Dual Vector RAG AI TOEFL Writing Assistant
An AI-powered writing evaluator built for a WPI IQP project, combining semantic embedding and algorithmic vectorization with RAG to grade TOEFL/IELTS essays against real rubrics.
Project Details / Background
This WPI IQP project involved developing an AI-powered writing assistant for TOEFL/IELTS preparation, working with a Chinese educational company (comparable to Google Classroom) to design and implement a prototype system for evaluating student writing. The core idea combines semantic-based embedding and algorithmic-based vectorization with retrieval-augmented generation (RAG) to assist a large language model in evaluating essays. The system ingests an essay, generates two distinct performance vectors (one LLM-based and embedded, another algorithmically derived using error counters), then retrieves relevant exemplar essays using the RAG before generating scored feedback.
I single-handedly designed and implemented the writing evaluation portion of the system, including the RAG architecture, the document ingestion pipeline, database management, and API integration. The system scores essays across four TOEFL dimensions: task response, coherence and cohesion, lexical resource, and grammatical range and accuracy. The full project was published in a WPI group report, linked below.
Read the full published report: digital.wpi.edu
System Architecture
Overall RAG pipeline: vectorize, retrieve similar essays, grade
Algorithmic vector: grammar error metrics pipeline
LLM-embedded vector: semantic grammar description pipeline
Output / Demo
Grader output: scored feedback across all four TOEFL dimensions
"Ask the Tutor" follow-up chat for essay feedback