Apr 16, 2010 - Andrew R. Dalton and William Kreahling. {adalton, wkreahling}@wcu.edu. Department of Mathematics and Computer Science. Western ...
Automated Construction of Memory Diagrams for Program Comprehension Andrew R. Dalton and William Kreahling {adalton, wkreahling}@wcu.edu Department of Mathematics and Computer Science Western Carolina University
April 16, 2010 ACM Southeast Conference
Andrew R. Dalton, Western Carolina University
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Presentation Roadmap
1
Introduction
2
System Overview
3
Toolkit Components
4
Examples
5
Conclusions and Questions
Andrew R. Dalton, Western Carolina University
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Introduction
Problems OO systems are complex Primitives vs references Instance vs class variables Instance vs class methods
Observation Visualizations help UML Memory diagrams
Creating visualizations by hand can be tedious
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Introduction (cont’d) Example ClassName ClassName private primitive 3
staticMethod()
private static reference
instanceMethod()
Idea A toolkit for automating the construction of memory diagrams will will help both students and instructors take advantage of memory diagrams as an aid to program comprehension. Andrew R. Dalton, Western Carolina University
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Contributions
Memory Diagramming Toolkit Java API Memory diagramming language (MDL) MDL to GXL translator GXL to MDL translator GXL to GraphViz DOT translator
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Presentation Roadmap
1
Introduction
2
System Overview
3
Toolkit Components
4
Examples
5
Conclusions and Questions
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Design Desiderata
Goals Enable creation of diagrams from correct programs Enable creation of incorrect diagrams Enable filtering of irrelevant details Enable cyclic diagram revision
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System Architecture
Toolkit Components Running Java Program
Java API
GXL2DOT
DOT File
GraphViz Dot
GXL File MDL File
MDL2GXL
GXL2MDL
Image
User
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Presentation Roadmap
1
Introduction
2
System Overview
3
Toolkit Components
4
Examples
5
Conclusions and Questions
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Java API Enables analysis of graph rooted at an object Uses reflection to recursively identify
Running Java Program
Classes Methods Fields Values
Java API
GXL File
Generates a GXL document Example 1 2 3 4 5
Map root = new HashMap(); root.put("Age", new Integer(18)); ... ObjectGraph graph = new ObjectGraph(root); graph.generateGxl(new File("mapGraph.gxl"));
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Memory Diagramming Language (MDL) Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
class Object { public String toString(); } class String extends Object { ... } class char[] extends Object { ... } class Person extends Object { primitive private static int personCount = 1; public static int getNumPeople(); public String getName(); public int getAge(); } object person instanceof Person { primitive private int age = 18; reference private String name = personName; } object personName instanceof String { reference private char[] value = charArray; } object charArray instanceof char[] { primitive public final int length = 3; primitive private char value[0] = ’J’; primitive private char value[1] = ’i’; primitive private char value[2] = ’m’; }
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MDL To GXL Translator
Uses compiler tools to scan and parse MDL files Builds an AST corresponding to the structure of the MDL file Applies the Visitor design pattern to traverse the AST and translate each element to GXL
Andrew R. Dalton, Western Carolina University
User
Running Java Program
MDL File
MDL2GXL
Java API
GXL File
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GXL To MDL Translator
Uses Java GXL library to load GXL document Traverses GXL graph and translates it to an in-memory model of the program Applies the Visitor design pattern to traverse the model and translate it to MDL
GXL File
GXL2MDL
MDL2GXL
MDL File User
Enables user to perform cyclic revisions to graphs
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GXL To Dot Translator
Translates GXL files to GraphViz Dot files Enables filtering Classes Methods Objects Fields
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GXL To Dot Translator (cont’d)
Like the GXL to MDL translator, loads GXL and builds a model Applies a different visitor to translate the model to Dot GraphViz Dot parses the Dot file and produces an image file
Andrew R. Dalton, Western Carolina University
GXL File
GXL2DOT
Image
Other Toolkit Components
DOT File
GraphViz Dot
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Presentation Roadmap
1
Introduction
2
System Overview
3
Toolkit Components
4
Examples
5
Conclusions and Questions
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Strings
String::toUpperCase() String::substring(int) String::toLowerCase() String::length() String::trim() String::intern()
String int count 3 char[] value
char[] int length
length
3
Object::toString() char [0] W
char [1] C
Andrew R. Dalton, Western Carolina University
char [2] U
array
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Enumerations
Direction Direction EAST
Direction ordinal() name()
EAST
Direction NORTH Direction SOUTH
NORTH
values() valueOf(String)
Direction WEST
SOUTH
WEST
Direction
Direction
int ordinal
int ordinal
int ordinal
2
3
0
Direction int ordinal 1
String name
String name
String name
String name
...
...
...
...
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Linked List contains(Object) clear() add(Object) get(int) add(int, Object) set(int, Object) size() remove(Object) indexOf(Object)
LinkedList int size 4 LinkedList$ListNode head LinkedList$ListNode tail
LinkedList$ListNode Object element
LinkedList$ListNode next
LinkedList this$0
LinkedList$ListNode Object element
LinkedList$ListNode next
Integer
LinkedList this$0
LinkedList$ListNode
int value
Object element
LinkedList$ListNode next
LinkedList this$0
0
Integer intValue()
int value
LinkedList$ListNode Object element
LinkedList$ListNode next
LinkedList this$0
1
Integer int value
LinkedList$ListNode Object element
LinkedList$ListNode next
LinkedList this$0
2
Integer int value 3
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Incorrect (By Design)
getValue() setValue(Integer) toString()
int Integer value 27
int
MDL Code 1 2 3 4 5 6
class Object { public String toString(); } class int extends Object { public Integer getValue(); public void setValue(Integer value); } object object0 instanceof int { primitive private Integer value = 27; }
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Presentation Roadmap
1
Introduction
2
System Overview
3
Toolkit Components
4
Examples
5
Conclusions and Questions
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Conclusions Contribution: Memory Diagramming Toolkit Java API Memory diagramming language (MDL) MDL to GXL translator GXL to MDL translator GXL to GraphViz DOT translator Enables Creation of diagrams from correct programs Creation of incorrect diagrams Filtering of irrelevant details Cyclic diagram revision
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Future Directions
More student use and feedback Enhance selection GUI to enable element highlighting Expand approach to other OO languages
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Automated Construction of Memory Diagrams for Program Comprehension Andrew R. Dalton and William Kreahling {adalton, wkreahling}@wcu.edu Department of Mathematics and Computer Science Western Carolina University
April 16, 2010 ACM Southeast Conference
Questions?
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