TOOLS USA '99

Interaction Schemata:Compiling Interactions to Code

Neeraj Sangal, Edward Farrell,Tendril Software, Inc,

Westford, MAhttp://www.tendril.com

Karl Lieberherr, and David H. LorenzCollege of Computer Science

Northeastern UniversityBoston, MA 02115

Northeastern University

Outline Motivation

Generate Code From Interaction Diagrams

The Problem Diagrams are not precise

Concept Formulization Interaction Schemata

Two Implementation Approaches Code generation approach

Structure Builder (SB) Generative approach

DJ (Demeter Java)

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Motivation: Round Trip

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Interactions Diagrams

// Class: Library// File: Library.java/** * (c) Northeastern University * @param book * @author dl * @SBGen Generated Method (2) */void upwardTransportationExample(Book book) {// SBgen: Calls generated method on Book (2)SBObject sbsecondUser = new SBObject();User firstUser = book.getNextUser(sbsecondUser);User secondUser = (User)sbsecondUser.getValue();// SBgen: End Call

// SBgen: Action Execute method on User (5)firstUser.notifyBookReady();

// SBgen: Action Execute method on User (6)secondUser.alertYouAreNext();}

// Class: Book// File: Book.java/** @SBGen Generated Method (4), created by Library.up(Book) (Library.2,-2) */User getNextUser(SBObject sbsecondUser) {// SBgen: Action Execute method on Book (3)User firstUser = getFirstUser();// SBgen: Action Execute method on Book (4)

Goal: Generating Code From Interaction Diagrams

Goal: Generating Code From Interaction Diagrams

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The Problem Problem

UML interaction diagrams are not precise enough to prescribe code.

UML interaction diagrams are difficult to keep up-to-date with the code.

Solution Approaches Code generation approach

Structure Builder: A Java design tool Method generated with mark-ups

Generic approach DJ: A research project Interactive traversals using JGL and Reflection

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What's Missing in Interaction Diagrams

No object "book-keeping" Ignores scope and visibility issues Ignores object transportation issues Other details: method parameters, return types,

collections to iterate over, etc.

Sub-Goal: Make Interaction Diagrams Complete

Sub-Goal: Make Interaction Diagrams Complete

Code Generation Approach:

Structure Builder (SB)

Generative Approach:

DJ (Demeter Java)

and then

or

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Association

Role

Class

Example: Library System

Cardinality

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Where did user come from?

Object "Book-Keeping" Library.checkIn(Copy copy, UID uid)

What is the signature of removeCopy?

Generated methods must have correct signature and return type.

Generated methods must have correct signature and return type.

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What is the scope of book?

Scope and Visibility

book is out of scope!

Objects have scope even in Interaction Diagrams

Objects have scope even in Interaction Diagrams

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Where did copy come from?

Downward Object Transportation

copy must be transported down through removeCopy()

copy must be transported down through removeCopy()

Returned by findCopy()

Used by release()

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Where did resUser come from?

Upward Object Transportation

Generated by getFirstOnReservationList()

Called for notifyBookReady()

resUser must be transported up through getNextUser()

resUser must be transported up through getNextUser()

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Object Transportation - Wrapper

firstUser and secondUser have to be transported up through getNextUser()

Second object is passed back through a wrapper.

Second object is passed back through a wrapper.

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Textual Representation Nested Methods

a.m1() {b.m2()

}

Conditional

if (test) {a.m1();

}

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Formalization of Actions Syntax for actions

[interactor interactor ...].actionName(exp1,exp2,...) return(type1 retexp1, type2 retexp2,...) {...}

Basic actions Method call

Conditional

Iteration

Additional predefined actions on collections Find

Add

Remove

User defined actions Anything

Can contain other actionsThe scope of each returned

variable is limited to being inside the innermost enclosing conditional or iterative action.

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Sequence Diagram for CheckIn

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Interaction Schema for CheckInLibrary.checkIn(UID uid, Copy copyId) { [libraryusersuid].find(uid'current == uid) return (User users'current as theUser)

[theUserborrowscopyId].remove(copyId'current == copyId) return (Copy borrows'current as theCopy)

[theCopy].getBook() return (Book book as theBook)

[theBookreserves].remove(reserves'index == 0) return (User reserves'current as theReserver)

if (theReserver != null) { [theReserverholds].add(theCopy)

[theReserver].notify(theCopy); }}

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Interactions Involve Multiple Classes

C1

C2 C3

C4

C5

Interact-1

Interact-2 Interact-3Interact-4

C1

C2 C3

C4

C5

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void checkIn(UID uid, Copy copyId){ User user = null; Object tmpKey; Enumeration i = users.keys(); while(i.hasMoreElements()) { tmpKey = i.nextElement(); user = (User)users.get(tmpKey); if (user.uid==uid) break; } Copy copy = user.checkIn(copyId); Book book = copy.getBook(); User resUser = book.checkIn(); if (resUser != null) { resUser.checkIn0(copy); resUser.notify(copy); }}

User checkIn(){ User resUser = null; int size = reserves.size(); if (size > 0) { resUser = reserves.elementAt(0); reserves.removeElementAt(0); }

return resUser;}

Copy checkIn(Copy copyId){ Copy copy = null; int i, size = borrows.size(); for (i=size-1; i>=0; i--) { Copy tmpVar = (Copy)borrows.elementAt(i); if (tmpVar.getId() == copyId) { copy = tmpVar; borrows.removeElementAt(i); break; } return copy; }

void checkIn0(Copy copy){ holds.addElement(copy);}

Method generated in class Library

class User

class Book

Method Generation Approach Four methods generated in

three classes Library User Book

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StructureBuilder Approach: Generated Method Dialog

Actions

Action Properties

Available Objects

Action on Selected Object

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Object Transportation

firstUser.notifyBookReady()is missing information: red color indicates a problem

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Object Transportation

User links the missing information: firstUser

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DJ Approach Build on Demeter/Java experience

AP Library, visitor organization Create class graph from Java programs Generalized traversals: find, add, ...

Name traversals new TravSpec("From Library to User").container(this));

Compute traversals dynamically Container c = new TraversalGraph(Main.classGraph,

new TravSpec(…));

Main observation Actions like add, find, and delete appear in Generic Programming

(GP) as methods of container interfaces (e.g., JGL). DJ attempts to reuse those generic algorithms.

Better to have an easy-to-use less-powerful

system than a harder-to-use more-powerful

system.

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The checkIn Method in DJvoid checkIn(UID uid, Copy copyId){

Container LibraryToUserContainer = new TraversalGraph( Main.classGraph, new TravSpec("From Library to User").container(this));User user = Finding.findIf( LibraryToUserContainer, new FieldEquals("uid",uid));if (user == null) return;Container UserToCopyContainer = new TraversalGraph( Main.classGraph, new TravSpec("From User through borrows to Copy").container(user));Copy copy = Finding.findIf( UserToCopyContainer, new FieldEquals("copyId",copyId));if (copy == null) return;Removing.remove(UserToCopyContainer,copy);Container CopyToUser = new TraversalGraph (…) ;Container UserToCopyHoldsCont = new TraversalGraph( Main.classGraph, new TravSpec("From User through holds to Copy").container(user));User reserver = (User)CopyToUser.remove(CopyToUser.elements());if (reserver != null) {

UserToCopyHoldsCont.add(copy);reserver.notify(copy);

}}

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Conclusions Possible to generate code from interaction diagrams.

Interactions must be made complete. Possible to preserve simplicity of interaction diagrams and

yet make them complete.

Interaction diagrams can be made adaptive by addition of traversal semantics.

Actions allow programmers to try out different types of data structures in a structure-shy manner.

Diagrams like programs need to deal with basic programming issues like scope, visibility, and transportation.

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Future Combine the two approaches. Domain specific action types. Improved object caching techniques. Suggestions for changes to internal data structures for

improved performance.

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Additional Information StructureBuilder @ Tendtril Software

Free product evaluation download www.tendril.com

DJ @ Northeastern University Download papers and source code www.ccs.neu.edu/research/demeter

The End

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Code for Transporting One Object Up

// Class: Library// File: Library.java/** * (c) Northeastern University * @param book * @author dl * @SBGen Generated Method (2) */void up(Book book) {

// Call generated method on Book (2)User firstUser = book.getNextUser();// Action Execute method on User (5)firstUser.notifyBookReady();

}

// Class: Book// File: Book.java/** @SBGen Generated Method (4) */User getNextUser() {

// Action Execute method on Book (3)User firstUser = getFirstUser();// Return firstUserreturn (firstUser);

}

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Generated Code for Upward Transportation of Two Objects

// Class: Library

// File: Library.java

/**

* (c) Northeastern University

* @param book

* @author David Lorenz

* @SBGen Generated Method (2)

*/

void upwardTransportationExample(Book book) {

// SBgen: Calls generated method on Book (2)

SBObject sbsecondUser = new SBObject();

User firstUser = book.getNextUser(sbsecondUser);

User secondUser = (User)sbsecondUser.getValue();

// SBgen: End Call

// SBgen: Action Execute method on User (5)

firstUser.notifyBookReady();

// SBgen: Action Execute method on User (6)

secondUser.alertYouAreNext();

}

// Class: Book

// File: Book.java

/** @SBGen Generated Method (4), created by Library.up(Book) (Library.2,-2) */

User getNextUser(SBObject sbsecondUser) {

// SBgen: Action Execute method on Book (3)

User firstUser = getFirstUser();

// SBgen: Action Execute method on Book (4)

User secondUser = getSecondUser;

// SBgen: Returns firstUser

sbsecondUser.setValue(secondUser);

return firstUser;

// SBgen: End Return

}