Peter Vamplew

Peter Vamplew
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Peter verified their affiliation via an institutional email.
Verified
Peter verified their affiliation via an institutional email.
  • B.A., B Sc. (Hons), PhD
  • Professor at Federation University

Researching multi-objective reinforcement learning, including its value for creating human-aligned AI.

About

154
Publications
66,471
Reads
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4,977
Citations
Introduction
My interests lie broadly in the area of artificial intelligence. In particular I am interested in the creation of autonomous learning agents using reinforcement learning methods, and I have a specific focus on the extension and application of reinforcement learning to problems involving multiple competing objectives. More recently I have developed an interest in the technical issues around creating human-aligned AI, including safety, ethics, explainability and trust.
Current institution
Federation University
Current position
  • Professor
Additional affiliations
January 2013 - July 2014
Federation University
Position
  • Associate Professor; Associate Dean, Research
December 2005 - December 2013
Federation University
Position
  • Professor (Associate)
January 1991 - November 2005
University of Tasmania
Position
  • Lecturer

Publications

Publications (154)
Article
The concept of impact-minimisation has previously been proposed as an approach to addressing the safety concerns that can arise from utility-maximising agents. An impact-minimising agent takes into account the potential impact of its actions on the state of the environment when selecting actions, so as to avoid unacceptable side-effects. This paper...
Article
Full-text available
A common approach to address multiobjective problems using reinforcement learning methods is to extend model-free, value-based algorithms such as Q-learning to use a vector of Q-values in combination with an appropriate action selection mechanism that is often based on scalarisation. Most prior empirical evaluation of these approaches has focused o...
Article
Full-text available
Interactive reinforcement learning methods utilise an external information source to evaluate decisions and accelerate learning. Previous work has shown that human advice could significantly improve learning agents’ performance. When evaluating reinforcement learning algorithms, it is common to repeat experiments as parameters are altered or to gai...
Article
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This paper introduces a new scalable multi-objective deep reinforcement learning (MODRL) framework based on deep Q-networks. We develop a high-performance MODRL framework that supports both single-policy and multi-policy strategies, as well as both linear and non-linear approaches to action selection. The experimental results on two benchmark probl...
Chapter
Reinforcement learning (RL) is a learning approach based on behavioral psychology used by artificial agents to learn autonomously by interacting with their environment. An open issue in RL is the lack of visibility and understanding for end-users in terms of decisions taken by an agent during the learning process. One way to overcome this issue is...
Preprint
Full-text available
Real-world sequential decision-making tasks often require balancing trade-offs between multiple conflicting objectives, making Multi-Objective Reinforcement Learning (MORL) an increasingly prominent field of research. Despite recent advances, existing MORL literature has narrowly focused on performance within static environments, neglecting the imp...
Preprint
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Apologies are a powerful tool used in human-human interactions to provide affective support, regulate social processes, and exchange information following a trust violation. The emerging field of AI apology investigates the use of apologies by artificially intelligent systems, with recent research suggesting how this tool may provide similar value...
Preprint
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Emerging research in Pluralistic Artificial Intelligence (AI) alignment seeks to address how intelligent systems can be designed and deployed in accordance with diverse human needs and values. We contribute to this pursuit with a dynamic approach for aligning AI with diverse and shifting user preferences through Multi Objective Reinforcement Learni...
Preprint
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Reinforcement learning (RL) is a valuable tool for the creation of AI systems. However it may be problematic to adequately align RL based on scalar rewards if there are multiple conflicting values or stakeholders to be considered. Over the last decade multi-objective reinforcement learning (MORL) using vector rewards has emerged as an alternative t...
Article
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Toxic behavior has been impacting players in online multiplayer environments since their inception. Griefing is a type of toxic behavior that focuses on player-to-player in-game disruption and is quite prevalent. However, research into the extent of the impact is still scarce. The present study investigated the impact on the psychological needs of...
Article
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This paper describes a language wrapper for the NetHack Learning Environment (NLE) [1]. The wrapper replaces the non-language observations and actions with comparable language versions. The NLE offers a grand challenge for AI research while MiniHack [2] extends this potential to more specific and configurable tasks. By providing a language interfac...
Preprint
Full-text available
The rapid advancement of artificial intelligence (AI) systems suggests that artificial general intelligence (AGI) systems may soon arrive. Many researchers are concerned that AIs and AGIs will harm humans via intentional misuse (AI-misuse) or through accidents (AI-accidents). In respect of AI-accidents, there is an increasing effort focused on deve...
Article
Full-text available
For an Artificially Intelligent (AI) system to maintain alignment between human desires and its behaviour, it is important that the AI account for human preferences. This paper proposes and empirically evaluates the first approach to aligning agent behaviour to human preference via an apologetic framework. In practice, an apology may consist of an...
Article
Full-text available
Broad-XAI moves away from interpreting individual decisions based on a single datum and aims to provide integrated explanations from multiple machine learning algorithms into a coherent explanation of an agent’s behaviour that is aligned to the communication needs of the explainee. Reinforcement Learning (RL) methods, we propose, provide a potentia...
Conference Paper
Full-text available
Real-world sequential decision-making tasks are usually complex , and require trade-offs between multiple-often conflicting-objectives. However, the majority of research in reinforcement learning (RL) and decision-theoretic planning assumes a single objective, or that multiple objectives can be handled via a predefined weighted sum over the objecti...
Preprint
Full-text available
The use of interactive advice in reinforcement learning scenarios allows for speeding up the learning process for autonomous agents. Current interactive reinforcement learning research has been limited to real-time interactions that offer relevant user advice to the current state only. Moreover, the information provided by each interaction is not r...
Preprint
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Deep Q-Networks algorithm (DQN) was the first reinforcement learning algorithm using deep neural network to successfully surpass human level performance in a number of Atari learning environments. However, divergent and unstable behaviour have been long standing issues in DQNs. The unstable behaviour is often characterised by overestimation in the...
Article
Full-text available
The recent paper “Reward is Enough” by Silver, Singh, Precup and Sutton posits that the concept of reward maximisation is sufficient to underpin all intelligence, both natural and artificial, and provides a suitable basis for the creation of artificial general intelligence. We contest the underlying assumption of Silver et al. that such reward can...
Preprint
Full-text available
Explainable artificial intelligence is a research field that tries to provide more transparency for autonomous intelligent systems. Explainability has been used, particularly in reinforcement learning and robotic scenarios, to better understand the robot decision-making process. Previous work, however, has been widely focused on providing technical...
Article
Conventional reinforcement learning focuses on problems with single objective. However, many problems have multiple objectives or criteria that may be independent, related, or contradictory. In such cases, multi-objective reinforcement learning is used to propose a compromise among the solutions to balance the objectives. TOPSIS is a multi-criteria...
Article
Full-text available
Real-world sequential decision-making tasks are generally complex, requiring trade-offs between multiple, often conflicting, objectives. Despite this, the majority of research in reinforcement learning and decision-theoretic planning either assumes only a single objective, or that multiple objectives can be adequately handled via a simple linear co...
Article
Full-text available
Neural networks are effective function approximators, but hard to train in the reinforcement learning (RL) context mainly because samples are correlated. In complex problems, a neural RL approach is often able to learn a better solution than tabular RL, but generally takes longer. This paper proposes two methods, Discrete-to-Deep Supervised Policy...
Article
Full-text available
Interactive reinforcement learning proposes the use of externally sourced information in order to speed up the learning process. When interacting with a learner agent, humans may provide either evaluative or informative advice. Prior research has focused on the effect of human-sourced advice by including real-time feedback on the interactive reinfo...
Preprint
Full-text available
The recent paper `"Reward is Enough" by Silver, Singh, Precup and Sutton posits that the concept of reward maximisation is sufficient to underpin all intelligence, both natural and artificial. We contest the underlying assumption of Silver et al. that such reward can be scalar-valued. In this paper we explain why scalar rewards are insufficient to...
Article
Full-text available
A long-term goal of reinforcement learning agents is to be able to perform tasks in complex real-world scenarios. The use of external information is one way of scaling agents to more complex problems. However, there is a general lack of collaboration or interoperability between different approaches using external information. In this work, while re...
Article
Full-text available
Interactive reinforcement learning has allowed speeding up the learning process in autonomous agents by including a human trainer providing extra information to the agent in real-time. Current interactive reinforcement learning research has been limited to real-time interactions that offer relevant user advice to the current state only. Additionall...
Article
Full-text available
Robotic systems are more present in our society everyday. In human–robot environments, it is crucial that end-users may correctly understand their robotic team-partners, in order to collaboratively complete a task. To increase action understanding, users demand more explainability about the decisions by the robot in particular situations. Recently,...
Preprint
Full-text available
Broad Explainable Artificial Intelligence moves away from interpreting individual decisions based on a single datum and aims to provide integrated explanations from multiple machine learning algorithms into a coherent explanation of an agent's behaviour that is aligned to the communication needs of the explainee. Reinforcement Learning (RL) methods...
Article
Full-text available
An increasing number of complex problems have naturally posed significant challenges in decision-making theory and reinforcement learning practices. These problems often involve multiple conflicting reward signals that inherently cause agents’ poor exploration in seeking a specific goal. In extreme cases, the agent gets stuck in a sub-optimal solut...
Preprint
Full-text available
Over the last few years there has been rapid research growth into eXplainable Artificial Intelligence (XAI) and the closely aligned Interpretable Machine Learning (IML). Drivers for this growth include recent legislative changes and increased investments by industry and governments, along with increased concern from the general public. People are a...
Article
Over the last few years there has been rapid research growth into eXplainable Artificial Intelligence (XAI) and the closely aligned Interpretable Machine Learning (IML). Drivers for this growth include recent legislative changes and increased investments by industry and governments, along with increased concern from the general public. People are a...
Preprint
Full-text available
Real-world decision-making tasks are generally complex, requiring trade-offs between multiple, often conflicting, objectives. Despite this, the majority of research in reinforcement learning and decision-theoretic planning either assumes only a single objective, or that multiple objectives can be adequately handled via a simple linear combination....
Preprint
Interactive reinforcement learning has allowed speeding up the learning process in autonomous agents by including a human trainer providing extra information to the agent in real-time. Current interactive reinforcement learning research has been limited to interactions that offer relevant advice to the current state only. Additionally, the informat...
Chapter
Many types of malicious software are controlled from an attacker’s command and control (C2) servers. Anti-virus organizations seek to defeat malware attacks by requesting removal of C2 server Domain Name Server (DNS) records. As a result, the life span of most malware samples is relatively short. Large datasets of historical malware samples are ava...
Chapter
Ransomware is a widespread class of malware that encrypts files in a victim’s computer and extorts victims into paying a fee to regain access to their data. Previous research has proposed methods for ransomware detection using machine learning techniques. However, this research has not examined the precision of ransomware detection. While existing...
Preprint
Full-text available
Reinforcement learning is an approach used by intelligent agents to autonomously learn new skills. Although reinforcement learning has been demonstrated to be an effective learning approach in several different contexts, a common drawback exhibited is the time needed in order to satisfactorily learn a task, especially in large state-action spaces....
Article
Full-text available
Finding changed and similar functions between a pair of binaries is an important problem in malware attribution and for the identification of new malware capabilities. This paper presents a new technique called Function Similarity using Family Context (FSFC) for this problem. FSFC trains a Support Vector Machine (SVM) model using pairs of similar f...
Preprint
Full-text available
A long-term goal of reinforcement learning agents is to be able to perform tasks in complex real-world scenarios. The use of external information is one way of scaling agents to more complex problems. However, there is a general lack of collaboration or interoperability between different approaches using external information. In this work, we propo...
Presentation
Full-text available
Presentation: 20th Industrial Conference on Data Mining: ICDM 2020 Paper: Unified Expression Ripple Down Rules based Fraud Detection Technique for Scalable Data
Preprint
Full-text available
Robotic systems are more present in our society every day. In human-robot interaction scenarios, it is crucial that end-users develop trust in their robotic team-partners, in order to collaboratively complete a task. To increase trust, users demand more understanding about the decisions by the robot in particular situations. Recently, explainable r...
Preprint
Neural networks are effective function approximators, but hard to train in the reinforcement learning (RL) context mainly because samples are correlated. For years, scholars have got around this by employing experience replay or an asynchronous parallel-agent system. This paper proposes Discrete-to-Deep Supervised Policy Learning (D2D-SPL) for trai...
Preprint
Full-text available
We report a previously unidentified issue with model-free, value-based approaches to multiobjective reinforcement learning in the context of environments with stochastic state transitions. An example multiobjective Markov Decision Process (MOMDP) is used to demonstrate that under such conditions these approaches may be unable to discover the policy...
Chapter
Full-text available
The performance of machine learning models can be improved in a variety of ways including segmentation, treating missing and outlier values, feature engineering, feature selection, multiple algorithms, algorithm tuning/compactness and ensemble methods. Feature engineering and compactness of the model can have a significant impact on the algorithm’s...
Article
Full-text available
Cyberttacks are becoming increasingly sophisticated, necessitating the efficient intrusion detection mechanisms to monitor computer resources and generate reports on anomalous or suspicious activities. Many Intrusion Detection Systems (IDSs) use a single classifier for identifying intrusions. Single classifier IDSs are unable to achieve high accura...
Conference Paper
Full-text available
Fraud detection for online banking is an important research area and higher accuracy is highly desirable. The main challenges in fraud analysis are due to the presence of heterogeneous transactions data, large and distributed data. Among existing rule-based techniques for fraud detection, Ripple Down Rules (RDR) is ideal due to its less maintenance...
Article
Full-text available
Cyber-attacks are becoming more sophisticated and thereby presenting increasing challenges in accurately detecting intrusions. Failure to prevent the intrusions could degrade the credibility of security services, e.g. data confidentiality, integrity, and availability. Numerous intrusion detection methods have been proposed in the literature to tack...
Chapter
Reinforcement learning techniques for solving complex problems are resource-intensive and take a long time to converge, prompting a need for methods that encourage faster learning. In this paper we show our successful application of actor-critic reinforcement learning to the air combat simulation domain and how reward structures affect the learning...
Article
Full-text available
The Internet of Things (IoT) has been rapidly evolving towards making a greater impact on everyday life to large industrial systems. Unfortunately, this has attracted the attention of cybercriminals who made IoT a target of malicious activities, opening the door to a possible attack to the end nodes. Due to the large number and diverse types of IoT...
Thesis
Full-text available
Reinforcement Learning (RL) has seen increasing interest over the past few years, partially owing to breakthroughs in the digestion and application of external information. The use of external information results in improved learning speeds and solutions to more complex domains. This thesis, a collection of five key contributions, demonstrates that...
Conference Paper
Full-text available
Gene Regulatory Networks (GRNs) offer enhanced insight into the biological functions and biochemical pathways of cells associated with gene regulatory mechanisms. However, obtaining accurate GRNs that explain gene expressions and functional associations remains a difficult task. Only a few studies have incorporated heuristics into a GRN discovery p...
Chapter
Full-text available
Fraud detection for online banking is an important research area, but one of the challenges is the heterogeneous nature of transactions data i.e. a combination of numeric as well as mixed attributes. Usually, numeric format data gives better performance for classification, regression and clustering algorithms. However, many machine learning problem...
Data
These are simple artificial datasets used to compare the performance of neural regression algorithms on data where the output is a function of the input, and data where the output is not a function of the input (i.e. where the number of outputs may vary, depending on the value of input). These are the datasets used in our forthcoming paper "Non-Fun...
Article
This work identifies an important, previously unaddressed issue for regression based on neural networks – learning to accurately approximate problems where the output is not a function of the input (i.e. where the number of outputs required varies across input space). Such non-functional regression problems arise in a number of applications, and ca...
Chapter
Due to increase in intrusion activities over internet, many intrusion detection systems are proposed to detect abnormal activities, but most of these detection systems suffer a common problem which is producing a high number of alerts and a huge number of false positives. As a result, normal activities could be classified as intrusion activities. T...
Chapter
Integrated Prudence Analysis has been proposed as a method to maximize the accuracy of rule based systems. The paper presents evaluation results of the three Prudence methods on public datasets which demonstrate that combining attribute-based and structural Prudence produces a net improvement in Prudence Accuracy.
Article
Full-text available
SoniFight is utility software designed to provide additional sonification cues to video games, especially those in the fighting game genre, in order to enhance their accessibility for players who are blind or visually impaired. While the software is distributed with configuration files that add sonification to a number of popular video games, confi...
Chapter
https://link.springer.com/referenceworkentry/10.1007/978-3-319-08234-9_200-1 With the success of the MMORPG genre, griefing has become an extremely pervasive problem with differing levels of intensity for each griefing incident, and it needs to be addressed. In this article, definitions for MMORPGs, griefing, and the instigators of griefing, calle...
Article
Full-text available
As the capabilities of artificial intelligence systems improve, it becomes important to constrain their actions to ensure their behaviour remains beneficial to humanity. A variety of ethical, legal and safety-based frameworks have been proposed as a basis for designing these constraints. Despite their variations, these frameworks share the common c...
Article
Full-text available
The original version of this article unfortunately contained a mistake. The family name and the e-mail address of the first author had been incorrectly written as Leigh Achternbosch (l.achternbosch@federation.edu.au) instead of Leigh Achterbosch (l.achterbosch@federation.edu.au).
Article
Full-text available
Through the ethnographic method of participant observation in World of Warcraft, this paper aims to document various actions that may be considered griefing among the Massively Multiplayer Online Role-Playing Game (MMORPG) community. Griefing as a term can be very subjective, so witnessing the antisocial and intentional actions first-hand can be us...
Conference Paper
Conventional Knowledge-Based Systems (KBS) have no way of detecting or signalling when their knowledge is insufficient to handle a case. Consequently, these systems may produce an uninformed conclusion when presented with a case beyond their current knowledge (brittleness) which results in the KBS giving incorrect conclusions due to insufficient kn...
Article
Full-text available
Many real-life problems involve dealing with multiple objectives. For example, in network routing the criteria may consist of energy consumption, latency, and channel capacity, which are in essence conflicting objectives. As in many problems there may be multiple (conflicting) objectives, there usually does not exist a single optimal solution. In t...
Article
For reinforcement learning tasks with multiple objectives, it may be advantageous to learn stochastic or non-stationary policies. This paper investigates two novel algorithms for learning non-stationary policies which produce Pareto-optimal behaviour (w-steering and Q-steering), by extending prior work based on the concept of geometric steering. Em...
Article
Despite growing interest over recent years in applying reinforcement learning to multiobjective problems, there has been little research into the applicability and effectiveness of exploration strategies within the multiobjective context. This work considers several widely-used approaches to exploration from the single-objective reinforcement learn...
Conference Paper
The CRISP-DM methodology is commonly used in data analytics exercises within an organisation to provide system and structure to data mining processes. However, in providing a rigorous framework, CRISP-DM overlooks two facets of data analytics in organisational contexts; data mining exercises are far more agile and subject to change than presumed in...
Article
Full-text available
There is an anti-social phenomenon known as griefing that occurs in online games. Griefing refers to the act of one player intentionally disrupting another player’s game experience for personal pleasure and possibly potential gain. Achterbosch [2015. “Causes, Magnitude and Implications of Griefing in Massively Multiplayer Online Role-Playing Games....
Poster
Full-text available
CALL FOR PAPERS AAMAS 2017 Workshop on Multi-Objective Decision Making (MODeM 2017)
Article
Full-text available
Background: Gene Regulatory Networks (GRNs) offer enhanced insight into the biological functions and biochemical pathways of cells associated with gene regulatory mechanisms. However, obtaining accurate GRNs that explain gene expressions and functional associations still remains a difficult task. Only a few studies have incorporated heuristics into...
Conference Paper
Full-text available
Frauds are dramatically increasing every year, resulting in billions of dollars in losses around the globe mainly to banks. One of the key limitations in advancing research in the area of fraud detection is the unwillingness of banks to share statistics and datasets about this fraud to the public due to privacy concerns. To overcome these shortcomi...
Conference Paper
Full-text available
Genome-wide association studies (GWAS) and next-generation sequencing (NGS) has led to an increase in information about the human genome and cardiovascular disease. Understanding the role of genes in cardiac function and pathology requires modeling gene interactions and identification of regulatory genes as part of a gene regulatory network (GRN)....
Article
Full-text available
The Caliko library is an implementation of the FABRIK (Forward And Backward Reaching Inverse Kinematics) algorithm written in Java. The inverse kinematics (IK) algorithm is implemented in both 2D and 3D, and incorporates a variety of joint constraints as well as the ability to connect multiple IK chains together in a hierarchy. The library allows f...
Presentation
Full-text available
Provides an overview of the motivating scenarios for multiobjective reinforcement learning (MORL), some speculation about how MORL may assist in implementing ethically constrained AI, and a guide to existing MORL algorithms and remaining challenges and promising areas for MORL research.
Conference Paper
There has been little research into multiobjective reinforcement learning (MORL) algorithms using stochastic or non-stationary policies, even though such policies may Pareto-dominate deterministic stationary policies. One approach is steering which forms a non-stationary combination of deterministic stationary base policies. This paper presents two...
Conference Paper
Full-text available
We argue that multi-objective methods are underrepresented in RL research, and present three scenarios to justify the need for explicitly multi-objective approaches. Key to these scenarios is that although the utility the user derives from a policy — which is what we ultimately aim to optimize — is scalar, it is sometimes impossible, undesirable or...
Conference Paper
Full-text available
Value-based approaches to reinforcement learning (RL) maintain a value function that measures the long term utility of a state or state-action pair. A long standing issue in RL is how to create a finite representation in a continuous, and therefore infinite, state environment. The common approach is to use function approximators such as tile coding...
Article
Full-text available
Fed up with repeated spam emails from faux journals seeking submissions, I decided to have some fun; the results were initially amusing, but ultimately concerning. Note: I only have access to this paper in image format, so have included an OCRed version of the text below: As a computer science researcher,I first encountered predatory, spam-driven...
Article
Full-text available
‘Griefing’ is a term used to describe when a player within a multiplayer online environment intentionally disrupts another player’s game experience for his or her own personal enjoyment or gain. Every day a certain percentage of users of Massively Multiplayer Online Role-Playing Games (MMORPG) are experiencing some form of griefing. There have been...
Article
Full-text available
Sequential decision-making problems with multiple objectives arise naturally in practice and pose unique challenges for research in decision-theoretic planning and learning, which has largely focused on single-objective settings. This article surveys algorithms designed for sequential decision-making problems with multiple objectives. Though there...
Article
A useful patient admission prediction model that helps the emergency department of a hospital admit patients efficiently is of great importance. It not only improves the care quality provided by the emergency department but also reduces waiting time of patients. This paper proposes an automatic prediction method for patient admission based on a fuz...
Conference Paper
Every day in online games designed to entertain, an unknown percentage of users are experiencing what is known as 'Griefing'. Griefing is used to describe when a player within a multiplayer online environment intentionally disrupts another player's game experience for his/her own personal enjoyment or material gain. Unrestrained, griefing could lea...
Article
Full-text available
One reason for video game classification is to provide information for parents to enable them to make informed game choices for their children. The highest classification level in Australia is MA15+, and many games rated for age 17 and 18 overseas are placed into this category. Research shows that in the USA, classification information for games do...
Conference Paper
In this paper we provide empirical data of the performance of the two most commonly used multiobjective reinforcement learning algorithms against a set of benchmarks. First, we describe a methodology that was used in this paper. Then, we carefully describe the details and properties of the proposed problems and how those properties influence the be...
Conference Paper
Presenting a novel way using a games-based approach to teach immunology to undergraduate science students.
Conference Paper
Full-text available
Most commercial Fraud Detection components of Internet banking systems use some kind of hybrid setup usually comprising a Rule-Base and an Artificial Neural Network. Such rule bases have been criticised for a lack of innovation in their approach to Knowledge Acquisition and maintenance. Furthermore, the systems are brittle; they have no way of know...
Conference Paper
Rated Multiple Classification Ripple Down Rules (RM) and Ripple Down Models (RDM) are two of the successful prudent RDR approaches published. To date, there has not been a published, dedicated comparison of the two. This paper presents a systematic preliminary evaluation and analysis of the two techniques. The tests and results reported in this pap...
Article
This study empirically evaluates the effectiveness of different feature types for the classification of the first language of an author. In particular, it examines the utility of psycholinguistic features, extracted by the Linguistic Inquiry and Word Count (LIWC) tool, that have not previously been applied to the task of author profiling. As LIWC i...
Article
The process of sleep stage identification is a labour-intensive task that involves the specialized interpretation of the polysomnographic signals captured from a patient’s overnight sleep session. Automating this task has proven to be challenging for data mining algorithms because of noise, complexity and the extreme size of data. In this paper we...
Article
This chapter describes a novel multistage method for linguistic clustering of large collections of texts available on the Internet as a precursor to linguistic analysis of these texts. This method addresses the practicalities of applying clustering operations to a very large set of text documents by using a combination of unsupervised clustering an...
Conference Paper
Robocup is a popular test bed for AI programs around the world. Robosoccer is one of the two major parts of Robocup, in which AIBO entertainment robots take part in the middle sized soccer event. The three key challenges that robots need to face in this event are manoeuvrability, image recognition and decision making skills. This paper focuses on t...

Questions

Question (1)
Question
Does anyone know of a function approximator which can produce a variable number of output values (i.e. for some regions in input space it might output a vector of 3 values, whereas in other regions it might produce 5 outputs)?
Update: Thanks everyone for your suggestions. I realise now that I missed a critical aspect when phrasing my original question - we don't know in advance how many outputs will be required in each region of the input space (or even what the regions of the input space are). So maybe, I should rephrase my question in light of Simone and Meysar's answers - is there a function approximator which can learn to produce a single output for some parts of input space, and no output for other parts? My thinking so far is to use something like an RBF network as suggested by Vassilis, with a threshold applied so no output is produced if the input doesn't closely match any of the basis functions.

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