Representation Learning for Planning (RLeap)

Opportunities for PhD students and Postdoctoral researchers

Representation Learning for Planning (RLeap) is a project funded by the European Research Council; Advanced ERC Grant, Agreement: 885107, Years 2020-2025. PI is Hector Geffner; Blai Bonet is the other senior researcher fully engaged in this research.

The project and our participation in related projects like the EU funded TAILOR network (Trustworthy AI: Integrating Learning, Optimization and Reasoning), and the Swedish Wallenberg program in AI (WASP), are focused on a research problem that is at the heart of the current split in AI between data-based learners and model-based reasoners: the problem of learning symbolic first-order representations from raw perceptions.

Data-based learners, like those based on deep learning, are popular because there is plenty of data available, yet they produce black boxes that lack the flexibility, transparency, and guarantees of model-based systems. Building models by hand, on the other hand, it is just too hard.

By showing how to learn meaningful, symbolic models form raw perceptions, the research is aimed at integrating the benefits of data-based learners and model-based solvers in the context of planning, where representations play a key role in expressing, communicating, achieving, and recognizing goals. First-order symbolic representations refer to the representations based on objects and their relations.

The problem of representation learning for planning is largely unsolved. Two characteristics of deep reinforcement learning, one of the main approaches for learning how to act, are its ability to deal with high dimensional perceptual spaces without requiring any prior knowledge, combined with its inability to produce and re-use such knowledge. The construction of reusable knowledge (transfer learning) is a central concern in (deep) reinforcement learning, but the semantic and conceptual gap between the low level techniques that are used, and the high-level representations that are required, is just too large.

For addressing this challenge, new ideas and methods are required that will build on those of relevant areas that include planning, learning, knowledge representation, and combinatorial optimization. The approach to be the interpretations (grounding) of those representations, and it involves a number of subproblems like:

- learning  symbolic representations and their interpretation from raw perceptions (e.g., images)
- learning hierarchical symbolic representations to enable planning at different levels of abstraction:
- learning representations to explore, plan, and obtain and express general plans
- learning structure from suitable combinations of SAT and gradient-based methods
- understanding role of attention and partial observability in learning, grounding, and skill composition
- understanding the theoretical properties of representations and their relations to planning width

More about RLeap, can be found in the short and long version of the project proposals, and in this AAAI 2022 paper that can be regarded as 1-year report.

We are seeking highly motivated doctoral students and postdoctoral researchers eager to make a difference in these problems with experience in areas such as machine learning, planning, logic and knowledge representation, combinatorial optimization and SAT.

The doctoral students and postdoctoral researchers will pursue their research in the context of these broad goals, on specific themes that will be a function of their background, skills, and interests, and the needs of the project.

Ideal candidates should be able to do or learn to do theoretical and experimental work, logic and algorithms, programming and "differential programming" (deep learning), and (deep) reinforcement learning. Good oral and written skills in English are also required.

Interested PhD candidates should send a CV, transcripts, three reference letters, and a motivation statement to: Postdocs should send a CV, contact details of three references, and a research statement.

Hector is also a Wallenberg Guest Professor at Linköping University (LiU) within Swedish WASP program in AI, and there is also the possibility to be part of the project as a PhD student or postdoc at LiU with funding from WASP. The call and application procedure for those slots are posted periodically (lastest open call has application deadline 15/6/2022: PhD students and postdocs)