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: 1 You are a software analyst… …who is assigned a task of maintaining a software piece

2 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… 3 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.

4 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?

5 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…

6 Then… Program Comprehension (PC) tools (PCTools) will fasten the way you work… JIRiSS Imagix4D DA4Java CodeCrawler Cerberus Bauhaus Alma Alborz SeeSoft Rigi Reflexion Model PICS SHriMP

7 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!!

8 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: 9 You are a software analyst… …who is assigned a task of maintaining a software piece

10 … and that software was developed with a DSL: PROGRAM { TURN_ON WHILE (TURNED_ON){ IF(HAS_STONE_IN_FRONT){ ROBOT_ARM_ON; PICK_STONE; DROP_STONE_IN_BAG; }

Your first reaction… 11 - 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…

12 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?

13 If we prove the following three things:

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

15 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? TECHNIQUES

16 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…

17 represent the animation, at problem domain level, according to the operational semantic of the program Animation Patterns Are injected in the DAST, creating a D AP AST (Decorated with Animation Patterns Abstract Syntax Tree)

18 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!

19

20 Evolution: ALMA

21 Evolution: ALMA >> ALMA 2

22 Beautiful… but how we specify a front-end for ALMA2 ? Boss

23 1. Analyse DSL formal definition and its specific domain DSL Formal Definition DSL Problem Domain Program Domain Concepts Problem Domain Concepts Possible Internal State Designing the Problem Visualization by Domains Analysis

24 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

25 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

26 4. Use Alma 2 to build the mappings between problem and program domains and the imagery. Conceptual Mappings Table Behavioural Visualization Table Alma 2 Front-End for DSPs Designing the Problem Visualization by Definition of ALMA2 Specification Theory is good, what about practice?

27 rule Instruction_TurnLeft { INSTRUCTION ::= #Turnleft compute { INSTRUCTION.tree = new Alma.CStmtsNode( new AnimAssignNode( tA, 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 % a 90 Rotate Label For each grammar rule we define 1. The Operational Semantics using ALMA2 basic API and 2. The Operational Behaviour using ALMA2 extended API

28 ALMA 2 tested with Imperative DSL

29 ALMA 2 tested with Declarative DSL

30 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!

31 Extended Brooks Theory A 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. Extended Brooks Theory A 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.

32 The Proof Ingredients: 20 Participants 1 Questionnaire (8 Questions) The Proof Objectives: Compare variables measured both in Alma and Alma 2 Solve PC tasks using Alma and Alma 2 Measure variables with the questions: Time (spent in the questions) Correctness (in the answers) Relevance assigned to the approach (of the synchronized visualizations)

33 Time Correctness Relevance The Proof Results:

34 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

35 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