changedlines
Removed
Removed
Girba etal, 2005
Hierarchy Evolution reveals patterns.Girba etal, 2005
Evolution Radar shows co-change relationships.D’Ambros, Lanza 2006
one package and its co-change relationships
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
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McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
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{
McCabe = 21
LOC =
753,0
00NOM = 102
Metrics Queries Visualizations ...
But, what actually happens
behind the scene?
1 node type1 edge type3 metrics
3 node types2 edge types3 metrics 8 properties
System Complexity
Class Blueprint
A small experiment
1, 13, 27, 4, 96
What were the numbers?
Easy!
What was the last advertisement you saw?
Not so easy!
Each visualization provides a language that needs to be learnt.
So, what does happen
behind the scene?
Principle: Minimize chart junk
Tufte, 1990
Excel default
Excel default
Excel default+6 actions
Distribution Map shows properties.Ducasse etal, 2006
Tufte, 1990
Principle: Maximize data ink
Tufte, 1990
InfoBug is cute and condensed.Chuah, Eick, 2006
So, what does happen
behind the scene?
Example 1: CVS shows activity.
Who did this?
Alphabetical order is no order.
Ownership Map orders histories to reveal patterns. Girba etal, 2006
(john 23.06.03) public boolean stillValid (ToDoItem I, Designer dsgr) {(bill 09.01.05) if (!isActive()) {(bill 09.01.05) return false(bill 09.01.05) }(steve 16.02.05) List offs = i.getOffenders();(john 23.06.03) Object dm = offs.firstElement();(steve 16.02.05) ListSet newOffs = computeOffenders(dm);(john 23.06.03) boolean res = offs.equals(newOffs);(john 23.06.03) return res;
(george 13.02.05) public boolean stillValid (ToDoItem I, Designer dsgr) {(bill 11.13.05) if (!isActive()) {(bill 11.13.05) return false(bill 11.13.05) }(steve 16.02.05) List offs = i.getOffenders();(george 13.02.05) Object dm = offs.firstElement();(steve 16.02.05) ListSet newOffs = computeOffenders(dm);(george 13.02.05) boolean res = offs.equals(newOffs);(george 13.02.05) return res;
Example 2: Who copied from whom?
(john 23.06.03) public boolean stillValid (ToDoItem I, Designer dsgr) {(bill 09.01.05) if (!isActive()) {(bill 09.01.05) return false(bill 09.01.05) }(steve 16.02.05) List offs = i.getOffenders();(john 23.06.03) Object dm = offs.firstElement();(steve 16.02.05) ListSet newOffs = computeOffenders(dm);(john 23.06.03) boolean res = offs.equals(newOffs);(john 23.06.03) return res;
(george 13.02.05) public boolean stillValid (ToDoItem I, Designer dsgr) {(bill 11.13.05) if (!isActive()) {(bill 11.13.05) return false(bill 11.13.05) }(steve 16.02.05) List offs = i.getOffenders();(george 13.02.05) Object dm = offs.firstElement();(steve 16.02.05) ListSet newOffs = computeOffenders(dm);(george 13.02.05) boolean res = offs.equals(newOffs);(george 13.02.05) return res;
What is useless?
13.02.05 public boolean stillValid (ToDoItem I, Designer dsgr) {11.13.05 if (!isActive()) {11.13.05 return false11.13.05 }16.02.05 List offs = i.getOffenders();13.02.05 Object dm = offs.firstElement();16.02.05 ListSet newOffs = computeOffenders(dm);13.02.05 boolean res = offs.equals(newOffs);13.02.05 return res;
23.06.03 public boolean stillValid (ToDoItem I, Designer dsgr) {09.01.05 if (!isActive()) {09.01.05 return false09.01.05 }16.02.05 List offs = i.getOffenders();23.06.03 Object dm = offs.firstElement();16.02.05 ListSet newOffs = computeOffenders(dm);23.06.03 boolean res = offs.equals(newOffs);23.06.03 return res;
When did changes happen?
Clone Evolution shows how developers copy.Balint etal, 2006
Not every picture is worth a thousand words.
One more thing ...
Visualization is art, too.
Tudor Gîrbawww.tudorgirba.com
creativecommons.org/licenses/by/3.0/
