Problem Solving
A First-Order Formalization of Commitments and Goals for Planning
Meneguzzi, Felipe (Pontifical Catholic University of Rio Grande do Sul) | Telang, Pankaj R. (North Carolina State University) | Singh, Munindar P. (North Carolina State University)
Commitments help model interactions in multiagent systems in a computationally realizable yet high-level manner without compromising the autonomy and heterogeneity of the member agents. Recent work shows how to combine commitments with goals and apply planning methods to enable agents to determine their actions. However, previous approaches to modeling commitments are confined to propositional representations, which limits their applicability in practical cases. We propose a first-order representation and reasoning technique that accommodates templatic commitments and goals that may be applied repeatedly with differing bindings for domain objects. Doing so not only leads to a more perspicuous modeling, but also supports many practical patterns.
Steps Towards a Science of Heuristic Search
Wilt, Christopher Makoto (University of New Hampshire)
There are many algorithms designed to solve the shortest path problem. Each of the published algorithms has a demonstrated use; a situation in which it is the clear choice.ย Unfortunately, if faced with a novel problem, there is no reliable robust way to figure out which algorithm should be used to solve the new problem. When classifying things, the first step is to identify relevant features for classifications.ย In the context of heuristic search, it not clear what pieces of information should be used to predict search algorithm performance, and the question of algorithm selection for a novel domain is an open question. We first analyze which domain attributes common algorithms leverage, and discuss how to identify domains containing these attributes.ย In addition to discussing how to classify domains, we also discuss why the classifications matter for various algorithms.ย Ultimately, this will allow us to offer more accurate runtime predictions for various algorithms we analyze, allowing us to determine which algorithm will likely offer the best performance.
Reciprocal Hash Tables for Nearest Neighbor Search
Liu, Xianglong (Beihang University) | He, Junfeng (Columbia University andย Facebook) | Lang, Bo (Beihang University)
Recent years have witnessed the success of hashingtechniques in approximate nearest neighbor search. Inpractice, multiple hash tables are usually employed toretrieve more desired results from all hit buckets ofeach table. However, there are rare works studying theunified approach to constructing multiple informativehash tables except the widely used random way. In thispaper, we regard the table construction as a selectionproblem over a set of candidate hash functions. Withthe graph representation of the function set, we proposean efficient solution that sequentially applies normal-ized dominant set to finding the most informative andindependent hash functions for each table. To furtherreduce the redundancy between tables, we explore thereciprocal hash tables in a boosting manner, where thehash function graph is updated with high weights em-phasized on the misclassified neighbor pairs of previoushash tables. The construction method is general andcompatible with different types of hashing algorithmsusing different feature spaces and/or parameter settings.Extensive experiments on two large-scale benchmarksdemonstrate that the proposed method outperforms bothnaive construction method and state-of-the-art hashingalgorithms, with up to 65.93% accuracy gains.
Hypothesis Exploration for Malware Detection Using Planning
Sohrabi, Shirin (IBM T. J. Watson Research Center) | Udrea, Octavian (IBM T. J. Watson Research Center) | Riabov, Anton (IBM T. J. Watson Research Center)
In this paper we apply AI planning to address the hypothesis exploration problem and provide assistance to network administrators in detecting malware based on unreliable observations derived from network traffic.Building on the already established characterization and use of AI planning for similar problems, we propose a formulation of the hypothesis generation problem for malware detection as an AI planning problem with temporally extended goals and actions costs. Furthermore, we propose a notion of hypothesis ``plausibility'' under unreliable observations, which we model as plan quality. We then show that in the presence of unreliable observations, simply finding one most ``plausible'' hypothesis, although challenging, is not sufficient for effective malware detection. To that end, we propose a method for applying a state-of-the-art planner within a principled exploration process, to generate multiple distinct high-quality plans. We experimentally evaluate this approach by generating random problems of varying hardness both with respect to the number of observations, as well as the degree of unreliability. Based on these experiments, we argue that our approach presents a significant improvement over prior work that are focused on finding a single optimal plan, and that our hypothesis exploration application can motivate the development of new planners capable of generating the top high-quality plans.
Concurrent Reasoning with Inference Graphs
Schlegel, Daniel R. (University at Buffalo) | Shapiro, Stuart C. (University at Buffalo)
Since their popularity began to rise in the mid-2000s there has been significant growth in the number of multi-core and multi-processor computers available. Knowledge representation systems using logical inference have been slow to embrace this new technology. We present the concept of inference graphs, a natural deduction inference system which scales well on multi-core and multi-processor machines. Inference graphs enhance propositional graphs by treating propositional nodes as tasks which can be scheduled to operate upon messages sent between nodes via the arcs that already exist as part of the propositional graph representation. The use of scheduling heuristics within a prioritized message passing architecture allows inference graphs to perform very well in forward, backward, bi-directional, and focused reasoning. Tests demonstrate the usefulness of our scheduling heuristics, and show significant speedup in both best case and worst case inference scenarios as the number of processors increases.
Bidirectional Preference-Based Search for State Space Graph Problems
Galand, Lucie (University Paris Dauphine) | Ismaili, Anisse (University Pierre et Marie Curie) | Perny, Patrice (University Pierre et Marie Curie) | Spanjaard, Olivier (University Pierre et Marie Curie)
In multiobjective state space graph problems, each solution-path is evaluated by a cost vector. These cost vectors can be partially or completely ordered using a preference relation compatible with Pareto dominance. In this context, multiobjective preference-based search (MOPBS) aims at computing the preferred feasible solutions according to a predefined preference model, these preferred solutions being a subset (possibly the entire set) of Pareto optima. Standard algorithms for MOPBS perform a unidirectional search developing the search tree forward from the initial state to a goal state. Instead, in this paper, we focus on bidirectional search algorithms developing simultaneously one forward and one backward search tree. Although bi-directional search has been tested in various single objective problems, its efficiency in a multiobjective setting has never been studied. In this paper, we present several implementations of bidirectional preference-based search convenient for the multiobjective case and investigate their efficiency.
A Virtual Archive for the History of AI
Buchanan, Bruce G. (University of Pittsburgh) | Eckroth, Joshua (The Ohio State University) | Smith, Reid (Marathon Oil Corporation)
Publications that have influenced the growth of artificial intelligence are often difficult to obtain.ย We first collected titles of several thousand publications from many well-known sources and then selected about 1850 titles considered to be especially influential.ย We have identified, and in a few cases created, online versions of about half of these โclassics in AI.โย Searchable text of the documents enables additional analysis of trends and influences.ย Integration into the rest of the AITopics information portal contextualizes the classic publications.
The International โจGeneral Game Playing Competition
Genesereth, Michael (ย Stanford University) | Bjรถrnsson, Yngvi (Reykjavik University)
Games have played a prominent role as a test-bed for advancements in the field of Artificial Intelligence ever since its foundation over half a century ago, resulting in highly specialized world-class game-playing systems being developed for various games. The establishment of the International General Game Playing Competition in 2005, however, resulted in a renewed interest in more general problem solving approaches to game playing. In general game playing (GGP) the goal is to create game-playing systems that autonomously learn how to skillfully play a wide variety of games, given only the descriptions of the game rules. In this paper we review the history of the competition, discuss progress made so far, and list outstanding research challenges.
Cognitive Interpretation of Everyday Activities: Toward Perceptual Narrative Based Visuo-Spatial Scene Interpretation
Bhatt, Mehul, Suchan, Jakob, Schultz, Carl
We position a narrative-centred computational model for high-level knowledge representation and reasoning in the context of a range of assistive technologies concerned with "visuo-spatial perception and cognition" tasks. Our proposed narrative model encompasses aspects such as \emph{space, events, actions, change, and interaction} from the viewpoint of commonsense reasoning and learning in large-scale cognitive systems. The broad focus of this paper is on the domain of "human-activity interpretation" in smart environments, ambient intelligence etc. In the backdrop of a "smart meeting cinematography" domain, we position the proposed narrative model, preliminary work on perceptual narrativisation, and the immediate outlook on constructing general-purpose open-source tools for perceptual narrativisation. ACM Classification: I.2 Artificial Intelligence: I.2.0 General -- Cognitive Simulation, I.2.4 Knowledge Representation Formalisms and Methods, I.2.10 Vision and Scene Understanding: Architecture and control structures, Motion, Perceptual reasoning, Shape, Video analysis General keywords: cognitive systems; human-computer interaction; spatial cognition and computation; commonsense reasoning; spatial and temporal reasoning; assistive technologies
Bioclimating Modelling: A Machine Learning Perspective
Many machine learning (ML) approaches are widely used to generate bioclimatic models for prediction of geographic range of organism as a function of climate. Applications such as prediction of range shift in organism, range of invasive species influenced by climate change are important parameters in understanding the impact of climate change. However, success of machine learning-based approaches depends on a number of factors. While it can be safely said that no particular ML technique can be effective in all applications and success of a technique is predominantly dependent on the application or the type of the problem, it is useful to understand their behaviour to ensure informed choice of techniques. This paper presents a comprehensive review of machine learning-based bioclimatic model generation and analyses the factors influencing success of such models. Considering the wide use of statistical techniques, in our discussion we also include conventional statistical techniques used in bioclimatic modelling.