Adaptive ObjectOriented Software Development

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Adaptive Object-OrientedSoftware Development

• COM 3360

http//www.ccs.neu.edu/home/lieber/com3360/w03/w03
.html
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Introduction

• Software engineering, modeling, design, software
  architecture
• Programming languages
• Hands-on, practical, useful

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Summary of Course

• How to design and implement flexible
  object-oriented software using the principles of
  adaptiveness and separation of concerns in
  combination with UML and Java. Learning
  principles behind AspectJ and XML.
• How to design and implement flexible 100 pure
  Java software minimizing scattering and tangling
  of crosscutting behavioral concerns.

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Who is in Attendance?

• Software developers who have experience with
  object-oriented programming.
• Should know concepts of OOP, like classes,
  methods, and late binding.

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Academic Integrity

• Tension
• Learning from your peers is valuable
• for technical help this program does not run
  properly and I have tried for two hours to figure
  out why can I explain my program to you?
• for discussing ways to think about the concepts
• for project work if you work in a team of two
• for getting a concept explained
• for sharing frustrations
• Independent scholarship

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Academic Integrity

• Independent scholarship
• required for writing the homework solutions
• required for exams

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Important Rules

• Learn when to go inside and solve the problems
  yourself.
• Learn when it is appropriate to use help from a
  peer.
• Follow rules of handout.

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Featured in MIT Technology Magazine 2001 as a Top
Ten Technology
Agenda
Aspect-Oriented Progr. Adaptive Programming
DemeterJ Java and DJ Java environment UML XML
strategy graphs class graphs object graphs state
graphs
principles heuristics patterns idioms theorems alg
orithms
requirements domain analysis design implementation
use cases interfaces traversals visitors packages
Demeter Method iterative development spiral
model Extreme Programming
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Aspect-Oriented Software Development (AOSD)

• Observation many concerns of the
  designer/programmer are scattered across many
  classes or methods and tangled with code of other
  concerns.
• A concern is called crosscutting, if its ad-hoc
  implementation is scattered.
• AOSD is about cleanly modularizing crosscutting
  concerns. A modularized crosscutting concern is
  called an aspect.
• Reduces scattering and tangling.

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Agenda

• UML class diagrams. Perspective analysis,
  design, implementation
• Class graphs as special cases of UML class
  diagrams
• Textual representation of class graphs
• Default implementation of UML class diagrams as
  class graphs

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Agenda

• UML interaction diagrams
• sequence diagrams
• collaboration diagrams
• improving interaction diagrams to make them
  specification languages
• XML data type definitions and documents

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Agenda

• Class graphs in textual form (construction,
  alternation)
• object graphs (graphical and textual form)
• object graphs defined by class graphs
• add repetition classes and optional parts
• translating class graphs to Java

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Agenda

• annotating class graph with syntax class
  dictionary
• printing objects and language defined by class
  dictionary
• grammars, parsing, ambiguous grammars,
  undecidable problem
• LL(1) grammars, robustness of sentences
• etc.

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Overview

• good separation of concerns is the goal
• concerns should be cleanly localized
• programs should look like designs

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Adaptive Programming

• Programs adapt to interesting context changes
• Structure-shy behavior
• Succinct representation of traversals
• Programming in terms of graph constraints

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Cross-cutting of concerns
better program
ordinary program
structure-shy functionality
Components
structure
Aspect 1
synchronization
Aspect 2
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Modularization of crosscutting concerns
Instead of writing this
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Aspect-Oriented Programming
components and aspect descriptions
High-level view, implementation may be different
Source Code (tangled code)
weaver (compile- time)
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Examples of Aspects

• Collaborations, use cases
• Synchronization of methods across classes
• Remote invocation (using Java RMI)
• Quality of Service (QoS)
• Failure handling
• External use (e.g., being a Java bean)
• Replication, Migration

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Connections

• explain adaptive programming in terms of
  patterns
• Aspect-Oriented Programming (AOP) is a
  generalization of Adaptive Programming (AP)
• correspondence
• adaptive program object-oriented program
  sentence object graph

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Vocabulary

• Graph, nodes, edges, labels
• Class graph, construction, alternation
• Object graph, satisfying class graph
• UML class diagram
• Grammar, printing, parsing

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Vocabulary

• Traversals, visitors
• Strategy graphs, path set

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Overview this lecture

• Basic UML class diagrams
• Traversals/Collaborating classes
• Traversal strategy graphs
• Adaptive programming
• Tools for adaptive programming
• DemeterJ and AP/Studio

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1 Basic UML class diagrams

• Graph with nodes and directed edges and labels
  for nodes and edges
• Nodes classes, edges relationships
• labels class kind, edge kind, cardinality

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UML Class Diagram
busStops
BusRoute
BusStopList
buses
0..
BusStop
BusList
waiting
0..
passengers
Bus
PersonList
Person
0..
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2 Traversals / Collaborating classes

• To process objects we need to traverse them
• Traversal can be specified by a group of
  collaborating classes

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Collaborating Classes
use connectivity in class graph to define them
succinctly using strategy graphs
from Customer to Agent
from Company to Employee
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What's the problem? TANGLING
OOAD
Collab-1
C1
C4
C2
C3
C5
Collab-4
Collab-2
Collab-3
C1
C4
C2
C3
Implementation
C5
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Collaborating Classes
find all persons waiting at any bus stop on a bus
route
busStops
BusRoute
BusStopList
OO solution one method for each red class
buses
0..
BusStop
BusList
waiting
0..
passengers
Bus
PersonList
Person
0..
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3 Traversal Strategy Graphs

• Want to define traversals succinctly
• Use strategy graphs to express abstraction of
  class diagram
• Express traversal intent useful for
  documentation of object-oriented programs

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Traversal Strategy
find all persons waiting at any bus stop on a bus
route
first try from BusRoute to Person
busStops
BusRoute
BusStopList
buses
0..
BusStop
BusList
waiting
0..
passengers
Bus
PersonList
Person
0..
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Traversal Strategy
find all persons waiting at any bus stop on a bus
route
from BusRoute through BusStop to Person
busStops
BusRoute
BusStopList
buses
0..
BusStop
BusList
waiting
0..
passengers
Bus
PersonList
Person
0..
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Traversal Strategy
find all persons waiting at any bus stop on a bus
route
Altern. from BusRoute bypassing Bus to Person
busStops
BusRoute
BusStopList
buses
0..
BusStop
BusList
waiting
0..
passengers
Bus
PersonList
Person
0..
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Robustness of Strategy
find all persons waiting at any bus stop on a bus
route
from BusRoute through BusStop to Person
villages
BusRoute
BusStopList
busses
VillageList
busStops
0..
0..
BusStop
BusList
Village
waiting
0..
passengers
Bus
PersonList
Person
0..
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Filter out noise in class diagram

• only three out of seven classes
• are mentioned in traversal
• strategy!

from BusRoute through BusStop to Person
replaces traversal methods for the classes
BusRoute VillageList Village BusStopList
BusStop PersonList Person
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Why Traversal Strategies?

• Law of Demeter a method should talk only to its
  
• friends
• arguments and part objects (computed or
  stored)
• and newly created objects
• Dilemma
• Small method problem of OO (if followed) or
• Unmaintainable code (if not followed)
• Traversal strategies are the solution to this
  dilemma

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4 Adaptive Programming

• How can we use strategies to program?
• Need to do useful work besides traversing
  visitors
• Incremental behavior composition using visitors

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Styles of Adaptive Programming

• Traditional parameterize by class graph
  strategy is part of adaptive program
• Traditional optimized parameterize by class
  graph and strategy graph reuse pair of class
  graph and strategy graph.

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Writing Adaptive Programs with Strategies
(DJpure Java)
String WPSfrom BusRoute through BusStop to
Person
class BusRoute int countPersons(ClassGraph
cg) String WPSfrom BusRoute through
BusStop to Person Integer result
(Integer) cg.traverse(this, WPS, new
Visitor() int r public void before(Person
host) r public void start() r
0 public Object getReturnValue()
return new Integer ( r) )
return result.intValue()
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Writing Adaptive Programs with Strategies
(DJpure Java)
// Prepare the class graph ClassGraph classGraph
new ClassGraph() int r aBusRoute.countPerso
ns(classGraph)
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Goal of DJ

• Focus on crosscutting traversal-related concerns
  involve a group of collaborating objects which
  are manipulated to implement a behavior.
• Provide a Java library to cleanly encapsulate
  crosscutting traversal-related concerns whose ad
  hoc implementation would be scattered across many
  classes.

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Solves Open Problem in AOPfor Behavioral Aspects
in Java

• The ClassGraph-Aspect-Freezing problem
• When we have n behavioral aspects and the class
  graph changes, we potentially need to update all
  n aspects.
• DJ allows us to loosely couple behavioral aspects
  to the class graph.
• And this is all done in Java using REFLECTION.

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Writing Adaptive Programs with Strategies
(DJpure Java)
String WPStrategyfrom BusRoute through BusStop
to Person
class BusRoute int countPersons(TraversalGraph
WP) Integer result (Integer)
WP.traverse(this, new Visitor() int r
public void before(Person host) r
public void start() r 0 public
Object getReturnValue() return new
Integer ( r) ) return
result.intValue()
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Writing Adaptive Programs with Strategies
(DJpure Java)
String WPStrategyfrom BusRoute through BusStop
to Person
// Prepare the traversal for the current class
graph ClassGraph classGraph new
ClassGraph() TraversalGraph WPTraversal new
TraversalGraph (WPStrategy, classGraph) int
r aBusRoute.countPersons(WPTraversal)
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Writing Adaptive Programs with Strategies
(DJpure Java)
class Utility static int
countPersons(ObjectGraphSlice countSlice)
Integer result (Integer)
countSlice.traverse(new Visitor() int r
public void before(Person host) r
public void start() r 0 public
Object getReturnValue() return new
Integer ( r) ) return
result.intValue()
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Writing Adaptive Programs with Strategies
(DJpure Java)
String WPStrategyfrom BusRoute through BusStop
to Person
// Prepare the slice for the current class
graph ClassGraph classGraph new
ClassGraph() ObjectGraph objectGraph new
ObjectGraph(aBusRoute) ObjectGraphSlice
whatToCount new ObjectGraphSlice(objectGraph,
WPStrategy) int r Utility.countPersons(whatT
oCount)
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Writing Adaptive Programs with Strategies
(DemeterJ)
strategy from BusRoute through BusStop to Person
BusRoute int printCountWaitingPersons() //
traversal/visitor weaving through BusStop
to Person (PrintPersonVisitor)
PrintPersonVisitor before Person
PersonVisitor init r 0
THIS IS NOT JAVA
Extension of Java keywords init through
bypassing to before after etc.
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Writing Adaptive Programs with Strategies
(DemeterJ)
strategy from BusRoute through BusStop to Person
BusRoute traversal waitingPersons(PersonVis
itor) through BusStop to Person //
from is implicit int printCountWaitingPersons(
) // traversal/visitor weaving
waitingPersons(PrintPersonVisitor) PrintPersonVi
sitor before Person
PersonVisitor init r 0
THIS IS NOT JAVA
Extension of Java keywords traversal
init through bypassing to before after etc.
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Taxi driver analogy

• Streets and intersections correspond to class
  graph
• Traversal strategy determines how the taxi will
  navigate through the streets
• You can take pictures before and after
  intersections
• You can veto sub traversals

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Programming in Large Families
Two adaptive programs
A1
Class Graphs
A2
A1 family
Object-Oriented Programs
A2 family
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Adaptive Programming
Strategy
Bold names refer to DJ classes.
is use-case based abstraction of
ClassGraph
defines family of
ObjectGraph
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Adaptive Programming
Strategy
defines traversals of
ObjectGraph
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Adaptive Programming
Strategy
guides and informs
Visitor
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Strategies
BusRoute BusStop Person

• Nodes positive information Mark corner stones
  in class graph Overall topology
• of collaborating classes. 3 nodes
• from BusRoute
• through BusStop
• to Person

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Strategies
bypassing edges incident with Bus
BusRoute
Person
Edges negative information Delete edges from
class graph.
from BusRoute bypassing Bus to Person
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5 Tools for Adaptive Programming

• free and commercial tools available

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Free Tools on WWW

• DJ and AP Library
• Demeter/C
• DemeterJ
• Demeter/StKlos
• Dem/Perl5
• Dem/C
• Dem/CLOS
• Demeter/Object Pascal

last four developed outside our group
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Benefits of Adaptive Programming

• robustness to changes
• shorter programs
• design matches program
• more understandable code
• partially automated evolution
• keep all benefits of OO technology
• improved productivity

Applicable to design and documentation of your
current systems.
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DemeterJ
www.ccs.neu.edu/research/demeter

• class diagrams
• functionality
• strategies
• visitors
• etc.

Executable Java code for your favorite commercial
Java Software Development Environment
weaver
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DemeterJ in DemeterJ
structure (.cd) class diagrams
focus of this lecture
compiler/ weaver
structure-shy behavior (.beh) strategies
and visitors
structure-shy communication (.ridl) distribution
structure-shy object description (.input, at
runtime)
synchronization (.cool) multi threading
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Cross-cutting in DemeterJ
generated Java program
DemeterJ program
structure-shy functionality
structure
replicated!
synchronization
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AP Studio

• visual development of traversal strategies
  relative
• to class diagram
• visual feedback about collaborating classes
• visual development of annotated UML class diagrams

has not been used much
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Strengths of DemeterJ

• Theory
• Novel algorithms for strategies
• Formal semantics
• Correctness theorems
• Practice
• Extensive feedback (8 years)
• Reflective implementation

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Meeting the Needs

• DemeterJ
• Easier evolution of class diagrams (with strategy
  diagrams)
• Easier evolution of behavior (with visitors)
• Easier evolution of objects (with sentences)
• Better separation of crosscutting
  traversal-related concerns

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Real Life

• Used in several commercial projects
• Implemented by several independent developers
• Used in several courses, both academic and
  commercial

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Summary

• What has been learned Simple UML class diagrams,
  strategies and adaptive programs
• How can you apply
• DemeterJ takes adaptive programs as input
• Document and implement object-oriented programs
  with strategies using DJ in Java
• Design in terms of traversals and visitors

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Where to get more information

• Adaptive Programming book
• DJ home page
• DemeterJ home page
• Course home page
• www.ccs.neu.edu/research/demeter/

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Feedback

• Request feedback of training session