title: Investigating the memory requirements for publish/subscribe filtering algorithms

authors: Bittner, Sven

subjects: computer science

abstract: Various filtering algorithms for publish/subscribe systems have been proposed. One distinguishing characteristic is their internal representation of Boolean subscriptions: They either require conversions to disjunctive normal forms (canonical approaches) or are directly exploited in event filtering (non-canonical approaches).
In this paper, we present a detailed analysis and comparison of the memory requirements of canonical and non-canonical filtering algorithms. This includes a theoretical analysis of space usages as well as a verification of our theoretical results by an evaluation of a practical implementation. This practical analysis also considers time (filter) efficiency, which is the other important quality measure of filtering algorithms. By correlating the results of space and time efficiency, we conclude when to use non-canonical and canonical approaches.

text: Investigating the memory requirements for publish/subscribe filtering algorithms Various filtering algorithms for publish/subscribe systems have been proposed. One distinguishing characteristic is their internal representation of Boolean subscriptions: They either require conversions to disjunctive normal forms (canonical approaches) or are directly exploited in event filtering (non-canonical approaches).
In this paper, we present a detailed analysis and comparison of the memory requirements of canonical and non-canonical filtering algorithms. This includes a theoretical analysis of space usages as well as a verification of our theoretical results by an evaluation of a practical implementation. This practical analysis also considers time (filter) efficiency, which is the other important quality measure of filtering algorithms. By correlating the results of space and time efficiency, we conclude when to use non-canonical and canonical approaches.

year: 2005-01-01

title: In-kernel passive measurement of the performance impact of hidden terminals in 802.11 wireless networks

authors: Raynel, Scott McKenzie

subjects: computer science

abstract: The negative performance impact of the presence of hidden terminals in wireless networks has been well know for decades. Despite much research in the area, many deployed networks continue to suffer a performance penalty because of hidden terminals. Ad hoc wireless networks are particularly susceptible to hidden terminal collisions because there are fewer opportunities to plan the network in a way that avoids or reduces the number of hidden terminals. Measuring the presence of hidden terminals and the impact they are having on performance is difficult, especially in a network of many nodes. Without such measurements, the users and operators of wireless networks can not tell if performance problems are caused by hidden terminals or some other problem. We introduce new methodology that can detect the presence of hidden terminals and estimate the performance impact they are causing. The methodology requires no additional hardware and is suitable for wide scale deployment and long term operation. The approach is based on in-kernel instrumentation of the wireless network stack. The design, implementation, and testing of the approach are covered. Results from in-lab testing and the measurement of a live commercial 802.11 network are also presented, including a case study where performance was significantly improved.

text: In-kernel passive measurement of the performance impact of hidden terminals in 802.11 wireless networks The negative performance impact of the presence of hidden terminals in wireless networks has been well know for decades. Despite much research in the area, many deployed networks continue to suffer a performance penalty because of hidden terminals. Ad hoc wireless networks are particularly susceptible to hidden terminal collisions because there are fewer opportunities to plan the network in a way that avoids or reduces the number of hidden terminals. Measuring the presence of hidden terminals and the impact they are having on performance is difficult, especially in a network of many nodes. Without such measurements, the users and operators of wireless networks can not tell if performance problems are caused by hidden terminals or some other problem. We introduce new methodology that can detect the presence of hidden terminals and estimate the performance impact they are causing. The methodology requires no additional hardware and is suitable for wide scale deployment and long term operation. The approach is based on in-kernel instrumentation of the wireless network stack. The design, implementation, and testing of the approach are covered. Results from in-lab testing and the measurement of a live commercial 802.11 network are also presented, including a case study where performance was significantly improved.

year: 2011

title: !!!FR33D0M 0FF SP33CH!!!

authors: Smith, Hugh Lyal

subjects: Poetry

abstract: My title is “FR33D0M 0FF SP33CH”, a play on the saying “freedom of speech”. I write with the intent of voicing tough subjects that others haven’t or don’t, and often exposing things that I wouldn’t tell or share personally. “FR33D0M 0FF SP33CH” consists of 37 poems, 2 hooks and a chorus in this complete album. My earliest piece can date back to 2020 with the latest pieces being written in 2021. They express different visions of day-to-day life through points of view and alternating voices and perspectives. The topics range from anything like seeing a face in the smudge on a wall, to things like love, street styles and why I can’t sleep at night. They are to be read left to right, top to bottom -- but feel free to read them as you see fit, because it’s art after all and what you see is what you see. Those labelled “Mirrored” have been turned upside down to allow reading from either end and show the extent of form and variety my pieces can take. Some things may be explicit or hard to read, but I assure you that they are just certain views from different angles that I believe need to be shared. There is a strong political/cultural component to my mahi, a tough vocal attack on elements of society I believe are flawed and unjust, and an exposure of the addictions and abuses that colonial history and racial inequality lead to – but there’s also an intense celebration of the power of the Māori voice that remains, its beat and pride and resilience and ancestry, joined by a rich musical joy in the songs of the street I grew up in, their rhythms and rap, energy and power. It has taken me a long time to reach this level of writing in terms of technique, rhythm and content. I want the reader to see things through my shades and feel what it feels like to be me with an understanding of why I am and where I come from. To understand that, No, I don’t know everything, and I don’t expect anyone else to. But, Yes, this is what I saw, felt and how I interpreted it. So there it is and this is me, the bro Hugh. A lit ūrikā descendant of Ngāti Kuri, Ngāti Rēhia, Te Rārawa, Te Aupōuri and Ngāpuhi. Bred in the streets I-roam and made home. A dreamer of the future. Last but not least, your son, your brother, your bro and he who wrote the killer book that you are about to read. Churrr!!!

text: !!!FR33D0M 0FF SP33CH!!! My title is “FR33D0M 0FF SP33CH”, a play on the saying “freedom of speech”. I write with the intent of voicing tough subjects that others haven’t or don’t, and often exposing things that I wouldn’t tell or share personally. “FR33D0M 0FF SP33CH” consists of 37 poems, 2 hooks and a chorus in this complete album. My earliest piece can date back to 2020 with the latest pieces being written in 2021. They express different visions of day-to-day life through points of view and alternating voices and perspectives. The topics range from anything like seeing a face in the smudge on a wall, to things like love, street styles and why I can’t sleep at night. They are to be read left to right, top to bottom -- but feel free to read them as you see fit, because it’s art after all and what you see is what you see. Those labelled “Mirrored” have been turned upside down to allow reading from either end and show the extent of form and variety my pieces can take. Some things may be explicit or hard to read, but I assure you that they are just certain views from different angles that I believe need to be shared. There is a strong political/cultural component to my mahi, a tough vocal attack on elements of society I believe are flawed and unjust, and an exposure of the addictions and abuses that colonial history and racial inequality lead to – but there’s also an intense celebration of the power of the Māori voice that remains, its beat and pride and resilience and ancestry, joined by a rich musical joy in the songs of the street I grew up in, their rhythms and rap, energy and power. It has taken me a long time to reach this level of writing in terms of technique, rhythm and content. I want the reader to see things through my shades and feel what it feels like to be me with an understanding of why I am and where I come from. To understand that, No, I don’t know everything, and I don’t expect anyone else to. But, Yes, this is what I saw, felt and how I interpreted it. So there it is and this is me, the bro Hugh. A lit ūrikā descendant of Ngāti Kuri, Ngāti Rēhia, Te Rārawa, Te Aupōuri and Ngāpuhi. Bred in the streets I-roam and made home. A dreamer of the future. Last but not least, your son, your brother, your bro and he who wrote the killer book that you are about to read. Churrr!!!

year: 2021