Eventual election of multiple leaders for solving consensus in anonymous systems

In classical distributed systems, each process has a unique identity. Today, new distributed systems have emerged where a unique identity is not always possible to be assigned to each process. For example, in many sensor networks a unique identity is not possible to be included in each device due to its small storage capacity, reduced computational power, or the huge number of devices to be identified. In these cases, we have to work with anonymous distributed systems where processes cannot be identified. Consensus cannot be solved in classical and anonymous asynchronous distributed systems where processes can crash. To bypass this impossibility result, failure detectors are added to these systems. It is known that ? is the weakest failure detector class for solving consensus in classical asynchronous systems when amajority of processes never crashes. Although A? was introduced as an anonymous version of ?, to find the weakest failure detector in anonymous systems to solve consensus when amajority of processes never crashes is nowadays an open question. Furthermore, A? has the important drawback that it is not implementable. Very recently, A? has been introduced as a counterpart of ? for anonymous systems. In this paper, we show that the A? failure detector class is strictly weaker than A? (i.e., A? provides less information about process crashes than A?). We also present in this paper the first implementation of A? (hence, we also show that A? is implementable), and, finally, we include the first implementation of consensus in anonymous asynchronous systems augmented with A? and where a majority of processes does not crash

Reliable broadcast in anonymous distributed systems with fair lossy channels

Reliable Broadcast (RB) is a basic abstraction in distributed systems, because it allows processes to communicate consistently and reliably to each other. It guarantees that all correct process reliable deliver the same set of messages. This abstraction has been extensively investigated in distributed systems where all processes have different identifiers, and the communication channels are reliable. However, more and more anonymous systems appear due to the motivation of privacy. It is significant to extend RB into anonymous system model where each process has no identifier. In another hand, the requirement of reliable communication channels is not always satisfied in real systems. Hence, this paper is aimed to study RB abstraction in anonymous distributed systems with fair lossy communication channels. In distributed systems, symmetry always mean that two systems should be considered symmetric if they behave identically, and two components of a system should be considered symmetric if they are indistinguishable. Hence, the anonymous distributed systems is symmetry. The design difficulty of RB algorithm lies in how to break the symmetry of the system. In this paper, we propose to use a random function to break it. Firstly, a non-quiescent RB algorithm tolerating an arbitrary number of crashed processes is given. Then, we introduce an anonymous perfect failure detector AP?. Finally, we propose an extended and quiescent RB algorithm using AP?

Tempo- Apr. 17, 1945

https://neiudc.neiu.edu/tempo/1011/thumbnail.jp

Summary of research on methods and devices for teaching the vocabulary of English as a foreign language

Thesis (Ed.M.)--Boston Universit

The Role of the Unit Leader, Individually Guided Education

This field study defines the role of a Unit Leader in a school using Individually Guided Education. Specifically, it defines the role of a unit leader at Roach School in Decatur, Illinois. Individually Guided Education is a new form of elementary education. It uses multiunit organization and instructional programming for individual students. It uses an Instructional Improvement Committee made up of unit or team leaders and the principal. These persons coordinate the curriculum within the school. The writer defined each of these areas - Individually Guided Education, Unit Leader, and the Instructional Improvement Committee in two ways. One definition looked at the terms as they are seen by those who authored the program. The other definition examined how they functioned at Roach School in Decatur, Illinois. Several major differences were noted: In most areas using Individually Guided Education there is more than one school in each district participating. In Decatur, there was only one at the time the study was done. Unit Leaders in most systems using Individually Guided Education are given monetary compensation for their work. At Roach School there was no compensation given. Unit Leaders in most systems using Individually Guided Education are given released time to perform their duties. At Roach School, this was not the case. In most schools using Individually Guided Education there were aides hired for each team. At Roach School, the majority of our aides are there due to the Special Education classrooms. Unit Leaders meet certain qualifications and were then appointed by the principal in most Individually Guided Education schools. This was not the case at Roach School. The unit leaders were elected by the unit members. There are several conclusions to be drawn. Individually Guided Education at Roach School could be administered more efficiently. Persons who are paid to do a job and given the time to do it are more apt to be efficient and do their best. Persons who are asked to give up their own time for no compensation are not apt to do their best. Furthermore, many do not want any part of that job. The qualifications are important. The job requires someone who can lead people as well as have ideas to improve the curriculum. So, the one who is just willing to say, “I’ll do the job for a year.” is not always the one who will be the best for the school. Also included in the field study, are minutes of the Instructional Improvement Committee throughout the year. Related materials, such as evaluations, printed materials, and budgets are found in the appendixes

Lexical database enrichment through semi-automated morphological analysis

Derivational morphology proposes meaningful connections between words and is largely unrepresented in lexical databases. This thesis presents a project to enrich a lexical database with morphological links and to evaluate their contribution to disambiguation. A lexical database with sense distinctions was required. WordNet was chosen because of its free availability and widespread use. Its suitability was assessed through critical evaluation with respect to specifications and criticisms, using a transparent, extensible model. The identification of serious shortcomings suggested a portable enrichment methodology, applicable to alternative resources. Although 40% of the most frequent words are prepositions, they have been largely ignored by computational linguists, so addition of prepositions was also required. The preferred approach to morphological enrichment was to infer relations from phenomena discovered algorithmically. Both existing databases and existing algorithms can capture regular morphological relations, but cannot capture exceptions correctly; neither of them provide any semantic information. Some morphological analysis algorithms are subject to the fallacy that morphological analysis can be performed simply by segmentation. Morphological rules, grounded in observation and etymology, govern associations between and attachment of suffixes and contribute to defining the meaning of morphological relationships. Specifying character substitutions circumvents the segmentation fallacy. Morphological rules are prone to undergeneration, minimised through a variable lexical validity requirement, and overgeneration, minimised by rule reformulation and restricting monosyllabic output. Rules take into account the morphology of ancestor languages through co-occurrences of morphological patterns. Multiple rules applicable to an input suffix need their precedence established. The resistance of prefixations to segmentation has been addressed by identifying linking vowel exceptions and irregular prefixes. The automatic affix discovery algorithm applies heuristics to identify meaningful affixes and is combined with morphological rules into a hybrid model, fed only with empirical data, collected without supervision. Further algorithms apply the rules optimally to automatically pre-identified suffixes and break words into their component morphemes. To handle exceptions, stoplists were created in response to initial errors and fed back into the model through iterative development, leading to 100% precision, contestable only on lexicographic criteria. Stoplist length is minimised by special treatment of monosyllables and reformulation of rules. 96% of words and phrases are analysed. 218,802 directed derivational links have been encoded in the lexicon rather than the wordnet component of the model because the lexicon provides the optimal clustering of word senses. Both links and analyser are portable to an alternative lexicon. The evaluation uses the extended gloss overlaps disambiguation algorithm. The enriched model outperformed WordNet in terms of recall without loss of precision. Failure of all experiments to outperform disambiguation by frequency reflects on WordNet sense distinctions

An analysis of the literature on motivation in typewriting.

Thesis (Ed.M.)--Boston Universit