Engineering a Conformant Probabilistic Planner

We present a partial-order, conformant, probabilistic planner, Probapop which competed in the blind track of the Probabilistic Planning Competition in IPC-4. We explain how we adapt distance based heuristics for use with probabilistic domains. Probapop also incorporates heuristics based on probability of success. We explain the successes and difficulties encountered during the design and implementation of Probapop

Planning and learning under uncertainty

Automated Planning is the component of Artificial Intelligence that studies the computational process of synthesizing sets of actions whose execution achieves some given objectives. Research on Automated Planning has traditionally focused on solving theoretical problems in controlled environments. In such environments both, the current state of the environment and the outcome of actions, are completely known. The development of real planning applications during the last decade (planning fire extinction operations (Castillo et al., 2006), planning spacecraft activities (Nayak et al., 1999), planning emergency evacuation actions (Muñoz-Avila et al., 1999) has evidenced that these two assumptions are not true in many real-world problems. The planning research community is aware of this issue and during the last years, it has multiply its efforts to find new planning systems able to address these kinds of problems. All these efforts have created a new field in Automated Planning called planning under uncertainty. Nevertheless, the new systems suffer from two limitations. (1) They precise accurate action models, though the definition by hand of accurate action models is frequently very complex. (2) They present scalability problems due to the combinatorial explosion implied by the expressiveness of its action models. This thesis defines a new planning paradigm for building, in an efficient and scalable way, robust plans in domains with uncertainty though the action model is incomplete. The thesis is that, the integration of relational machine learning techniques with the planning and execution processes, allows to develop planning systems that automatically enrich their initial knowledge about the environment and therefore find more robust plans. An empirical evaluation illustrates these benefits in comparison with state-of-the-art probabilistic planners which use static actions models. -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------La Planificación Automática es la rama de la Inteligencia Artificial que estudia los procesos computacionales para la síntesis de conjuntos de acciones cuya ejecución permita alcanzar unos objetivos dados. Históricamente, la investigación en esta rama ha tratado de resolver problemas teóricos en entornos controlados en los que conocía tanto el estado actual del entorno como el resultado de ejecutar acciones en él. En la última década, el desarrollo de aplicaciones de planificación (gestión de las tareas de extinción de incendios forestales (Castillo et al., 2006), control de las actividades de la nave espacial Deep Space 1 (Nayak et al., 1999), planificación de evacuaciones de emergencia (Muñoz-Avila et al., 1999) ha evidenciado que tales supuestos no son ciertos en muchos problemas reales. Consciente de ello, la comunidad investigadora ha multiplicado sus esfuerzos para encontrar nuevos paradigmas de planificación que se ajusten mejor a este tipo de problemas. Estos esfuerzos han llevado al nacimiento de una nueva área dentro de la Planificación Automática, llamada planificación con incertidumbre. Sin embargo, los nuevos planificadores para dominios con incertidumbre aún presentan dos importantes limitaciones: (1) Necesitan modelos de acciones detallados que contemplen los posibles resultados de ejecutar cada acción. En la mayoría de problemas reales es difícil obtener modelos de este tipo. (2) Presentan fuertes problemas de escalabilidad debido a la explosión combinatoria que provoca la complejidad de los modelos de acciones que manejan. En esta Tesis se define un paradigma de planificación capaz de generar, de forma eficiente y escalable, planes robustos en dominios con incertidumbre aunque no se disponga de modelos de acciones completamente detallados. La Tesis que se defiende es que la integración de técnicas de aprendizaje automático relacional con los procesos de decisión y ejecución permite desarrollar sistemas de planificación capaces de enriquecer automáticamente su modelo de acciones con información adicional que les ayuda a encontrar planes más robustos. Los beneficios de esta integración son evaluados experimentalmente mediante una comparación con planificadores probabilísticos del estado del arte los cuales no modifican su modelo de acciones

Smoke Test Planning using Answer Set Programming

Smoke testing is an important method to increase stability and reliability of hardware- gramming, Testing depending systems. Due to concurrent access to the same physical resource and the impracticality of the use of virtualization, smoke testing requires some form of planning. In this paper, we propose to decompose test cases in terms of atomic actions consisting of preconditions and effects. We present a solution based on answer set programming with multi-shot solving that automatically generates short parallel test plans. Experiments suggest that the approach is feasible for non-inherently sequential test cases and scales up to thousands of test cases

Monitoring plan execution in partially observable stochastic worlds

This thesis presents two novel algorithms for monitoring plan execution in stochastic partially observable environments. The problems can be formulated as partially-observable Markov decision processes (POMDPs). Exact solutions of POMDP problems are difficult to find due to the computational complexity, so many approximate solutions are proposed instead. These POMDP solvers tend to generate an approximate policy at planning time and execute the policy without any change at run time. Our approaches will monitor the execution of the initial approximate policy and perform plan modification procedure to improve the policy’s quality at run time. This thesis considers two approximate POMDP solvers. One is a translation-based POMDP solver which converts a subclass of POMDP, called quasi-deterministic POMDP (QDET-POMDP) problems into classical planning problems or Markov decision processes (MDPs). The resulting approximate solution is either a contingency plan or an MDP policy that requires full observability of the world at run time. The other is a point-based POMDP solver which generates an approximate policy by utilizing sampling techniques. Study of the algorithms in simulation has shown that our execution monitoring approaches can improve the approximate POMDP solvers overall performance in terms of plan quality, plan generation time and plan execution time

Planning while Believing to Know

Over the last few years, the concept of Artificial Intelligence (AI) has become essential in our daily life and in several working scenarios. Among the various branches of AI, automated planning and the study of multi-agent systems are central research fields. This thesis focuses on a combination of these two areas: that is, a specialized kind of planning known as Multi-agent Epistemic Planning. This field of research is concentrated on all those scenarios where agents, reasoning in the space of knowledge/beliefs, try to find a plan to reach a desirable state from a starting one. This requires agents able to reason about her/his and others’ knowledge/beliefs and, therefore, capable of performing epistemic reasoning. Being aware of the information flows and the others’ states of mind is, in fact, a key aspect in several planning situations. That is why developing autonomous agents, that can reason considering the perspectives of their peers, is paramount to model a variety of real-world domains. The objective of our work is to formalize an environment where a complete characterization of the agents’ knowledge/beliefs interactions and updates are possible. In particular, we achieved such a goal by defining a new action-based language for Multi-agent Epistemic Planning and implementing epistemic planners based on it. These solvers, flexible enough to reason about various domains and different nuances of knowledge/belief update, can provide a solid base for further research on epistemic reasoning or real-base applications. This dissertation also proposes the design of a more general epistemic planning architecture. This architecture, following famous cognitive theories, tries to emulate some characteristics of the human decision-making process. In particular, we envisioned a system composed of several solving processes, each one with its own trade-off between efficiency and correctness, which are arbitrated by a meta-cognitive module