15 research outputs found
Structure and Complexity in Planning with Unary Operators
Unary operator domains -- i.e., domains in which operators have a single
effect -- arise naturally in many control problems. In its most general form,
the problem of STRIPS planning in unary operator domains is known to be as hard
as the general STRIPS planning problem -- both are PSPACE-complete. However,
unary operator domains induce a natural structure, called the domain's causal
graph. This graph relates between the preconditions and effect of each domain
operator. Causal graphs were exploited by Williams and Nayak in order to
analyze plan generation for one of the controllers in NASA's Deep-Space One
spacecraft. There, they utilized the fact that when this graph is acyclic, a
serialization ordering over any subgoal can be obtained quickly. In this paper
we conduct a comprehensive study of the relationship between the structure of a
domain's causal graph and the complexity of planning in this domain. On the
positive side, we show that a non-trivial polynomial time plan generation
algorithm exists for domains whose causal graph induces a polytree with a
constant bound on its node indegree. On the negative side, we show that even
plan existence is hard when the graph is a directed-path singly connected DAG.
More generally, we show that the number of paths in the causal graph is closely
related to the complexity of planning in the associated domain. Finally we
relate our results to the question of complexity of planning with serializable
subgoals
Representing problem-solving for knowledge refinement.
Knowledge refinement tools seek to correct faulty knowledge based systems (KBSs) by identifying and repairing potentially faulty rules. The goal of the KrustWorks project is to provide a source of refinement components from which specialised refinement tools tailored to the needs of a range of KBSs are built. A core refinement algorithm reasons about the knowledge that has been applied, but this approach demands general knowledge structures to represent the reasoning of a particular problem solving episode. This paper investigates some complex forms of rule interaction and defines a knowledge structure encompassing these. The approach has been applied to KBSs built in four shells and is demonstrated on a small example that incorporates some of the complexity found in real applications
The Divide-and-Conquer Subgoal-Ordering Algorithm for Speeding up Logic Inference
It is common to view programs as a combination of logic and control: the
logic part defines what the program must do, the control part -- how to do it.
The Logic Programming paradigm was developed with the intention of separating
the logic from the control. Recently, extensive research has been conducted on
automatic generation of control for logic programs. Only a few of these works
considered the issue of automatic generation of control for improving the
efficiency of logic programs. In this paper we present a novel algorithm for
automatic finding of lowest-cost subgoal orderings. The algorithm works using
the divide-and-conquer strategy. The given set of subgoals is partitioned into
smaller sets, based on co-occurrence of free variables. The subsets are ordered
recursively and merged, yielding a provably optimal order. We experimentally
demonstrate the utility of the algorithm by testing it in several domains, and
discuss the possibilities of its cooperation with other existing methods
Planning And Scheduling For Large-scaledistributed Systems
Many applications require computing resources well beyond those available on any single system. Simulations of atomic and subatomic systems with application to material science, computations related to study of natural sciences, and computer-aided design are examples of applications that can benefit from the resource-rich environment provided by a large collection of autonomous systems interconnected by high-speed networks. To transform such a collection of systems into a user\u27s virtual machine, we have to develop new algorithms for coordination, planning, scheduling, resource discovery, and other functions that can be automated. Then we can develop societal services based upon these algorithms, which hide the complexity of the computing system for users. In this dissertation, we address the problem of planning and scheduling for large-scale distributed systems. We discuss a model of the system, analyze the need for planning, scheduling, and plan switching to cope with a dynamically changing environment, present algorithms for the three functions, report the simulation results to study the performance of the algorithms, and introduce an architecture for an intelligent large-scale distributed system
Technological roadmap on AI planning and scheduling
At the beginning of the new century, Information Technologies had become basic and indispensable
constituents of the production and preparation processes for all kinds of goods and services and
with that are largely influencing both the working and private life of nearly every citizen. This
development will continue and even further grow with the continually increasing use of the Internet
in production, business, science, education, and everyday societal and private undertaking.
Recent years have shown, however, that a dramatic enhancement of software capabilities is required,
when aiming to continuously provide advanced and competitive products and services in all these
fast developing sectors. It includes the development of intelligent systems – systems that are more
autonomous, flexible, and robust than today’s conventional software.
Intelligent Planning and Scheduling is a key enabling technology for intelligent systems. It has
been developed and matured over the last three decades and has successfully been employed for a
variety of applications in commerce, industry, education, medicine, public transport, defense, and
government.
This document reviews the state-of-the-art in key application and technical areas of Intelligent Planning
and Scheduling. It identifies the most important research, development, and technology transfer
efforts required in the coming 3 to 10 years and shows the way forward to meet these challenges in
the short-, medium- and longer-term future.
The roadmap has been developed under the regime of PLANET – the European Network of Excellence
in AI Planning. This network, established by the European Commission in 1998, is the co-ordinating
framework for research, development, and technology transfer in the field of Intelligent Planning and
Scheduling in Europe.
A large number of people have contributed to this document including the members of PLANET non-
European international experts, and a number of independent expert peer reviewers. All of them are
acknowledged in a separate section of this document.
Intelligent Planning and Scheduling is a far-reaching technology. Accepting the challenges and progressing
along the directions pointed out in this roadmap will enable a new generation of intelligent
application systems in a wide variety of industrial, commercial, public, and private sectors