title: General Boolean expressions in publish-subscribe systems

authors: Bittner, Sven

subjects: Boolean expressions

abstract: The increasing amount of electronically available information in society today is undeniable. Examples include the numbers of general web pages, scientific publications, and items in online auctions. From a user's perspective, this trend will lead to information overflow. Moreover, information publishers are compromised by this situation, as users have greater difficulty in identifying useful information.

Publish-subscribe systems can be applied to cope with the reality of information overflow. In these systems, users specify their information interests as subscriptions and, subsequently, only matching information (event messages) is delivered; uninteresting information is filtered out before reaching users. In this dissertation, we consider content-based publish-subscribe systems, a sophisticated example of these systems. They perform the information-filtering task based on the content of provided information. In order to deal with high numbers of subscriptions and frequencies of event messages, publish-subscribe systems are realized as distributed systems. Advertisements - publisher specifications of potential future event messages - are optionally applied in these systems to reduce the internal distribution of subscriptions.

Existing work on content-based publish-subscribe concepts mainly focuses on subscriptions and advertisements as pure conjunctive expressions. Therefore, subscriptions or advertisements using operators other than conjunction need to be canonically converted to disjunctive normal form by these systems. Each conjunctive component is then treated as individual subscription or advertisement. Unfortunately, the size of converted expressions is exponential in the worst case.

In this dissertation, we show that the direct support of general Boolean subscriptions and advertisements improves the time and space efficiency of general-purpose content-based publish-subscribe systems. For this purpose, we develop suitable approaches for the filtering and routing of general Boolean expressions in these systems. Our approaches represent solutions to exactly those components of content-based publish-subscribe systems that currently restrict subscriptions and advertisements to conjunctive expressions.

On the subscription side, we present an effective generic filtering algorithm, and a novel approach to optimize event routing tables, which we call subscription pruning. To support advertisements, we show how to calculate the overlap between subscriptions and advertisements, and introduce the first designated subscription routing optimization, which we refer to as advertisement pruning. We integrate these approaches into our prototype BoP (BOolean Publish-subscribe) which allows for the full support of general Boolean expressions in its filtering and routing components.

In the evaluation part of this dissertation, we empirically analyze our prototypical implementation BoP and compare its algorithms to existing conjunctive solutions. We firstly show that our general-purpose Boolean filtering algorithm is more space- and time-efficient than a general-purpose conjunctive filtering algorithm. Secondly, we illustrate the effectiveness of the subscription pruning routing optimization and compare it to the existing covering optimization approach. Finally, we demonstrate the optimization effect of advertisement pruning while maintaining the existing overlapping relationships in the system.

text: General Boolean expressions in publish-subscribe systems The increasing amount of electronically available information in society today is undeniable. Examples include the numbers of general web pages, scientific publications, and items in online auctions. From a user's perspective, this trend will lead to information overflow. Moreover, information publishers are compromised by this situation, as users have greater difficulty in identifying useful information.

Publish-subscribe systems can be applied to cope with the reality of information overflow. In these systems, users specify their information interests as subscriptions and, subsequently, only matching information (event messages) is delivered; uninteresting information is filtered out before reaching users. In this dissertation, we consider content-based publish-subscribe systems, a sophisticated example of these systems. They perform the information-filtering task based on the content of provided information. In order to deal with high numbers of subscriptions and frequencies of event messages, publish-subscribe systems are realized as distributed systems. Advertisements - publisher specifications of potential future event messages - are optionally applied in these systems to reduce the internal distribution of subscriptions.

Existing work on content-based publish-subscribe concepts mainly focuses on subscriptions and advertisements as pure conjunctive expressions. Therefore, subscriptions or advertisements using operators other than conjunction need to be canonically converted to disjunctive normal form by these systems. Each conjunctive component is then treated as individual subscription or advertisement. Unfortunately, the size of converted expressions is exponential in the worst case.

In this dissertation, we show that the direct support of general Boolean subscriptions and advertisements improves the time and space efficiency of general-purpose content-based publish-subscribe systems. For this purpose, we develop suitable approaches for the filtering and routing of general Boolean expressions in these systems. Our approaches represent solutions to exactly those components of content-based publish-subscribe systems that currently restrict subscriptions and advertisements to conjunctive expressions.

On the subscription side, we present an effective generic filtering algorithm, and a novel approach to optimize event routing tables, which we call subscription pruning. To support advertisements, we show how to calculate the overlap between subscriptions and advertisements, and introduce the first designated subscription routing optimization, which we refer to as advertisement pruning. We integrate these approaches into our prototype BoP (BOolean Publish-subscribe) which allows for the full support of general Boolean expressions in its filtering and routing components.

In the evaluation part of this dissertation, we empirically analyze our prototypical implementation BoP and compare its algorithms to existing conjunctive solutions. We firstly show that our general-purpose Boolean filtering algorithm is more space- and time-efficient than a general-purpose conjunctive filtering algorithm. Secondly, we illustrate the effectiveness of the subscription pruning routing optimization and compare it to the existing covering optimization approach. Finally, we demonstrate the optimization effect of advertisement pruning while maintaining the existing overlapping relationships in the system.

year: 2008

title: Overseas Trained Teachers' Experiences of Professional Socialisation in New Zealand

authors: Butcher, Jane

subjects: overseas trained teacher

abstract: This research traces the early experiences of overseas trained teachers (OTTs) recommencing their careers in urban secondary schools in New Zealand. The teachers’ professional lives during the first three terms of their employment are explored through their experiences. Participants’ share their perceptions and interpretations of the new situations, processes and events they encounter in their schools and beyond. 

The purpose of this research is to discover how immigrant teachers experience the systems and processes required to become members of their professional community. Aspects of participants’ experiences of national systems for immigration, qualification recognition, teacher registration, and salary assessment are discussed. School systems for teacher induction and professional learning are also critiqued.

The research contributes to the debate about the role and integration of OTTs in New Zealand schools. It will be of interest to national agencies, school principals and those with responsibility for teacher supply, teacher education and the provision of ongoing professional learning for teachers. The research also contributes to greater understanding of the lived experiences of migrant professionals in New Zealand. 

An interpretive research paradigm has been followed and a hermeneutic phenomenological methodological approach chosen to capture the lived experiences of the participants through their journeys towards professional socialisation. The research is guided by the philosophical thinking of Heidegger, Gadamer and van Manen. 

Ten participants shared their lived experiences through reports and anecdotes of events, relationships, emotions, and subjectivities as they occurred within the structures, institutions, and policies of their new environments. The findings revealed OTTs’ negative experiences with multilayered systems as they strove to establish their private and professional identities. 

The findings have uncovered systemic failure by agencies and schools to provide the necessary formal induction and ongoing assistance to meet the perceived needs of OTTs and facilitate their transition into New Zealand classrooms. It is shown that schools and their OTTs rely heavily on informal arrangements between colleagues to overcome knowledge gaps and communicate information. The progress of immigrant teachers towards professional socialisation is affected by their positioning and that of their schools. It is also shown to be aided by involvement with extra-curricula activities and the resumption of familiar hobbies, sports and interests. 

The research raises concern for the sustenance of OTTs in the New Zealand teaching community. It indicates that there is need for a wider study, and the follow up of teachers who immigrate to New Zealand to inform the systems and procedures for their professional socialisation.

text: Overseas Trained Teachers' Experiences of Professional Socialisation in New Zealand This research traces the early experiences of overseas trained teachers (OTTs) recommencing their careers in urban secondary schools in New Zealand. The teachers’ professional lives during the first three terms of their employment are explored through their experiences. Participants’ share their perceptions and interpretations of the new situations, processes and events they encounter in their schools and beyond. 

The purpose of this research is to discover how immigrant teachers experience the systems and processes required to become members of their professional community. Aspects of participants’ experiences of national systems for immigration, qualification recognition, teacher registration, and salary assessment are discussed. School systems for teacher induction and professional learning are also critiqued.

The research contributes to the debate about the role and integration of OTTs in New Zealand schools. It will be of interest to national agencies, school principals and those with responsibility for teacher supply, teacher education and the provision of ongoing professional learning for teachers. The research also contributes to greater understanding of the lived experiences of migrant professionals in New Zealand. 

An interpretive research paradigm has been followed and a hermeneutic phenomenological methodological approach chosen to capture the lived experiences of the participants through their journeys towards professional socialisation. The research is guided by the philosophical thinking of Heidegger, Gadamer and van Manen. 

Ten participants shared their lived experiences through reports and anecdotes of events, relationships, emotions, and subjectivities as they occurred within the structures, institutions, and policies of their new environments. The findings revealed OTTs’ negative experiences with multilayered systems as they strove to establish their private and professional identities. 

The findings have uncovered systemic failure by agencies and schools to provide the necessary formal induction and ongoing assistance to meet the perceived needs of OTTs and facilitate their transition into New Zealand classrooms. It is shown that schools and their OTTs rely heavily on informal arrangements between colleagues to overcome knowledge gaps and communicate information. The progress of immigrant teachers towards professional socialisation is affected by their positioning and that of their schools. It is also shown to be aided by involvement with extra-curricula activities and the resumption of familiar hobbies, sports and interests. 

The research raises concern for the sustenance of OTTs in the New Zealand teaching community. It indicates that there is need for a wider study, and the follow up of teachers who immigrate to New Zealand to inform the systems and procedures for their professional socialisation.

year: 2012

title: Te Mata Ono-The six faces of Māori broadcasting

authors: Kaire-Melbourne, Kimiora

subjects: Māori broadcasting

abstract: Māori have always been involved in media communication and from a traditional viewpoint karanga, whaikōrero, taonga pūoro, haka, waiata and mōteatea are all mediums used to share messages across a mass audience. Since the arrival of European settlers, we have seen Māori content disseminated through platforms such as newspaper, radio, and more recently via the medium of television. This particular study is concerned with the way that Māori are represented and information is shared via indigenous broadcaster, Māori Television. Using a theoretical model made up of six key components, this thesis asserts that Te Mata Ono could not only help to improve the production of Māori content but also reshape and modify the medium of television itself, to become more culturally appropriate. Ultimately, this model could guide Māori Television, outlining a Māori specific approach to broadcasting. This study is one part of a two-part study. Due to the limitations of a four-paper masters thesis, I will only be examining three elements of Te Mata Ono, which are Mata Māori, Mata ō-tua and Mata Pākehā. Another thesis that was conducted simultaneously by Te Aorere Pewhairangi explores the remaining three elements of the same model, Mata Iwi, Mata Ako and Mata Tikanga. Te Mata Ono could be applied to Māori Television, making a positive contribution to the future development of Māori broadcasting.

text: Te Mata Ono-The six faces of Māori broadcasting Māori have always been involved in media communication and from a traditional viewpoint karanga, whaikōrero, taonga pūoro, haka, waiata and mōteatea are all mediums used to share messages across a mass audience. Since the arrival of European settlers, we have seen Māori content disseminated through platforms such as newspaper, radio, and more recently via the medium of television. This particular study is concerned with the way that Māori are represented and information is shared via indigenous broadcaster, Māori Television. Using a theoretical model made up of six key components, this thesis asserts that Te Mata Ono could not only help to improve the production of Māori content but also reshape and modify the medium of television itself, to become more culturally appropriate. Ultimately, this model could guide Māori Television, outlining a Māori specific approach to broadcasting. This study is one part of a two-part study. Due to the limitations of a four-paper masters thesis, I will only be examining three elements of Te Mata Ono, which are Mata Māori, Mata ō-tua and Mata Pākehā. Another thesis that was conducted simultaneously by Te Aorere Pewhairangi explores the remaining three elements of the same model, Mata Iwi, Mata Ako and Mata Tikanga. Te Mata Ono could be applied to Māori Television, making a positive contribution to the future development of Māori broadcasting.

year: 2019