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Siddharth Srivastava

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35 papers
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35

AAAI Conference 2026 Conference Paper

Context-Sensitive Abstractions for Reinforcement Learning with Parameterized Actions

  • Rashmeet Kaur Nayyar
  • Naman Shah
  • Siddharth Srivastava

Real-world sequential decision-making often involves parameterized action spaces that require both, decisions regarding discrete actions and decisions about continuous action parameters governing how an action is executed. Existing approaches exhibit severe limitations in this setting---planning methods demand hand-crafted action models, and standard reinforcement learning (RL) algorithms are designed for either discrete or continuous actions but not both, and the few RL methods that handle parameterized actions typically rely on domain-specific engineering and fail to exploit the latent structure of these spaces. This paper extends the scope of RL algorithms to long-horizon, sparse-reward settings with parameterized actions by enabling agents to autonomously learn both state and action abstractions online. We introduce algorithms that progressively refine these abstractions during learning, increasing fine-grained detail in the critical regions of the state–action space where greater resolution improves performance. Across several continuous-state, parameterized-action domains, our abstraction-driven approach enables TD(λ) to achieve markedly higher sample efficiency than state-of-the-art baselines.

PRL Workshop 2025 Workshop Paper

AI Planning: A Primer and Survey (Preliminary Report)

  • Dillon Ze Chen
  • Pulkit Verma
  • Siddharth Srivastava
  • Michael Katz
  • Sylvie Thiebaux

Automated decision-making is a fundamental topic that spans multiple sub-disciplines in AI: reinforcement learning (RL), AI planning (AP), foundation models, and operations research, among others. Despite recent efforts to “bridge the gaps” between these communities, there remain many insights that have not yet transcended the boundaries. Our goal in this paper is to provide a brief and non-exhaustive primer on ideas well-known in AP, but less so in other subdisciplines. We do so by introducing the classical AP problem and representation, and extensions that handle uncertainty and time through the Markov Decision Process formalism. Next, we survey state-of-the-art techniques and ideas for solving AP problems, focusing on their ability to exploit problem structure. Lastly, we cover subfields within AP for learning structure from unstructured inputs and learning to generalise to unseen scenarios and situations.

AAAI Conference 2025 Conference Paper

Autonomous Option Invention for Continual Hierarchical Reinforcement Learning and Planning

  • Rashmeet Kaur Nayyar
  • Siddharth Srivastava

Abstraction is key to scaling up reinforcement learning (RL). However, autonomously learning abstract state and action representations to enable transfer and generalization remains a challenging open problem. This paper presents a novel approach for inventing, representing, and utilizing options, which represent temporally extended behaviors, in continual RL settings. Our approach addresses streams of stochastic problems characterized by long horizons, sparse rewards, and unknown transition and reward functions. Our approach continually learns and maintains an interpretable state abstraction, and uses it to invent high-level options with abstract symbolic representations. These options meet three key desiderata: (1) composability for solving tasks effectively with lookahead planning, (2) reusability across problem instances for minimizing the need for relearning, and (3) mutual independence for reducing interference among options. Our main contributions are approaches for continually learning transferable, generalizable options with symbolic representations, and for integrating search techniques with RL to efficiently plan over these learned options to solve new problems. Empirical results demonstrate that the resulting approach effectively learns and transfers abstract knowledge across problem instances, achieving superior sample efficiency compared to state-of-the-art methods.

AIJ Journal 2025 Journal Article

Explain it as simple as possible, but no simpler – Explanation via model simplification for addressing inferential gap

  • Sarath Sreedharan
  • Siddharth Srivastava
  • Subbarao Kambhampati

One of the core challenges of explaining decisions made by modern AI systems is the need to address the potential gap in the inferential capabilities of the system generating the decision and the user trying to make sense of it. This inferential capability gap becomes even more critical when it comes to explaining sequential decisions. While there have been some isolated efforts at developing explanation methods suited for complex decision-making settings, most of these current efforts are limited in scope. In this paper, we introduce a general framework for generating explanations in the presence of inferential capability gaps. A framework that is grounded in the generation of simplified representations of the agent model through the application of a sequence of model simplifying transformations. This framework not only allows us to develop an extremely general explanation generation algorithm, but we see that many of the existing works in this direction could be seen as specific instantiations of our more general method. While the ideas presented in this paper are general enough to be applied to any decision-making framework, we will focus on instantiating the framework in the context of stochastic planning problems. As a part of this instantiation, we will also provide an exhaustive characterization of explanatory queries and an analysis of various classes of applicable transformations. We will evaluate the effectiveness of transformation-based explanations through both synthetic experiments and user studies.

IJCAI Conference 2025 Conference Paper

Explain It as Simple as Possible, but No Simpler – Explanation via Model Simplification for Addressing Inferential Gap (Abstract Reprint)

  • Sarath Sreedharan
  • Siddharth Srivastava
  • Subbarao Kambhampati

One of the core challenges of explaining decisions made by modern AI systems is the need to address the potential gap in the inferential capabilities of the system generating the decision and the user trying to make sense of it. This inferential capability gap becomes even more critical when it comes to explaining sequential decisions. While there have been some isolated efforts at developing explanation methods suited for complex decision-making settings, most of these current efforts are limited in scope. In this paper, we introduce a general framework for generating explanations in the presence of inferential capability gaps. A framework that is grounded in the generation of simplified representations of the agent model through the application of a sequence of model simplifying transformations. This framework not only allows us to develop an extremely general explanation generation algorithm, but we see that many of the existing works in this direction could be seen as specific instantiations of our more general method. While the ideas presented in this paper are general enough to be applied to any decision-making framework, we will focus on instantiating the framework in the context of stochastic planning problems. As a part of this instantiation, we will also provide an exhaustive characterization of explanatory queries and an analysis of various classes of applicable transformations. We will evaluate the effectiveness of transformation-based explanations through both synthetic experiments and user studies.

NeurIPS Conference 2024 Conference Paper

Belief-State Query Policies for User-Aligned POMDPs

  • Daniel Bramblett
  • Siddharth Srivastava

Planning in real-world settings often entails addressing partial observability while aligning with users' requirements. We present a novel framework for expressing users' constraints and preferences about agent behavior in a partially observable setting using parameterized belief-state query (BSQ) policies in the setting of goal-oriented partially observable Markov decision processes (gPOMDPs). We present the first formal analysis of such constraints and prove that while the expected cost function of a parameterized BSQ policy w. r. t its parameters is not convex, it is piecewise constant and yields an implicit discrete parameter search space that is finite for finite horizons. This theoretical result leads to novel algorithms that optimize gPOMDP agent behavior with guaranteed user alignment. Analysis proves that our algorithms converge to the optimal user-aligned behavior in the limit. Empirical results show that parameterized BSQ policies provide a computationally feasible approach for user-aligned planning in partially observable settings.

IJCAI Conference 2024 Conference Paper

Hierarchical Decompositions and Termination Analysis for Generalized Planning (Abstract Reprint)

  • Siddharth Srivastava

This paper presents new methods for analyzing and evaluating generalized plans that can solve broad classes of related planning problems. Although synthesis and learning of generalized plans has been a longstanding goal in AI, it remains challenging due to fun- damental gaps in methods for analyzing the scope and utility of a given generalized plan. This paper addresses these gaps by developing a new conceptual framework along with proof techniques and algorithmic processes for assessing termination and goal-reachability related properties of generalized plans. We build upon classic results from graph theory to decompose generalized plans into smaller components that are then used to derive hi- erarchical termination arguments. These methods can be used to determine the utility of a given generalized plan, as well as to guide the synthesis and learning processes for generalized plans. We present theoretical as well as empirical results illustrating the scope of this new approach. Our analysis shows that this approach significantly extends the class of generalized plans that can be assessed automatically, thereby reducing barriers in the synthesis and learning of reliable generalized plans.

AAAI Conference 2024 Conference Paper

Hierarchical Planning and Learning for Robots in Stochastic Settings Using Zero-Shot Option Invention

  • Naman Shah
  • Siddharth Srivastava

This paper addresses the problem of inventing and using hierarchical representations for stochastic robot-planning problems. Rather than using hand-coded state or action representations as input, it presents new methods for learning how to create a high-level action representation for long-horizon, sparse reward robot planning problems in stochastic settings with unknown dynamics. After training, this system yields a robot-specific but environment independent planning system. Given new problem instances in unseen stochastic environments, it first creates zero-shot options (without any experience on the new environment) with dense pseudo-rewards and then uses them to solve the input problem in a hierarchical planning and refinement process. Theoretical results identify sufficient conditions for completeness of the presented approach. Extensive empirical analysis shows that even in settings that go beyond these sufficient conditions, this approach convincingly outperforms baselines by 2x in terms of solution time with orders of magnitude improvement in solution quality.

NeurIPS Conference 2023 Conference Paper

Autonomous Capability Assessment of Sequential Decision-Making Systems in Stochastic Settings

  • Pulkit Verma
  • Rushang Karia
  • Siddharth Srivastava

It is essential for users to understand what their AI systems can and can't do in order to use them safely. However, the problem of enabling users to assess AI systems with sequential decision-making (SDM) capabilities is relatively understudied. This paper presents a new approach for modeling the capabilities of black-box AI systems that can plan and act, along with the possible effects and requirements for executing those capabilities in stochastic settings. We present an active-learning approach that can effectively interact with a black-box SDM system and learn an interpretable probabilistic model describing its capabilities. Theoretical analysis of the approach identifies the conditions under which the learning process is guaranteed to converge to the correct model of the agent; empirical evaluations on different agents and simulated scenarios show that this approach is few-shot generalizable and can effectively describe the capabilities of arbitrary black-box SDM agents in a sample-efficient manner.

JAIR Journal 2023 Journal Article

Hierarchical Decompositions and Termination Analysis for Generalized Planning

  • Siddharth Srivastava

This paper presents new methods for analyzing and evaluating generalized plans that can solve broad classes of related planning problems. Although synthesis and learning of generalized plans has been a longstanding goal in AI, it remains challenging due to fundamental gaps in methods for analyzing the scope and utility of a given generalized plan. This paper addresses these gaps by developing a new conceptual framework along with proof techniques and algorithmic processes for assessing termination and goal-reachability related properties of generalized plans. We build upon classic results from graph theory to decompose generalized plans into smaller components that are then used to derive hierarchical termination arguments. These methods can be used to determine the utility of a given generalized plan, as well as to guide the synthesis and learning processes for generalized plans. We present theoretical as well as empirical results illustrating the scope of this new approach. Our analysis shows that this approach significantly extends the class of generalized plans that can be assessed automatically, thereby reducing barriers in the synthesis and learning of reliable generalized plans.

PRL Workshop 2023 Workshop Paper

Learning to Create Abstraction Hierarchies for Motion Planning under Uncertainty

  • Naman Shah
  • Siddharth Srivastava

State and action hierarchies have been found to be invaluable in long-horizon robot motion planning. However, approaches for learning such hierarchies tend to require extensive experience on the target task, target environment and/or deterministic dynamics. This paper considers the problem of learning how to create state and action abstractions for a known robot with stochastic low-level controllers in previously unseen environments. We present a novel and robust approach for learning to create an abstract, searchable state space, high-level options, as well as low-level option policies in this setting. We show that this approach facilitates efficient hierarchical planning in stochastic settings with strong guarantees of composability and completeness for holonomic robots. Extensive empirical analysis with holonomic as well as non-holonomic robots on a total of $60$ different combinations unseen environments and tasks shows that the resulting approach is broadly applicable, scales well and enables effective learning and transfer even in tasks with long horizons where baselines are unable to learn.

AAAI Conference 2022 Conference Paper

Differential Assessment of Black-Box AI Agents

  • Rashmeet Kaur Nayyar
  • Pulkit Verma
  • Siddharth Srivastava

Much of the research on learning symbolic models of AI agents focuses on agents with stationary models. This assumption fails to hold in settings where the agent’s capabilities may change as a result of learning, adaptation, or other post-deployment modifications. Efficient assessment of agents in such settings is critical for learning the true capabilities of an AI system and for ensuring its safe usage. In this work, we propose a novel approach to differentially assess black-box AI agents that have drifted from their previously known models. As a starting point, we consider the fully observable and deterministic setting. We leverage sparse observations of the drifted agent’s current behavior and knowledge of its initial model to generate an active querying policy that selectively queries the agent and computes an updated model of its functionality. Empirical evaluation shows that our approach is much more efficient than re-learning the agent model from scratch. We also show that the cost of differential assessment using our method is proportional to the amount of drift in the agent’s functionality.

KR Conference 2022 Conference Paper

Discovering User-Interpretable Capabilities of Black-Box Planning Agents

  • Pulkit Verma
  • Shashank Rao Marpally
  • Siddharth Srivastava

Several approaches have been developed for answering users' specific questions about AI behavior and for assessing their core functionality in terms of primitive executable actions. However, the problem of summarizing an AI agent's broad capabilities for a user is comparatively new. This paper presents an algorithm for discovering from scratch the suite of high-level "capabilities" that an AI system with arbitrary internal planning algorithms/policies can perform. It computes conditions describing the applicability and effects of these capabilities in user-interpretable terms. Starting from a set of user-interpretable state properties, an AI agent, and a simulator that the agent can interact with, our algorithm returns a set of high-level capabilities with their parameterized descriptions. Empirical evaluation on several game-based scenarios shows that this approach efficiently learns descriptions of various types of AI agents in deterministic, fully observable settings. User studies show that such descriptions are easier to understand and reason with than the agent's primitive actions.

AAMAS Conference 2022 Conference Paper

JEDAI: A System for Skill-Aligned Explainable Robot Planning

  • Naman Shah
  • Pulkit Verma
  • Trevor Angle
  • Siddharth Srivastava

This paper presents JEDAI, an AI system designed for outreach and educational efforts aimed at non-AI experts. JEDAI features a novel synthesis of research ideas from integrated task and motion planning and explainable AI. JEDAI helps users create high-level, intuitive plans while ensuring that they will be executable by the robot. It also provides users customized explanations about errors and helps improve their understanding of AI planning as well as the limits and capabilities of the underlying robot system.

NeurIPS Conference 2022 Conference Paper

Learning Generalized Policy Automata for Relational Stochastic Shortest Path Problems

  • Rushang Karia
  • Rashmeet Kaur Nayyar
  • Siddharth Srivastava

Several goal-oriented problems in the real-world can be naturally expressed as Stochastic Shortest Path problems (SSPs). However, the computational complexity of solving SSPs makes finding solutions to even moderately sized problems intractable. State-of-the-art SSP solvers are unable to learn generalized solutions or policies that would solve multiple problem instances with different object names and/or quantities. This paper presents an approach for learning \emph{Generalized Policy Automata} (GPA): non-deterministic partial policies that can be used to catalyze the solution process. GPAs are learned using relational, feature-based abstractions, which makes them applicable on broad classes of related problems with different object names and quantities. Theoretical analysis of this approach shows that it guarantees completeness and hierarchical optimality. Empirical analysis shows that this approach effectively learns broadly applicable policy knowledge in a few-shot fashion and significantly outperforms state-of-the-art SSP solvers on test problems whose object counts are far greater than those used during training.

PRL Workshop 2022 Workshop Paper

Relational Abstractions for Generalized Reinforcement Learning on Symbolic Problems

  • Rushang Karia
  • Siddharth Srivastava

Reinforcement learning in problems with symbolic state spaces is challenging due to the need for reasoning over long horizons. This paper presents a new approach that utilizes relational abstractions in conjunction with deep learning to learn a generalizable Q-function for such problems. The learned Q-function can be efficiently transferred to related problems that have different object names and object quantities, and thus, entirely different state spaces. We show that the learned, generalized Qfunction can be utilized for zero-shot transfer to related problems without an explicit, hand-coded curriculum. Empirical evaluations on a range of problems show that our method facilitates efficient zeroshot transfer of learned knowledge to much larger problem instances containing many objects.

IJCAI Conference 2022 Conference Paper

Relational Abstractions for Generalized Reinforcement Learning on Symbolic Problems

  • Rushang Karia
  • Siddharth Srivastava

Reinforcement learning in problems with symbolic state spaces is challenging due to the need for reasoning over long horizons. This paper presents a new approach that utilizes relational abstractions in conjunction with deep learning to learn a generalizable Q-function for such problems. The learned Q-function can be efficiently transferred to related problems that have different object names and object quantities, and thus, entirely different state spaces. We show that the learned, generalized Q-function can be utilized for zero-shot transfer to related problems without an explicit, hand-coded curriculum. Empirical evaluations on a range of problems show that our method facilitates efficient zero-shot transfer of learned knowledge to much larger problem instances containing many objects.

AAMAS Conference 2022 Conference Paper

Using Deep Learning to Bootstrap Abstractions for Hierarchical Robot Planning

  • Naman Shah
  • Siddharth Srivastava

This paper addresses the problem of learning abstractions that boost robot planning performance while providing strong guarantees of reliability. Although state-of-the-art hierarchical robot planning algorithms allow robots to efficiently compute long-horizon motion plans for achieving user desired tasks, these methods typically rely upon environment-dependent state and action abstractions that need to be hand-designed by experts. We present a new approach for bootstrapping the entire hierarchical planning process. This allows us to compute abstract states and actions for new environments automatically using the critical regions predicted by a deep neural network with an auto-generated robot-specific architecture. We show that the learned abstractions can be used with a novel multi-source bi-directional hierarchical robot planning algorithm that is sound and probabilistically complete. An extensive empirical evaluation on twenty different settings using holonomic and non-holonomic robots shows that (a) our learned abstractions provide the information necessary for efficient multi-source hierarchical planning; and that (b) this approach of learning, abstractions, and planning outperforms state-of-the-art baselines by nearly a factor of ten in terms of planning time on test environments not seen during training.

AAAI Conference 2021 Conference Paper

Asking the Right Questions: Learning Interpretable Action Models Through Query Answering

  • Pulkit Verma
  • Shashank Rao Marpally
  • Siddharth Srivastava

This paper develops a new approach for estimating an interpretable, relational model of a black-box autonomous agent that can plan and act. Our main contributions are a new paradigm for estimating such models using a rudimentary query interface with the agent and a hierarchical querying algorithm that generates an interrogation policy for estimating the agent’s internal model in a user-interpretable vocabulary. Empirical evaluation of our approach shows that despite the intractable search space of possible agent models, our approach allows correct and scalable estimation of interpretable agent models for a wide class of black-box autonomous agents. Our results also show that this approach can use predicate classifiers to learn interpretable models of planning agents that represent states as images.

AAAI Conference 2021 Conference Paper

Learning Generalized Relational Heuristic Networks for Model-Agnostic Planning

  • Rushang Karia
  • Siddharth Srivastava

Computing goal-directed behavior is essential to designing efficient AI systems. Due to the computational complexity of planning, current approaches rely primarily upon hand-coded symbolic action models and hand-coded heuristic function generators for efficiency. Learned heuristics for such problems have been of limited utility as they are difficult to apply to problems with objects and object quantities that are significantly different from those in the training data. This paper develops a new approach for learning generalized heuristics in the absence of symbolic action models using deep neural networks that utilize an input predicate vocabulary but are agnostic to object names and quantities. It uses an abstract state representation to facilitate data-efficient, generalizable learning. Empirical evaluation on a range of benchmark domains shows that in contrast to prior approaches, generalized heuristics computed by this method can be transferred easily to problems with different objects and with object quantities much larger than those in the training data.

AAAI Conference 2021 Conference Paper

Unifying Principles and Metrics for Safe and Assistive AI

  • Siddharth Srivastava

The prevalence and success of AI applications have been tempered by concerns about the controllability of AI systems about AI’s impact on the future of work. These concerns reflect two aspects of a central question: how would humans work with AI systems? While research on AI safety focuses on designing AI systems that allow humans to safely instruct and control AI systems, research on AI and the future of work focuses on the impact of AI on humans who may be unable to do so. This Blue Sky Ideas paper proposes a unifying set of declarative principles that enable a more uniform evaluation of arbitrary AI systems along multiple dimensions of the extent to which they are suitable for use by specific classes of human operators. It leverages recent AI research and the unique strengths of the field to develop human-centric principles for AI systems that address the concerns noted above.

AIJ Journal 2021 Journal Article

Using state abstractions to compute personalized contrastive explanations for AI agent behavior

  • Sarath Sreedharan
  • Siddharth Srivastava
  • Subbarao Kambhampati

There is a growing interest within the AI research community in developing autonomous systems capable of explaining their behavior to users. However, the problem of computing explanations for users of different levels of expertise has received little research attention. We propose an approach for addressing this problem by representing the user's understanding of the task as an abstraction of the domain model that the planner uses. We present algorithms for generating minimal explanations in cases where this abstract human model is not known. We reduce the problem of generating an explanation to a search over the space of abstract models and show that while the complete problem is NP-hard, a greedy algorithm can provide good approximations of the optimal solution. We empirically show that our approach can efficiently compute explanations for a variety of problems and also perform user studies to test the utility of state abstractions in explanations.

AAAI Conference 2019 Conference Paper

A Unified Framework for Planning in Adversarial and Cooperative Environments

  • Anagha Kulkarni
  • Siddharth Srivastava
  • Subbarao Kambhampati

Users of AI systems may rely upon them to produce plans for achieving desired objectives. Such AI systems should be able to compute obfuscated plans whose execution in adversarial situations protects privacy, as well as legible plans which are easy for team members to understand in cooperative situations. We develop a unified framework that addresses these dual problems by computing plans with a desired level of comprehensibility from the point of view of a partially informed observer. For adversarial settings, our approach produces obfuscated plans with observations that are consistent with at least k goals from a set of decoy goals. By slightly varying our framework, we present an approach for producing legible plans in cooperative settings such that the observation sequence projected by the plan is consistent with at most j goals from a set of confounding goals. In addition, we show how the observability of the observer can be controlled to either obfuscate or convey the actions in a plan when the goal is known to the observer. We present theoretical results on the complexity analysis of our approach. We also present an empirical evaluation to show the feasibility and usefulness of our approaches using IPC domains.

IJCAI Conference 2019 Conference Paper

Why Can’t You Do That HAL? Explaining Unsolvability of Planning Tasks

  • Sarath Sreedharan
  • Siddharth Srivastava
  • David Smith
  • Subbarao Kambhampati

Explainable planning is widely accepted as a prerequisite for autonomous agents to successfully work with humans. While there has been a lot of research on generating explanations of solutions to planning problems, explaining the absence of solutions remains an open and under-studied problem, even though such situations can be the hardest to understand or debug. In this paper, we show that hierarchical abstractions can be used to efficiently generate reasons for unsolvability of planning problems. In contrast to related work on computing certificates of unsolvability, we show that these methods can generate compact, human-understandable reasons for unsolvability. Empirical analysis and user studies show the validity of our methods as well as their computational efficacy on a number of benchmark planning domains.

IJCAI Conference 2018 Conference Paper

Hierarchical Expertise Level Modeling for User Specific Contrastive Explanations

  • Sarath Sreedharan
  • Siddharth Srivastava
  • Subbarao Kambhampati

There is a growing interest within the AI research community in developing autonomous systems capable of explaining their behavior to users. However, the problem of computing explanations for users of different levels of expertise has received little research attention. We propose an approach for addressing this problem by representing the user's understanding of the task as an abstraction of the domain model that the planner uses. We present algorithms for generating minimal explanations in cases where this abstract human model is not known. We reduce the problem of generating an explanation to a search over the space of abstract models and show that while the complete problem is NP-hard, a greedy algorithm can provide good approximations of the optimal solution. We also empirically show that our approach can efficiently compute explanations for a variety of problems.

IJCAI Conference 2016 Conference Paper

Markovian State and Action Abstractions for MDPs via Hierarchical MCTS

  • Aijun Bai
  • Siddharth Srivastava
  • Stuart Russell

State abstraction is an important technique for scaling MD Palgorithms. As is well known, however, it introduces difficulties due to the non-Markovian nature of state-abstracted models. Whereas prior approaches rely upon ad hoc fixes for this issue, we propose instead to view the state-abstracted model as a POMDP and show that we can thereby take advantage of state abstraction without sacrificing the Markov property. We further exploit the hierarchical structure introduced by state abstraction by extending the theory of options to a POMDP setting. In this context we propose a hierarchical Monte Carlo tree search algorithm and show that it converges to a recursively optimal hierarchical policy. Both theoretical and empirical results suggest that abstracting an MDP into a POMDP yields a scalable solution approach.

AAAI Conference 2016 Conference Paper

Metaphysics of Planning Domain Descriptions

  • Siddharth Srivastava
  • Stuart Russell
  • Alessandro Pinto

STRIPS-like languages (SLLs) have fostered immense advances in automated planning. In practice, SLLs are used to express highly abstract versions of real-world planning problems, leading to more concise models and faster solution times. Unfortunately, as we show in the paper, simple ways of abstracting solvable real-world problems may lead to SLL models that are unsolvable, SLL models whose solutions are incorrect with respect to the real-world problem, or models that are inexpressible in SLLs. There is some evidence that such limitations have restricted the applicability of AI planning technology in the real world, as is apparent in the case of task and motion planning in robotics. We show that the situation can be ameliorated by a combination of increased expressive power—for example, allowing angelic nondeterminism in action effects—and new kinds of algorithmic approaches designed to produce correct solutions from initially incorrect or non-Markovian abstract models.

AAAI Conference 2015 Conference Paper

Tractability of Planning with Loops

  • Siddharth Srivastava
  • Shlomo Zilberstein
  • Abhishek Gupta
  • Pieter Abbeel
  • Stuart Russell

We create a unified framework for analyzing and synthesizing plans with loops for solving problems with nondeterministic numeric effects and a limited form of partial observability. Three different action models—with deterministic, qualitative non-deterministic and Boolean nondeterministic semantics—are handled using a single abstract representation. We establish the conditions under which the correctness and termination of solutions, represented as abstract policies, can be verified. We also examine the feasibility of learning abstract policies from examples. We demonstrate our techniques on several planning problems and show that they apply to challenging real-world tasks such as doing the laundry with a PR2 robot. These results resolve a number of open questions about planning with loops and facilitate the development of new algorithms and applications.

AIJ Journal 2012 Journal Article

Applicability conditions for plans with loops: Computability results and algorithms

  • Siddharth Srivastava
  • Neil Immerman
  • Shlomo Zilberstein

The utility of including loops in plans has been long recognized by the planning community. Loops in a plan help increase both its applicability and the compactness of its representation. However, progress in finding such plans has been limited largely due to lack of methods for reasoning about the correctness and safety properties of loops of actions. We present novel algorithms for determining the applicability and progress made by a general class of loops of actions. These methods can be used for directing the search for plans with loops towards greater applicability while guaranteeing termination, as well as in post-processing of computed plans to precisely characterize their applicability. Experimental results demonstrate the efficiency of these algorithms. We also discuss the factors which can make the problem of determining applicability conditions for plans with loops incomputable.

AIJ Journal 2011 Journal Article

A new representation and associated algorithms for generalized planning

  • Siddharth Srivastava
  • Neil Immerman
  • Shlomo Zilberstein

Constructing plans that can handle multiple problem instances is a longstanding open problem in AI. We present a framework for generalized planning that captures the notion of algorithm-like plans and unifies various approaches developed for addressing this problem. Using this framework, and building on the TVLA system for static analysis of programs, we develop a novel approach for computing generalizations of classical plans by identifying sequences of actions that will make measurable progress when placed in a loop. In a wide class of problems that we characterize formally in the paper, these methods allow us to find generalized plans with loops for solving problem instances of unbounded sizes and also to determine the correctness and applicability of the computed generalized plans. We demonstrate the scope and scalability of the proposed approach on a wide range of planning problems.

AAAI Conference 2011 Conference Paper

Qualitative Numeric Planning

  • Siddharth Srivastava
  • Shlomo Zilberstein
  • Neil Immerman
  • Hector Geffner

We consider a new class of planning problems involving a set of non-negative real variables, and a set of non-deterministic actions that increase or decrease the values of these variables by some arbitrary amount. The formulas specifying the initial state, goal state, or action preconditions can only assert whether certain variables are equal to zero or not. Assuming that the state of the variables is fully observable, we obtain two results. First, the solution to the problem can be expressed as a policy mapping qualitative states into actions, where a qualitative state includes a Boolean variable for each original variable, indicating whether its value is zero or not. Second, testing whether any such policy, that may express nested loops of actions, is a solution to the problem, can be determined in time that is polynomial in the qualitative state space, which is much smaller than the original infinite state space. We also report experimental results using a simple generateand-test planner to illustrate these findings.

AAAI Conference 2011 Conference Paper

Termination and Correctness Analysis of Cyclic Control

  • Siddharth Srivastava
  • Neil Immerman
  • Shlomo Zilberstein

The utility of including cyclic flow of control in plans has been long recognized by the planning community. Loops in a plan increase both its applicability and the compactness of representation. However, progress in finding such plans has been limited largely due to lack of methods for reasoning about the correctness and applicability of loops of actions. We present an overview of recent results for determining the class of problems that a plan with loops can solve. These methods can be used to direct the construction of a rich new form of generalized plans that solve a desired class of problems.

AAMAS Conference 2010 Conference Paper

Merging Example Plans into Generalized Plans for Non-deterministic Environments

  • Siddharth Srivastava
  • Neil Immerman
  • Shlomo Zilberstein

We present a new approach for finding contingent plans with loops andbranches in situations where there is uncertainty instate properties and object quantities, but lack of probabilisticinformation about these uncertainties. We use a state abstractiontechnique from static analysis of programs which uses 3-valued logicto compactly represent belief states with unbounded numbers ofobjects. Our approach for finding plans is to incrementallygeneralize and merge input example plans which can be generated byclassical planners. The expressiveness and scope of this approach aredemonstrated using experimental results on common benchmark domains.

AAAI Conference 2008 Conference Paper

Learning Generalized Plans Using Abstract Counting

  • Siddharth Srivastava

Given the complexity of planning, it is often beneficial to create plans that work for a wide class of problems. This facilitates reuse of existing plans for different instances drawn from the same problem or from an infinite family of similar problems. We define a class of such planning problems called generalized planning problems and present a novel approach for transforming classical plans into generalized plans. These algorithm-like plans include loops and work for problem instances having varying numbers of objects that must be manipulated to reach the goal. Our approach takes as input a classical plan for a certain problem instance. It outputs a generalized plan along with a classification of the problem instances where it is guaranteed to work. We illustrate the utility of our approach through results of a working implementation on various practical examples.

YNIMG Journal 2005 Journal Article

Feature-based statistical analysis of structural MR data for automatic detection of focal cortical dysplastic lesions

  • Siddharth Srivastava
  • Frederik Maes
  • Dirk Vandermeulen
  • Wim Van Paesschen
  • Patrick Dupont
  • Paul Suetens

This paper presents a method for fully automated detection and localization of Focal Cortical Dysplastic (FCD) lesions from anatomical magnetic resonance (MR) images of the human brain. Model-based tissue classification of the image under study was applied first such that a gray matter (GM) segmentation map is obtained of which we demonstrate that it also includes possible FCD lesions. Cortical thickness was estimated at each voxel using an appropriate distance transform applied to the binarized GM object and an FCD specific feature map was constructed by computing the ratio of cortical thickness over absolute image intensity gradient at each voxel. In absence of any prior anatomical hypothesis on the spatial location of the lesion, a statistical parameter map was constructed by evaluating the evidence for each gray matter voxel against the null hypothesis of no difference in the feature map of the patient versus similar maps obtained for a group of normal controls. Voxel clusters for which the null hypothesis was found to be improbable at optimally selected thresholds for cluster height and extent were reported as lesions. The method was applied to a surgical series of 17 FCD patient images that were compared against a group of 64 neurologically normal controls. The method correctly detected and located the FCD lesion in 9 out of 17 FCD cases (53%) using a threshold that minimized false positives and 12 of 17 (71%) using a threshold that allowed more false positive results. The detected lesions had a median volume of 7. 2 cm3 versus 2. 9 cm3 for the non-detected lesions. The detected lesions more often had an increased cortical thickness on T1 than the non-detected lesions (P = 0. 015, Fisher's exact test). Due to a high variance of the feature maps in the temporal lobes and insula, detection of FCD lesions in these regions appeared more difficult than in other brain regions with lower variance.

v2026.09.13