合久必分，分久必合Long union must separate, long separation must unite

Discovering aspects from requirements goal models

Yijun Yu1

Julio C. S. P. Leite2

John Mylopoulos1

Identify Aspects Early on in the Software Development Process

Our Goal:

Our Result:

Aspects can be discovered during goal oriented requirements

analysis

3

Overview

1. Early Requirements in AOP paradigm1.1 Design Principles in AOP

1.2 Requirements Goal Models

2. Aspect discovery through construction of a V-graph (goals, softgoals, and tasks)

3. A case study: Media Shop+osCommerce

4. Summary

4

1. Principles1.1 Increase Fan-in, aka. DRY

• “Whenever possible, we wish to maximize fan-in during the design process. Fan-in is the raison d’être (grounds for existence) of modularity. Each instance of multiple fan-in means that some duplicate code has been avoided.” (Yourdon, Constantine, Structured Design p. 172, 1979)

• The DRY principle: Don’t Repeat Yourself[A. Hunt, and D. Thomas. Pragmatic Programmer. Addison Wesley,1999. in (Martin Fowler, Avoid Repetition, IEEE Software, Jan/Feb 2001 pp.97—99.)]

5

CCC

C

CC

C

AspectC

IOC

DRY

6

VALUE

REMOVALL

MOVE UNTIL

FIND

STRINGCOMP

SCAN

Yourdon & Constantine, SD, pg.168

FIND: AT LINE 5

VALUE: AT LINE7

SCAN: AT LINE 15

MOVE UNTIL: AT LINE 8

REMOVALL: AT LINE 2

7

Stan Wagon’s bikeMy square-wheel bike, on permanent display at Macalester College. This construction, believe it or not, earned me an entry in "Ripley's Believe It or Not"; beats standing in a block of ice for three days or growing three-foot long fingernails.

-- http://www.stanwagon.com

Stan Wagon (wagon@macalester.edu), Prof. of Mathematics and Computer Science, Macalester College, St. Paul, Minnesota

8Yourdon & Constantine, SD, pg.168

VALUE

REMOVALL

MOVE UNTIL

FIND

STRINGCOMP

SCAN

FIND: AT LINE 5

VALUE: AT LINE7

SCAN: AT LINE 15

MOVE UNTIL: AT LINE 8

REMOVALL: AT LINE 2

The Weaver

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AspectJ

aspect Logging {

pointcut NeedLogging(): call(void FIND()) || call(void MOVEUNTIL()) || call(void REMOVALL) || call(void SCAN() || call(void VALUE());

after() returning: NeedLogging() { STRINGCOMP(); }}

advice

aspect

pointcut

The GROUND

The WAGON

The DRIVER

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1.2 Requirements Goal Models

• A goal model is an intentional model• A goal can be decomposed into AND or OR

subgoals• A goal model has both hard and soft goals

– A hard goal can be either satisfied or denied– A soft goal is partially satisfied => satisficed

• Soft goal uses HELP (+), HURT (-), MAKE (++) or BREAK (--) correlations to show partial satisfaction (satisfice) from a set of subgoals

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1.2.1 Hard goal model

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1.2.2 Soft goal model

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T: satisfiedF: deniedU: unknown

Text Editor SMTP

AND

Get Reliable Reply

Get Reliable Reply

FS: Fully satisfiedPS: Partially satisfiedUN: UnknownPD: Partially deniedFD: Fully deniedCF: ConflictGoal:

Contact a Friend

Goal:Email a Friend

Goal:Mail a Friend

Goal:Call a Friend

++: MAKE

+: HELP --: BREAKOR

++: MAKE

Goal-Oriented Requirements Analysis

14

T: satisfiedF: deniedU: unknown

Text Editor SMTP

AND

Get Reliable Reply

Get Reliable Reply

FS: Fully satisficedPS: Partially satisficedUN: UnknownPD: Partially deniedFD: Fully deniedCF: ConflictGoal:

Contact a Friend

Goal:Email a Friend

Goal:Mail a Friend

Goal:Call a Friend

OR

++: MAKE

++: MAKE

+: HELP --: BREAK

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V-graph

In order to reason about interplay of functional and non-functional requirements, we create a particular type of goal model, called V-graph

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Goal

Task

SoftgoalSoftgoal

cont

ribut

ion

cont

ribut

ion

correlation

V

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2. The Process– Start from root-level goals and soft goals, correlate

and decompose them into a V-graph– A goal analysis based on the label propagation

algorithm is used to check for:• Conflicts• Inconsistencies• Denial of any goal or soft goals

– After resolving the problems, a proper V-graph is obtained

– Then we list the candidate aspects from the V-graph

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Consistent

tasks

goals softgoals

goals softgoals

tasks

root goal

softgoals

list objectives

No conflict

goals softgoals

tasks

listaspects

V model

aspects

Satisfied & satisficed

correlation

decompose

softgoalssoftgoals

correlate

decompose

resolve conflict

decompose

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3. A Case Study• Medi@Shop adapted from literature:

Castro, Kolp, Mylopoulos, Towards requirements-driven information systems engineering: the Tropos project, Journal of Information Systems, 2002. Can we find aspects from early requirements?

• osCommerce studied from an LAMP (Linux, Apache, MySQL, PHP) Open-Source project: (http://www.oscommerce.com) Do they manifest in the developed software?

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osCommerce (version 2.2m2)

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Candidate aspects in the codeClone detection (by Semantic Design,Inc)

LOC #clones Code description Need refactoring?

1 319 require($path . $file); No

1 260 echo $expression; No

559 2 class email; No

2 292 define ($variable, $value); No

76 2 class mime; No

4 67 messageStack->add ($error); Yes (NFR)

15 15 Postal code zone check Yes (FR)

22 10 require(application_top.php);SSL check

Yes (FR/NFR)

3 64 Set HTML head CHARSET Yes (NFR)

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Consistent

tasks

goals softgoals

goals softgoals

tasks

root goal

softgoals

list objectives

No conflict

goals softgoals

tasks

listaspects

V model

aspects

Satisfied & satisficed

correlation

decompose

softgoalssoftgoals

correlate

decompose

resolve conflict

decompose

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Correlate initial goals and softgoals

T1T0

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Inconsistent decomposition

T1 T2

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T3

Resolving inconsistency

T2

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Further decomposition

T3 T4

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Further…

T5

29T6

30T7

Resolving Conflicts

T6

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Result candidate aspects

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Goal Aspects

goal aspect Responsiveness[transaction] {pointcut transaction(): Preparing[cart,product]) ||

CheckingOut[cart, product, account, stock]); required () by: transaction() { SessionCookie[transaction](); }};• AspectJ-like syntax• Allow weaving the operationalized tasks with goals

specified in the pointcut

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aspects

goals softgoals

tasks

Separatingaspects

V graph

pointcutsaspects

advicetasks

functiontasks

goals

weaving

Goal aspects

4. SUMMARY

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5. On-going and future work

1. On Implementations:– Weaving the goal aspects– AspectPHP: adapting the Zend PHP interpretator– AspecT*: testing NFR in the weaved code

2. Another case study: CORBA

3. Extensions– From V-graph to agent-oriented frameworks such

as i* and KAOS– reuse of goal aspects