Timetable & Scheduling Engine

The Attendrix Scheduling Engine transforms institutional curricula, departmental batch assignments, and room capacities into a deterministic calendar of lecture slots.

1. Matrix Slot System & Academic Hierarchy

The scheduling system models academic schedules through a hierarchy of relational entities:

flowchart TD
    Sem["Semesters (Active Semester)"] --> Dept["Departments (CSE, ECE, ME)"]
    Dept --> Batch["Batches (e.g. CSE_2023)"]
    Batch --> BatchCourses["Batch Courses (Mandatory Core)"]
    Batch --> Electives["Elective Offering Semesters (Elective Pool)"]
    
    Slot["Slot Occurrences (Day-of-Week + Time Slot)"] --> Meetings["Course Meetings (Slot to Room Mapping)"]
    BatchCourses --> Meetings
    Electives --> Meetings
    
    Meetings --> Classes["Classes (Concrete Dated Instances)"]
    Overrides["Academic Calendar Overrides (Holidays, Day Shifts)"] --> Classes

Slot Identifiers

• Theory Lecture Slots: L1, L2, L3, L4, L5 (typically 50–60 minutes each).
• Practical Lab Slots: P1, P2, P3 (typically 110–120 minutes continuous blocks).
• Plus Slots: Dedicated supplemental slots for tutorial discussions or advanced problem-solving sessions (is_plus_slot = true).

2. Timetable Generation & Concurrency Locking

Batch schedule generation is performed by the database procedure generate_batch_schedule. Because regenerating a timetable touches thousands of slot occurrences across multiple tables, concurrent executions could introduce severe deadlocks or slot collisions.

Advisory Transaction Locks (pg_advisory_xact_lock)

To guarantee strict serializability without table locks:

-- Compute deterministic 64-bit lock key from batch_id and semester_id
SELECT pg_advisory_xact_lock(hashtext(p_batch_id || p_semester_id::text));

• Scope: The lock is scoped strictly to the current database transaction (xact).
• Zero Overhead: If a second administrator or process attempts to regenerate the schedule for the same batch simultaneously, it blocks cleanly until the active transaction commits or aborts.
• Granular Isolation: Different batches (e.g. CSE_2023 vs ECE_2024) generate schedules concurrently without contention.

3. Academic Calendar Overrides & Day Shifts

Universities regularly alter schedules to compensate for national holidays or academic festivals (e.g. "Wednesday follows Monday's timetable").

Attendrix handles timetable adjustments via public.academic_calendar_events and public.academic_calendar_overrides:

4. Extra Classes & Plus Slots

Faculty often schedule additional makeup lectures outside the regular weekly timetable.

• The schedule_class RPC allows instructors or student representatives to create ad-hoc occurrences.
• Flags: is_extra_class = true and optionally is_plus_slot = true.
• Conflict Detection: Checks existing active classes in the same batch and room for overlapping time ranges before inserting.