IMPROVING PROGRAM COMPREHENSION TOOLS FOR DOMAIN-SPECIFIC LANGUAGES

Supervisors:

Professor Pedro Rangel Henriques

Professora Maria João Varanda Pereira

University of Minho, Department of Informatics

Nuno Oliveira

Imagine the following scenario:

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You are a software analyst…

…who is assigned a task of maintaining a software piece

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Well… this is just a part of that software…

void fn(){

struct model *o = (struct model *)malloc(sizeof(struct model));o->switch = true;while(o->switch){

try_sense(o);if(o->sensor_date != NULL){

o->p ++;o->h = 1;o->b = (struct object*)malloc(sizeof(struct object));o->b = o->sensor_date;o->sensor_date = NULL;o->b->next = NULL;

}}

}

Your first reaction…

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And this would be the second one…

- What does this program do?- What are its effects on the real world concepts?

- What is it all about?

- I Can’t even figure out the problem domain!

So you’d probably give up on maintaining such code.

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Robots are picking stones, but their

arms never go back down, after the first

stone!

Boss You

Ah, Ok! Let me see it

again.

But… what if, somehow, you have information about the problem domain?

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In fact, this code can solve a lot of problems, and none in particular

void fn(){

struct model *o = (struct model *)malloc(sizeof(struct model));o->switch = true;while(o->switch){

try_sense(o);if(o->sensor_date != NULL){

o->p ++;o->h = 1;o->b = (struct object*)malloc(sizeof(struct object));o->b = o->sensor_date;o->sensor_date = NULL;o->b->next = NULL;

}}

}

But if you know that this code corresponds to a robot task…

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Then…

Program Comprehension (PC) tools (PCTools) will fasten the way you work…

JIRiSS Imagix4D

DA4Java

CodeCrawlerCerberus

BauhausAlma

AlborzSeeSoft

Rigi

Reflexion Model

PICSSHriMP

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You will not be able to easily know what statement do what in the real world objects…

And…

Do not take advantage of Problem Domain

Do not connect Problem and Program Domains automatically

So…

Maintenance main tasks are still hand-made, increasing time and expenditures!

That is the HARDEST

part!!

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Brooks theorizes that:

A program is better understood if the person who is through the process of comprehension knows the program and problem domains, and is capable of establishing bridges between them.

To formalize such theory in a tool for General Purpose Languages (GPL) is impossible or, at least, is neither easy nor

direct!

Would it be the same with Domain-Specific Languages?

Why?

Well, imagine again the same scenario:

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You are a software analyst…

…who is assigned a task of maintaining a software piece

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… and that software was developed with a DSL:

PROGRAM {TURN_ONWHILE (TURNED_ON){

IF(HAS_STONE_IN_FRONT){ROBOT_ARM_ON;PICK_STONE;DROP_STONE_IN_BAG;

}}

}

Your first reaction…

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- What does this program do?- What are its effects on the real world concepts?

- Is that all?

- We’re talking about a robot task…- First, the robot is started, then, in a loop, it picks stones into a bag, whenever it senses one…

And this would be the second reaction…

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Do I need to tell you where the error is?

Boss You

No, boss! Already found it!

Yes, that was easy, but… what if

the DSL is more complex?

A PCTool improved to cope

with DSL advantages would

help us!Is it

possible?

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If we prove the following three things:

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Can the PC techniques, tailored for GPLs, be applied on DSLs?

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ALMA

- A system to assist program comprehension tasks for ANY GPL

DAST – Decorated Abstract Syntax Tree(ALMA internal representation (IR) )

The DAST stores the meaning of the program by using semantic patterns as nodes of a tree!

The Meaning?

TEC

HN

IQU

ES

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So, to cope with Problem Domain…

ALMA IR needs to be improved…

… adding on, to the semantic patterns:

represent the Problem Domain Concepts Actors

describe the behavior of the concepts according to the operational semantic of the program.

Animation Functions

Resulting in…

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represent the animation, at problem domain level, according to the operational semantic of the program

Animation Patterns

Are injected in the DAST, creating a DAPAST (Decorated with Animation Patterns Abstract Syntax Tree)

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The DAST technique was used in a PCTool

for GPLs…

Boss You

… and can be added of Animation Patterns to cope with Problem Domain Concepts!

Which are static for every

statement in a DSL, regardless of

the program…

So, this answers

question 1!

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Evolution: ALMA

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Evolution: ALMA >> ALMA2

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Beautiful… but how we specify a front-end for

ALMA2 ?

Boss

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1. Analyse DSL formal definition and its specific domain

DSL Formal Definition DSL Problem Domain

Program Domain ConceptsProblem Domain Concepts

Possible Internal State

Designing the Problem Visualization by Domains Analysis

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2. Define mappings between the problem concepts and syntactic or semantic parts of the DSL;

Program Domain Concepts Problem Domain Concepts

Conceptual Mappings Table

Designing the Problem Visualization by Concepts Mappings Definition

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3. Associate images or image sequences with concepts at problem domain;

Problem Domain Concepts Images

Behavioural Visualization Table

Designing the Problem Visualization by Images and Concepts Association

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4. Use Alma2 to build the mappings between problem and program domains and the imagery.

Conceptual Mappings Table Behavioural Visualization Table

Alma2 Front-End for DSPs

Designing the Problem Visualization by Definition of ALMA2 Specification

Theory is good, what about practice?

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rule Instruction_TurnLeft { INSTRUCTION ::= #Turnleft compute { INSTRUCTION.tree = new Alma.CStmtsNode( new AnimAssignNode( tA, new Alma.COperNode( new Alma.COperNode( new Alma.CVarNode(tA), new Alma.CConstNode(90), "+” ), new Alma.CConstNode(360), "%"), new AnimationPattern[] { new APRotate(robot, new int[] {1}, "angle"), new APLabel(robot, new int[] {1}, "beepers: ", "beepers") } ) ); }; }

=

a %

+ 360

a 90

Rotate

Label

For each grammar rule we define1. The Operational Semantics using ALMA2 basic API and2. The Operational Behaviour using ALMA2 extended API

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ALMA2 tested with Imperative DSL

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ALMA2 tested with Declarative DSL

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The improvement of ALMA to ALMA2 is

possible…

Boss You

… and the animation of the Problem Domain concepts

together with the visualization of program

domain, is a better perspective for the users!

We can only be sure of its

usefulness if we prove it…

Let’s prove it then!

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Extended Brooks TheoryA program comprehension tool, will ease the task of comprehending a program when synchronized visualizations of its program and problem domains are provided, since from these visualizations, the user is able to build a conceptual knowledge base that easily bridges both program and problem domains.

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The Proof Ingredients:

20 Participants 1 Questionnaire (8 Questions)

The Proof Objectives:

Compare variables measured both in Alma and Alma2

Solve PC tasks using Alma and Alma2

Measure variables with the questions:

Time (spent in the questions)Correctness (in the answers)Relevance assigned to the approach (of the synchronized visualizations)

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Time

Correctness

Relevance

The Proof Results:

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Despite of spending more time to create a mental model of

the program…

Boss You

So, maintenance

time and expenditures are reduced!

…With this approach, the

effectiveness of the

comprehension is achieved…Meaning that synchronized

Visualizations of Prog. And Prob. Domains

are important to achieve the

comprehension of the program

Conclusion

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Because the connection of both domains allows us

to:

Boss You

-Perceive how the program does;- Perceive what are the effects of the program in the problem domain…

Conclusion

And of course, to achieve knowledge through an

Action-Effect paradigm.

IMPROVING PROGRAM COMPREHENSION TOOLS FOR DOMAIN-SPECIFIC LANGUAGES

Thank you!!

University of Minho, Department of Informatics

Nuno Oliveira