Roman Barták

Roman Barták
Charles University in Prague | CUNI · Department of Theoretical Computer Science and Mathematical Logic

Prof.

About

270
Publications
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Introduction
I am working in the area of model-based artificial intelligence, specifically planning, scheduling, constraint satisfaction, and knowledge representation with some flavor of machine learning and robotics. We solve problems by first formally modeling them and then using a compilation-based approach to solve them (for example, compilation to CSP or SAT). Recently, I work on modeling planning problems and automated acquisition of domain models, on hierarchical planning (plan verification and plan recognition) and on multi-agent path finding with applications on real robots (warehouses, road junctions).

Publications

Publications (270)
Article
Verification of hierarchical plans deals with the problem if a given action sequence is a valid hierarchical plan – the action sequence can be obtained by decomposing a particular (goal) task using given decomposition methods. The existing parsing-based verification approach greedily composes actions until it obtains the goal task. Greediness impli...
Conference Paper
Hierarchical task network (HTN) planning is a model-based approach to planning. The HTN domain model consists of tasks and methods to decompose them into subtasks until obtaining primitive tasks (actions). There are recent methods for verifying if a given action sequence is a valid HTN plan. However, if the plan is invalid, all existing verificatio...
Article
Multi-agent Path Finding (MAPF) deals with finding collision-free paths for a set of agents on a graph, where each agent has its origin and destination. Colored MAPF is a generalization of MAPF, where groups of agents are moving, and the set of destination nodes is specified per group rather than per agent. OzoMorph is software providing an intuiti...
Article
Full-text available
Multi-Agent Path Finding (MAPF) deals with the problem of finding collision-free paths for a set of agents moving in a shared environment while each agent has specified its destination. Colored MAPF generalizes MAPF by defining groups of agents that share a set of destination locations. In the paper, we evaluate several approaches to optimally solv...
Chapter
Automated planning deals with the problem of finding a sequence of actions leading from a given state to a desired state. The state-of-the-art automated planning techniques exploit informed forward search guided by a heuristic which is used to estimate a distance from a state to a goal state. In this paper, we present a technique to automatically c...
Article
Domain-independent planning decouples planning task specification and planning engines. As the specification is usually describing only the physics of the environment, actions and a goal, the planning engines being generic solvers designed to solve any planning task tend to struggle with tasks that can be easily solved by domain-specific algorithms...
Article
Multi-Agent Path Finding (MAPF) deals with finding collision free paths for a set of agents (robots) moving on a graph. The interest in MAPF in the research community started to increase recently partly due to practical applications in areas such as warehousing and computer games. However, the academic community focuses mostly on solving the abstra...
Chapter
Planning and scheduling are two closely related areas that deal with organizing activities to achieve a particular goal (planning) and allocating these activities to limited time and resources for execution (scheduling). However, regarding the tools supporting the planning and scheduling processes, these two areas are still far from each other. Pro...
Article
Full-text available
Multi-agent path-finding (MAPF) is the problem of finding a plan for moving a set of agents from their initial locations to their goals without collisions. Following this plan, however, may not be possible due to unexpected events that delay some of the agents. In this work, we propose a holistic solution for MAPF that is robust to such unexpected...
Article
The Thirty-Second International Florida Artificial Intelligence Research Society Conference was held May 19–22, 2019, at the Lido Beach Resort in Sarasota, Florida, USA. The conference events included tutorials, invited speakers, special tracks, and presentations of papers, posters, and awards. The conference chair was Vasile Rus from the Universit...
Conference Paper
Full-text available
Multi-agent path finding (MAPF) is the problem to find collision-free paths for a set of agents (mobile robots) moving on a graph. There exists several abstract models describing the problem with various types of constraints. The demo presents software to evaluate the abstract models when the plans are executed on Ozobots, small mobile robots devel...
Article
Multi-agent pathfinding (MAPF) is the problem of moving a group of agents to a set of target destinations while avoiding collisions. In this work, we study the online version of MAPF where new agents appear over time. Several variants of online MAPF are defined and analyzed theoretically, showing that it is not possible to create an optimal online...
Preprint
Full-text available
The MAPF problem is the fundamental problem of planning paths for multiple agents, where the key constraint is that the agents will be able to follow these paths concurrently without colliding with each other. Applications of MAPF include automated warehouses and autonomous vehicles. Research on MAPF has been flourishing in the past couple of years...
Article
The Thirty-First International Florida Artificial Intelligence Research Society Conference (FLAIRS-31) was held May 21-23, 2018, at the Crowne Plaza Oceanfront in Melbourne, Florida, USA. The conference events included invited speakers, special tracks, and presentations of papers, posters, and awards. The conference chair was Zdravko Markov from Ce...
Chapter
The problem of Multi-Agent Path Finding (MAPF) is to find paths for a fixed set of agents from their current locations to some desired locations in such a way that the agents do not collide with each other. This problem has been extensively theoretically studied, frequently using an abstract model, that expects uniform durations of moving primitive...
Chapter
Planning domain models are critical input to current automated planners. These models provide description of planning operators that formalize how an agent can change the state of the world. It is not easy to obtain accurate description of planning operators, namely to ensure that all preconditions and effects are properly specified. Therefore auto...
Conference Paper
Full-text available
In the multi-agent path-finding (MAPF) problem, the task is to find a plan for moving a set of agents from their initial locations to their goals without collisions. Following this plan, however, may not be possible due to unexpected events that delay some of the agents. We explore the notion of k-robust MAPF, where the task is to find a plan that...
Article
An important problem of automated planning is validating if a plan complies with the domain model. Such validation is straightforward for classical sequential planning but until recently there was no plan validation approach for Hierarchical Task Networks (HTN). In this paper we propose a novel technique for validating HTN plans by parsing of attri...
Chapter
We propose a novel 3D navigation system for autonomous vehicle path-planning. The system processes a point-cloud data from an RGB-D camera and creates a 3D occupancy grid with adaptable cell size. Occupied grid cells contain normal distribution characterizing the data measured in the area of the cell. The normal distributions are then used for cell...
Book
Full-text available
Roboti, drony a různý software se z laboratoří přesouvají do běžného života. Již dnes řeší automatizované systémy řadu úkolů lépe než lidé, ale také dělají z lidského hlediska nepředstavitelné chyby. Sebere nám umělá inteligence práci? Nebo se naopak máme těšit, že budeme mít více času na jiné aktivity? Máme se obávat vzniku super-inteligence, kter...
Conference Paper
The multi-agent pathfinding (MAPF) problem has attracted considerable attention because of its relation to practical applications. In this paper, we present a constraint-based declarative model for MAPF, together with its implementation in Picat, a logic-based programming language. We show experimentally that our Picat-based implementation is highl...
Conference Paper
The paper presents attribute grammars as a unifying framework for modeling planning domains and problems. The motivation is to exploit techniques from formal languages in domain model verification, plan and goal recognition, domain model acquisition, as well as in planning. Grammar rules are used for action selection while specific set attributes a...
Article
Full-text available
The AAAI-17 workshop program included 17 workshops covering a wide range of topics in AI. Workshops were held Sunday and Monday, February 4-5, 2017 at the Hilton San Francisco Union Square in San Francisco, California, USA. This report contains summaries of 12 of the workshops, and brief abstracts of the remaining 5.
Conference Paper
Recently, attribute grammars have been suggested as a unifying framework to describe workflow and planning domains models. One of the critical aspects of the domain model is its soundness, that is, the model should not contain any dead-ends and should describe at least one plan. In this paper we describe how the domain model can be verified by usin...
Conference Paper
Full-text available
Attaining optimal results in real-life scheduling is hindered by a number of problems. One such problem is dynamics of manufacturing environments with breaking-down resources and hot orders coming during the schedule execution. A traditional approach to react to unexpected events occurring on the shop floor is generating a new schedule from scratch...
Conference Paper
Grammar checking has been used for a long time to validate if a given sentence - a sequence of words - complies with grammar rules. Recently attribute grammars have been proposed as a formal model to describe workflows. A workflow specifies valid processes, which are sequences of actions. In this paper we show how a grammar checker developed for na...
Article
Action planning deals with the problem of finding a sequence of actions transferring the world from a given state to a desired (goal) state. This problem is important in various areas such as robotics, manufacturing, transportation, autonomic computing, computer games, etc. Action planning is a form of a reachability problem in a huge state space s...
Article
The areas of Artificial Intelligence planning and scheduling have seen important advances thanks to the application of constraint satisfaction models and techniques. Especially, solutions to many real-world problems need to integrate plan synthesis capabilities with resource allocation, which can be efficiently managed by using constraint satisfact...
Article
Constraint Solving and Planning with Picat by Neng-Fa Zhou , Håkan Kjellerstrand , and Jonathan Fruhman , xi + 148 pages, Springer, 2015. Paperback, ISBN 978-3-319-25881-2. - Volume 17 Issue 1 - ROMAN BARTÁK
Conference Paper
Solar arrays are the main source of energy at the International Space Station (ISS). Most of the time they automatically track the sun, but some ISS operations impose additional constraints on the arrays and the arrays may need to be parked or even locked. These operations must be carefully planned to prevent thermal stresses, environmental contami...
Conference Paper
Workflow is a formal description of a process. Nested workflows were proposed to model processes with a hierarchical structure and they support extra logical and temporal constraints to express relations beyond the hierarchical structure. This workflow model supports scheduling applications with a known number of activities in the process, but it c...
Article
Attaining optimal results in real-life scheduling is hindered by a number of problems. One such problem is dynamics of manufacturing environments with breaking-down resources and hot orders coming during the schedule execution. A traditional approach to react to unexpected events occurring on the shop floor is generating a new schedule from scratch...
Article
Full-text available
Solving planning problems via translation to satisfiability (SAT) is one of the most successful approaches to automated planning. We propose a new encoding scheme, called Reinforced Encoding, which encodes a planning problem represented in the SAS+ formalism into SAT. The Reinforced Encoding is a combination of the transition-based SASE encoding wi...
Article
Full-text available
We present a project that aggregates various existing robotic software and serves as a platform to conveniently control a quadrocopter, mainly for research or educational purposes. User interface runs in a browser and other components are also made with portability in mind. We provide a common interface that unifies different quadrocopter models an...
Article
Many contemporary computer games, notably action and role-playing games, represent an interesting class of navigation-intensive dynamic real-time simulations inhabited by autonomous intelligent virtual agents (IVAs). Although higher level reasoning of IVAs in these domains seems suited for action planning, planning is not widely adopted in existing...
Conference Paper
Nomystery is a simple logistic planning domain proposed for the International Planning Competition. The task is to plan loading, driving, and unloading actions for a single truck with unlimited load capacity but with limited fuel to transport packages between various locations. In this paper we show how different modeling techniques influence effic...
Conference Paper
Current consumer electronics is equipped with various sensors, among which accelerometer, gyroscope, and magnetometer represent typical examples. In this paper, we study the possibility of using these low-cost sensors for 3D motion and orientation tracking. In particular, we thoroughly describe a simple dead-reckoning algorithm for sensor data fusi...
Article
Full-text available
This paper describes Picat's planner, its implementation, and planning models for several domains used in International Planning Competition (IPC) 2014. Picat's planner is implemented by use of tabling. During search, every state encountered is tabled, and tabled states are used to effectively perform resource-bounded search. In Picat, structured d...
Conference Paper
Current research in planning focuses mainly on so called domain independent models using the Planning Domain Description Language (PDDL) as the domain modeling language. This declarative modeling approach embraces the idea of a physics-only model describing how actions change the world. However, PDDL omits information about why and when the actions...
Article
AI Planning is inherently hard and hence it is desirable to derive as much information as we can from the structure of the planning problem and let this information be exploited by a planner. Many recent planners use the finite-domain state-variable representation of the problem instead of the classical propositional representation. However, most p...
Conference Paper
Full-text available
One of the problems of real-life production scheduling is dynamics of manufacturing environments with new production demands coming and breaking machines during the schedule execution. Simple rescheduling from scratch in response to unexpected events may require excessive computation time. Moreover, the recovered schedule may deviate prohibitively...
Article
One of the classical problems of real-life production scheduling is dynamics of manufacturing environments with new production demands coming and breaking machines during the schedule execution. Simple rescheduling from scratch in response to unexpected events occurring on the shop floor may require excessive computation time. Moreover, the recover...
Conference Paper
The Mars Express mission is a space exploration mission being conducted by the European Space Agency. The Mars Express Orbiter is extremely successful and is performing scientific experiments since early 2004, generating 2-3Gbit of scientific data per day. It is therefore very important to plan its activities properly to obtain high-quality scienti...
Conference Paper
Knowledge engineering for automated planning is still in its childhood and there has been little work done on how to model planning problems. The prevailing approach in the academic community is using the PDDL language that originated in planning competitions. In contrast, real applications require more modeling flexibility and different modeling l...
Article
Full-text available
Tabling has been used for some time to improve efficiency of Prolog programs by memorizing answered queries. The same idea can be naturally used to memorize visited states during search for planning. In this paper we present a planner developed in the Picat language to solve the Petrobras planning problem. Picat is a novel Prolog-like language that...
Conference Paper
Full-text available
In recent years, many so called “robotic toys” appeared at the market. Though these devices are called toys and they are primarily intended for games, they provide a set of sensors and actuators that can be controlled from a computer. Hence these robotic devices may serve as non-expensive research tools, in particular for developing advanced softwa...
Article
Solving challenging computational problems involving time has been a critical component in the development of artificial intelligence systems almost since the inception of the field. .is book provides a concise introduction to the core computational elements of temporal reasoning for use in AI systems for planning and scheduling, as well as systems...
Article
Workflows are used to formally describe processes of various types such as business and manufacturing processes. One of the critical tasks of workflow management is automated discovery of possible flaws in the workflow - workflow verification. In this paper, we formalize the problem of workflow verification as the problem of verifying that there ex...
Article
Full-text available
Autonomous landing is one of the must-have operations of unmanned aerial vehicles such as drones. In this paper we describe an approach for fully autonomous landing of AR.Drones. This approach consists of two components - identifying and recognizing a proper pattern used to mark the landing area and reaching the landing area (landing) even if small...
Article
With more computing power available, video games may spare increasing amounts of processing time for AI. One prospective application of the newly available resources is the simulation of large amounts of nonplayer characters (NPCs) in open world games. While it is relatively easy to simulate simple behaviours of individual NPCs it is much more diff...
Chapter
Physics teaches us that time is fundamental to the understanding of the material world. Continuous physical processes like waves, flows, and oscillations are characterized in terms of changes, and rates of change, of the world over time.
Chapter
The representation of temporal information, and reasoning about time, are important in artificial intelligence. Reasoning about time plays an important role in building automated planning and scheduling systems, where causal and temporal relations are the most critical concepts. Time also enters into areas such as natural language processing, for e...
Chapter
We will now consider how the formalisms described in the previous chapter can be extended. Although remarkably expressive, none of the approaches we have seen so far allow to distinguish among solutions according to preferences we may have on how constraints should be satisfied. Moreover, all the variables are assumed to be under the control of the...
Conference Paper
The International Planning Competitions have led to development of a standard modeling framework for describing planning domains and problems – Planning Domain Description Language (PDDL). The majority of planning research is done around problems modeled in PDDL though there are only a few applications adopting PDDL. The planning model of independe...
Conference Paper
Monte Carlo Tree Search (MCTS) techniques brought fresh breeze to the area of computer games where they significantly improved solving algorithms for games such as Go. MCTS also worked well when solving a real-life planning problem of the Petrobras company brought by the Fourth International Competition on Knowledge Engineering Techniques for Plann...
Article
Inductive Logic Programming (ILP) deals with the problem of finding a hypothesis covering positive examples and excluding negative examples, where both hypotheses and examples are expressed in first-order logic. In this paper we employ constraint satisfaction techniques to model and solve a problem known as template ILP consistency, which assumes t...
Article
Workflow verification is an important aspect of workflow modeling where the verification task is to ensure that the workflow describes feasible processes. It has been shown that verifying nested workflows with extra precedence, causal, and temporal synchronization constraints is an NP-complete problem and a verification method based on constraint s...
Article
Many contemporary computer games can be described as dynamic real-time simulations inhabited by autonomous intelligent virtual agents (IVAs) where most of the environmental structure is immutable and navigating through the environment is one of the most common activities. Though controlling the behaviour of such agents seems perfectly suited for ac...
Conference Paper
The Petrobras domain is an abstraction of a real-life problem of resource-efficient transportation of goods from ports to petroleum platforms. Being a good example of a difficult problem standing on the borderline between planning and scheduling, this domain was proposed as a challenge problem at the International Competition on Knowledge Engineeri...
Conference Paper
Full-text available
There exist planning algorithms that can quickly find sub-optimal plans even for large problems and planning algorithms finding optimal plans but only for smaller problems. In this paper we attempt to integrate both approaches. We present an anytime technique for improving plan quality, in particular for decreasing the plan make span, via substitut...
Conference Paper
Nested workflows are used to formally describe processes with a hierarchical structure similar to hierarchical task networks in planning. The nested structure guarantees that the workflow is sound in terms of possibility to select for each involved activity a process that contains the activity. However, if extra synchronization, precedence, or caus...
Conference Paper
Inductive Logic Programming (ILP) deals with the problem of finding a hypothesis covering positive examples and excluding negative examples. It uses first-order logic as a uniform representation for examples and hypothesis. In this paper we propose a method to boost any ILP learning algorithm by first decomposing the set of examples to subsets and...
Article
Full-text available
The massive data processing in a multi-collaboration environment with geographically spread diverse facilities will be hardly "fair" to users and hardly using network bandwidth efficiently unless we address and deal with planning and reasoning related to data movement and placement. The needs for coordinated data resource sharing and efficient plan...
Conference Paper
The paper presents a performance prediction and optimisation tool MAK€that allows users to model enterprises in a visually rich and intuitive way. The tool automatically generates a scheduling model describing all choices that users can do when optimising production. This model then goes to the Optimiser Module that generates schedules optimising o...
Article
Inductive logic programming is a machine learning method that combines inductive learning with the representation of hypotheses as logic programs. There exist methods that given a template find unification of variables in the template to obtain a hypothesis that subsumes all positive examples and does not subsume any negative example. In this paper...
Article
Workflow is a formal description of a process or processes. There exist tools for interactive and visual editing of workflows such as the FlowOpt Workflow Editor. During manual editing of workflows, it is common to introduce flaws such as cycles of activities. Hence one of the required features of workflow management tools is verification of workfl...
Article
This paper deals with planning domains that appear in computer games, especially when modeling intelligent virtual agents. Some of these domains contain only actions with no negative effects and are thus treated as easy from the planning perspective. We propose two new techniques to solve the problems in these planning domains, a heuristic search a...