ros2-assignments/doc/architecture/interfaces/interfaces.md

ROS2 Interface Definitions - g2_2025_assign1_interfaces_pkg

Package Overview

This document describes the custom ROS2 interface definitions in the g2_2025_assign1_interfaces_pkg package. These interfaces provide standardized communication protocols for the TI Minor Grade Generator system.

Package Name: g2_2025_assign1_interfaces_pkg Interface Types: Messages, Services, Actions Location: src/g2_2025_assign1_interfaces_pkg/

Message Types (.msg)

Exam.msg

Represents examination result data exchanged between system components.

string student_name
string course_name
int32 result
builtin_interfaces/Time timestamp

Field Descriptions:

• student_name: Name identifier for the student
• course_name: Course identifier for the examination
• result: Numerical exam result/grade (integer value)
• timestamp: Timestamp of the message

Usage: Primary message type for exam result communication between ExamResultGenerator and grade processing nodes.

Student.msg

Represents student information and course enrollment data.

string student_name
string course_name
builtin_interfaces/Time timestamp

Field Descriptions:

• student_name: Name identifier for the student
• course_name: Course identifier for enrollment/management
• timestamp: Timestamp of the message

Usage: Used for student-course management operations and enrollment tracking.

Service Definitions (.srv)

Exams.srv

Service interface for grade calculation operations using multiple exam results.

Request

string student_name
string course_name
int32[] exam_grades

Response

int32 result  # Final calculated result

Request Fields:

• student_name: Student identifier for grade calculation
• course_name: Course identifier for context
• exam_grades: Array of exam grades to be processed

Response Fields:

• result: Final calculated grade result (integer value)

Usage: Main service interface used by GradeCalculator node for processing multiple exam grades into final results.

Action Definitions (.action)

Retake.action

Action interface for managing retake exam scheduling and processing workflows.

Goal

string student_name
string course_name

Result

float32 result

Feedback

string status

Goal Fields:

• student_name: Student for which a retake is requested
• course_name: Course for which a retake is requested

Result Field

• result: Progress indicator or intermediate result (float value) (Not Implemented)

Feedback Field:

• status: Status indicator (Not Implemented)

Usage: Used by RetakeScheduler node to handle long-running retake management operations with progress feedback.

Node Interface Usage

ExamResultGenerator Node

Publishers:

• Topic: exam_results
• Message Type: g2_2025_assign1_interfaces_pkg::msg::Exam
• Purpose: Publishes generated exam results to downstream processing nodes
• Rate: Configurable interval (default: 2 seconds)

Subscribers:

• Topic: student_course_management
• Message Type: g2_2025_assign1_interfaces_pkg::msg::Student
• Purpose: Receives student-course enrollment updates for exam generation queue

FinalGradeDeterminator Node

Subscribers:

• Topic: exam_results
• Message Type: g2_2025_assign1_interfaces_pkg::msg::Exam
• Purpose: Collects exam results for grade calculation processing

Service Clients:

• Service: calculate_grade
• Service Type: g2_2025_assign1_interfaces_pkg::srv::Exams
• Purpose: Requests grade calculation from GradeCalculator when threshold is met

Publishers:

• Topic: student_course_management
• Message Type: g2_2025_assign1_interfaces_pkg::msg::Student
• Purpose: Communicate end of enrollment when grade has been calculated

GradeCalculator Node

Service Servers:

• Service: calculate_grade
• Service Type: g2_2025_assign1_interfaces_pkg::srv::Exams
• Purpose: Provides grade calculation services for multiple exam grades
• Processing: Applies business logic (averaging, bonus points, validation)

RetakeScheduler Node

Action Servers:

• Action: retake_request
• Action Type: g2_2025_assign1_interfaces_pkg::action::Retake
• Purpose: Handles long-running retake scheduling operations
• Feedback: Provides progress updates during scheduling process

RetakeGradeDeterminator Node

Service Clients:

• Service: calculate_grade
• Service Type: g2_2025_assign1_interfaces_pkg::srv::Exams
• Purpose: Requests specialized retake grade calculations

Subscribers:

• Topic: retake_results
• Message Type: g2_2025_assign1_interfaces_pkg::msg::Exam
• Purpose: Processes completed retake exam results