Recommendation as Language Processing (RLP): A Unified Pretrain, Personalized Prompt & Predict Paradigm (P5) (2203.13366v7)

Abstract: For a long time, different recommendation tasks typically require designing task-specific architectures and training objectives. As a result, it is hard to transfer the learned knowledge and representations from one task to another, thus restricting the generalization ability of existing recommendation approaches, e.g., a sequential recommendation model can hardly be applied or transferred to a review generation method. To deal with such issues, considering that language can describe almost anything and language grounding is a powerful medium to represent various problems or tasks, we present a flexible and unified text-to-text paradigm called "Pretrain, Personalized Prompt, and Predict Paradigm" (P5) for recommendation, which unifies various recommendation tasks in a shared framework. In P5, all data such as user-item interactions, user descriptions, item metadata, and user reviews are converted to a common format -- natural language sequences. The rich information from natural language assists P5 to capture deeper semantics for personalization and recommendation. Specifically, P5 learns different tasks with the same LLMing objective during pretraining. Thus, it serves as the foundation model for various downstream recommendation tasks, allows easy integration with other modalities, and enables instruction-based recommendation based on prompts. P5 advances recommender systems from shallow model to deep model to big model, and will revolutionize the technical form of recommender systems towards universal recommendation engine. With adaptive personalized prompt for different users, P5 is able to make predictions in a zero-shot or few-shot manner and largely reduces the necessity for extensive fine-tuning. On several recommendation benchmarks, we conduct experiments to show the effectiveness of P5. We release the source code at https://github.com/jeykigung/P5.

A Unified Paradigm for Recommender Systems: Pretrain, Personalized Prompt, and Predict (P5)

In the rapidly evolving field of recommender systems, the traditional approach has been to develop task-specific models tailored to specific recommendation tasks. This fragmentation limits the transferability of knowledge across tasks and diminishes the generalization ability of these systems. Addressing this limitation, Geng et al. propose an innovative unified text-to-text paradigm for recommendation tasks, termed the "Pretrain, Personalized Prompt, and Predict Paradigm" (P5). This sophisticated framework integrates various recommendation tasks into a single, flexible architecture that leverages the power of NLP.

Contribution and Methodology

The central idea behind P5 is to harness the versatility of language to unify disparate recommendation tasks within a shared framework. The researchers construct inputs and targets as natural language sequences, transforming traditional recommendation data—such as user-item interactions, metadata, and reviews—into textual input. This design allows the model to pretrain on multiple tasks collectively, utilizing a common LLMing objective akin to techniques seen in advanced NLP models like T5 and GPT-3.

The personalized prompts, a defining feature of P5, encapsulate user and item descriptions in text form, allowing for richer semantics capture and more nuanced personalization. The pretraining stage of P5 employs instruction-based LLMing, where the model learns to understand personalized prompts by generating appropriate recommendations or responses. This mechanism equips P5 with strong zero-shot and few-shot capabilities, minimizing the dependence on extensive task-specific fine-tuning.

Experimental Validation

Geng et al. conducted rigorous experiments across several recommendation benchmarks, demonstrating that P5 not only matches but frequently surpasses the performance of state-of-the-art task-specific models. Here are some salient numerical results and key observations from the paper:

• Rating Prediction: P5 displayed impressive accuracy, closely aligning with Matrix Factorization (MF) on the RMSE metric while significantly outperforming it on MAE. This indicates a marked reduction in prediction error magnitudes.
• Sequential Recommendation: The model excelled with substantial improvements over established methods like SASRec and BERT4Rec. For instance, on the Beauty dataset, P5 achieved an HR@5 of 0.0508 in its base configuration, which was notably higher than the comparative S$^3$-Rec's HR@5 of 0.0387.
• Explanation Generation: Utilizing BLEU and ROUGE metrics, P5 demonstrated superior performance, particularly excelling in generating explanations that accurately captured user-item interactions and preferences.
• Review Summarization and Preference Prediction: P5 outperformed both T0 and GPT-2 models while employing significantly fewer parameters, showcasing effective summarization and preference prediction capabilities.

Implications and Future Directions

The proposed P5 paradigm marks a significant shift towards universal recommendation engines (URE) by embedding recommender systems deeply within the LLMing sphere. This convergence holds immense potential for advancing the personalization and scalability of recommendation engines. The unified framework simplifies the development pipeline, allowing for seamless integration of various tasks, which previously demanded individual models.

Moving forward, potential research directions include scaling P5 with even larger foundational models such as GPT-3, OPT, and BLOOM to explore the limits of this paradigm. There is also the promising avenue of extending P5 to encompass cross-modal applications, integrating visual, auditory, and textual data into a coherent recommendation framework. Moreover, the exploration of latent and retrieved-based prompts could enhance P5's ability to handle diverse and unstructured data, further refining the precision and context-awareness of generated recommendations.

Conclusion

The P5 paradigm by Geng et al. makes a compelling case for reimagining the technical foundation of recommender systems through the lens of natural language processing. By unifying various recommendation tasks into a single, adaptive text-to-text model, P5 stands poised to revolutionize the landscape of personalized recommendation, pushing towards a future where recommendation systems are not only more accurate but also more adaptable and integrated.

This comprehensive overview encapsulates the strengths and innovative aspects of the P5 framework, demonstrating its potential impact on recommender systems research and practice. The approach's ability to generalize across multiple tasks with minimal fine-tuning marks a significant advancement, setting the stage for further explorations in unified and instruction-based recommendation systems.