title: Learning language using genetic algorithms

authors: Smith, Tony C.

subjects: computer science

abstract: Strict pattern-based methods of grammar induction are often frustrated by the apparently inexhaustible variety of novel word combinations in large corpora. Statistical methods offer a possible solution by allowing frequent well-formed expressions to overwhelm the infrequent ungrammatical ones. They also have the desirable property of being able to construct robust grammars from positive instances alone. Unfortunately, the  zero-frequency  problem entails assigning a small probability to all possible word patterns, thus ungrammatical n-grams become as probable as unseen grammatical ones. Further, such grammars are unable to take advantage of inherent lexical properties that should allow infrequent words to inherit the syntactic properties of the class to which they belong. 
This paper describes a genetic algorithm (GA) that adapts a population of hypothesis grammars towards a more effective model of language structure. The GA is statistically sensitive in that the utility of frequent patterns is reinforced by the persistence of efficient substructures. It also supports the view of language learning as a  bootstrapping problem,  a learning domain where it appears necessary to simultaneously discover a set of categories and a set of rules defined over them. Results from a number of tests indicate that the GA is a robust, fault-tolerant method for inferring grammars from positive examples of natural language.

text: Learning language using genetic algorithms Strict pattern-based methods of grammar induction are often frustrated by the apparently inexhaustible variety of novel word combinations in large corpora. Statistical methods offer a possible solution by allowing frequent well-formed expressions to overwhelm the infrequent ungrammatical ones. They also have the desirable property of being able to construct robust grammars from positive instances alone. Unfortunately, the  zero-frequency  problem entails assigning a small probability to all possible word patterns, thus ungrammatical n-grams become as probable as unseen grammatical ones. Further, such grammars are unable to take advantage of inherent lexical properties that should allow infrequent words to inherit the syntactic properties of the class to which they belong. 
This paper describes a genetic algorithm (GA) that adapts a population of hypothesis grammars towards a more effective model of language structure. The GA is statistically sensitive in that the utility of frequent patterns is reinforced by the persistence of efficient substructures. It also supports the view of language learning as a  bootstrapping problem,  a learning domain where it appears necessary to simultaneously discover a set of categories and a set of rules defined over them. Results from a number of tests indicate that the GA is a robust, fault-tolerant method for inferring grammars from positive examples of natural language.

year: 1996

title: Spectroscopic and synthetic studies of lichen metabolites

authors: Ronaldson, Kathlyn Joy

abstract: Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

text: Spectroscopic and synthetic studies of lichen metabolites Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

year: 1980

title: “Landlords wouldn’t give my application a second look.” Discrimination exacerbates inequalities in access to private rental housing

authors: Terruhn, Jessica

abstract: This report and the key insights are based on findings from a housing survey that was conducted with 800 residents in neighbourhoods in Auckland, Hamilton and Christchurch. 
• Perceptions of unfairness in Aotearoa’s housing sector are widespread. Renters, Māori, younger people and low-income groups as well as residents in neighbourhoods with high levels of housing deprivation are most likely to think that people are treated unfairly when trying to rent or buy a home in Aotearoa. 
• Nearly one in three respondents reported having experienced discrimination when trying to rent or buy a home in Aotearoa. Renters, Māori, younger people and low-income groups as well as residents in neighbourhoods with high levels of housing deprivation are most likely to report experiences of discrimination. 
• Advantage and disadvantage in securing a home are determined by a combination of interlocking factors, including income and employment status, age, family status, and race/ethnicity or skin colour. These patterns suggest widespread experiences of potentially unlawful housing discrimination. 
• People strategically try to avoid and mitigate discrimination. Expectations of being discriminated against and of being advantaged influence where and how home seekers search for housing. This finding signals that experiences of rejection play a role in constraining people’s housing choices. 
• The survey findings suggest that discrimination, as part of tenant selection, contributes to housing precarity and inequalities in access to rental housing. Therefore, this research points to an urgent need to address housing discrimination, especially in the context of high levels of residential mobility among renters and intense competition for rental properties.

text: “Landlords wouldn’t give my application a second look.” Discrimination exacerbates inequalities in access to private rental housing This report and the key insights are based on findings from a housing survey that was conducted with 800 residents in neighbourhoods in Auckland, Hamilton and Christchurch. 
• Perceptions of unfairness in Aotearoa’s housing sector are widespread. Renters, Māori, younger people and low-income groups as well as residents in neighbourhoods with high levels of housing deprivation are most likely to think that people are treated unfairly when trying to rent or buy a home in Aotearoa. 
• Nearly one in three respondents reported having experienced discrimination when trying to rent or buy a home in Aotearoa. Renters, Māori, younger people and low-income groups as well as residents in neighbourhoods with high levels of housing deprivation are most likely to report experiences of discrimination. 
• Advantage and disadvantage in securing a home are determined by a combination of interlocking factors, including income and employment status, age, family status, and race/ethnicity or skin colour. These patterns suggest widespread experiences of potentially unlawful housing discrimination. 
• People strategically try to avoid and mitigate discrimination. Expectations of being discriminated against and of being advantaged influence where and how home seekers search for housing. This finding signals that experiences of rejection play a role in constraining people’s housing choices. 
• The survey findings suggest that discrimination, as part of tenant selection, contributes to housing precarity and inequalities in access to rental housing. Therefore, this research points to an urgent need to address housing discrimination, especially in the context of high levels of residential mobility among renters and intense competition for rental properties.

year: 2024-08