title: New Options for Hoeffding Trees

authors: Pfahringer, Bernhard

subjects: computer science

abstract: Hoeffding trees are state-of-the-art for processing high-speed data streams. Their ingenuity stems from updating sufficient statistics, only addressing growth when decisions can be made that are guaranteed to be almost identical to those that would be made by conventional batch learning methods. Despite this guarantee, decisions are still subject to limited lookahead and stability issues. In this paper we explore Hoeffding Option Trees, a regular Hoeffding tree containing additional option nodes that allow several tests to be applied, leading to multiple Hoeffding trees as separate paths. We show how to control tree growth in order to generate a mixture of paths, and empirically determine a reasonable number of paths. We then empirically evaluate a spectrum of Hoeffding tree variations: single trees, option trees and bagged trees. Finally, we investigate pruning. We show that on some datasets a pruned option tree can be smaller and more accurate than a single tree.

text: New Options for Hoeffding Trees Hoeffding trees are state-of-the-art for processing high-speed data streams. Their ingenuity stems from updating sufficient statistics, only addressing growth when decisions can be made that are guaranteed to be almost identical to those that would be made by conventional batch learning methods. Despite this guarantee, decisions are still subject to limited lookahead and stability issues. In this paper we explore Hoeffding Option Trees, a regular Hoeffding tree containing additional option nodes that allow several tests to be applied, leading to multiple Hoeffding trees as separate paths. We show how to control tree growth in order to generate a mixture of paths, and empirically determine a reasonable number of paths. We then empirically evaluate a spectrum of Hoeffding tree variations: single trees, option trees and bagged trees. Finally, we investigate pruning. We show that on some datasets a pruned option tree can be smaller and more accurate than a single tree.

year: 2007

title: The relation between preference and demand for litter substrates in the domestic hen

authors: Harris, Aimee Rebecca

subjects: preference

abstract: Six hen's preferences between 5-min access to each of two litter substrates, sand and sawdust, were measured using dependent concurrent VI 60 s VI 60 s schedules of reinforcement.  The obtained preferences were small and idiosyncratic.  Demand functions were generated separately for each of the two substrates by requiring the hens to perform under increasing FR schedules.  The demand functions were disorderly, some were linear, some were of mixed elasticity, and others curved upwards.  No clear relation between the individual hens' preference and demand measures was found.  The overall response rates, running response rates and average post-reinforcement pause durations were atypical compared to previous demand research, possibly due to low levels of reinforcer collection, but were similar for individual subjects in both demand conditions.  During the demand assessment, dustbathing took place in a similar proportion of reinforcers for each substrate.  During the preference assessment, a greater proportion of dustbathing took place during sand reinforcers.  Individual hens did not consistently dustbathe more in their preferred substrate.  It was argued that the inconclusive results were a product of the substrates used.  The atypical demand functions, response rates and average PRP durations may have been due to behaviour that was not schedule related occurring during key time (i.e., the subjects may have been continuing a dustbathing bout).  It is possible, that the two substrates were too similar, and thus the subjects did not have a clear preference for one over the other.  In future research preference should be assessed prior to demand, to ensure a clear preference can be obtained, with reinforcers that are qualitatively more different than those used in the present experiment.

text: The relation between preference and demand for litter substrates in the domestic hen Six hen's preferences between 5-min access to each of two litter substrates, sand and sawdust, were measured using dependent concurrent VI 60 s VI 60 s schedules of reinforcement.  The obtained preferences were small and idiosyncratic.  Demand functions were generated separately for each of the two substrates by requiring the hens to perform under increasing FR schedules.  The demand functions were disorderly, some were linear, some were of mixed elasticity, and others curved upwards.  No clear relation between the individual hens' preference and demand measures was found.  The overall response rates, running response rates and average post-reinforcement pause durations were atypical compared to previous demand research, possibly due to low levels of reinforcer collection, but were similar for individual subjects in both demand conditions.  During the demand assessment, dustbathing took place in a similar proportion of reinforcers for each substrate.  During the preference assessment, a greater proportion of dustbathing took place during sand reinforcers.  Individual hens did not consistently dustbathe more in their preferred substrate.  It was argued that the inconclusive results were a product of the substrates used.  The atypical demand functions, response rates and average PRP durations may have been due to behaviour that was not schedule related occurring during key time (i.e., the subjects may have been continuing a dustbathing bout).  It is possible, that the two substrates were too similar, and thus the subjects did not have a clear preference for one over the other.  In future research preference should be assessed prior to demand, to ensure a clear preference can be obtained, with reinforcers that are qualitatively more different than those used in the present experiment.

year: 2006

title: An AR memory app based on Māori mnemonic aids

authors: Taia, Ivy

subjects: computer science

abstract: Traumatic Brain Injury (TBI) is a world-wide “silent epidemic” causing a variety of memory issues for those affected. Although several software approaches aim to aid memory recollection, they are inadequate for many TBI survivors and none address aspects of cultural awareness in New Zealand. We explored design concepts of traditional Māori cultural tools / techniques and how they helped Māori people recall past information. This paper describes our research and development of Maumahara Papahou, a mobile app that uses Augmented Reality features to create a digital memory treasure box based on the concepts of Māori mnemonic aids.

text: An AR memory app based on Māori mnemonic aids Traumatic Brain Injury (TBI) is a world-wide “silent epidemic” causing a variety of memory issues for those affected. Although several software approaches aim to aid memory recollection, they are inadequate for many TBI survivors and none address aspects of cultural awareness in New Zealand. We explored design concepts of traditional Māori cultural tools / techniques and how they helped Māori people recall past information. This paper describes our research and development of Maumahara Papahou, a mobile app that uses Augmented Reality features to create a digital memory treasure box based on the concepts of Māori mnemonic aids.

year: 2018