H2O: An Autonomic, Resource-Aware Distributed Database System

This paper presents the design of an autonomic, resource-aware distributed database which enables data to be backed up and shared without complex manual administration. The database, H2O, is designed to make use of unused resources on workstation machines. Creating and maintaining highly-available, replicated database systems can be difficult for untrained users, and costly for IT departments. H2O reduces the need for manual administration by autonomically replicating data and load-balancing across machines in an enterprise. Provisioning hardware to run a database system can be unnecessarily costly as most organizations already possess large quantities of idle resources in workstation machines. H2O is designed to utilize this unused capacity by using resource availability information to place data and plan queries over workstation machines that are already being used for other tasks. This paper discusses the requirements for such a system and presents the design and implementation of H2O.Comment: Presented at SICSA PhD Conference 2010 (http://www.sicsaconf.org/

An Approach to Ad hoc Cloud Computing

We consider how underused computing resources within an enterprise may be harnessed to improve utilization and create an elastic computing infrastructure. Most current cloud provision involves a data center model, in which clusters of machines are dedicated to running cloud infrastructure software. We propose an additional model, the ad hoc cloud, in which infrastructure software is distributed over resources harvested from machines already in existence within an enterprise. In contrast to the data center cloud model, resource levels are not established a priori, nor are resources dedicated exclusively to the cloud while in use. A participating machine is not dedicated to the cloud, but has some other primary purpose such as running interactive processes for a particular user. We outline the major implementation challenges and one approach to tackling them

Study of the relationship between virus and host cell

The author began work in the virus field at the University of Edinburgh in 1946 in collaboration with Dr. C. E. van Rooyen. Interest was first centred in the pro - blem of obtaining fowl pox virus in a highly purified state and subjecting it to chemical and physical analysis. After some months of work it became apparent that the most interesting and fundamental problem in virology was the process of viral multiplication, that this was a study in biochemical dynamics and that the collection of analytical data for another purified virus was not likely o contribute much to its solution. At that time the view that virus multiplication was similar to that of bacteria was still widely held, but it seemed to the author that this hypothesis was open to doubt.While most bacteria have the complete metabolic apparatus which will enable them to grow in a liquid medium often remarkably simple in composition, and can adapt themselves to grow under a variety of conditions, no virus has yet been found to grow in the absence of its host cell. Since virus particles apparently have none of the metabolic functions required for growth, it followed that during their intracellular growth the host must play more than a purely passive role. The idea was then conceived that the virus attached itself to the host and from that time on directed the course of intracellular reactions. Under this influence the cell was supposed to cease its synthesis of cell constituents and instead synthesize new virus. The onus for virus production was thereby placed entirely on the cell and the invading particle took little active part after initiating the infection. While this was a considerable departure from prevailing views, there were already indications in the literature that such a mechanism had been considered by others (Green, Science, 82, 443, 1935; Laidlaw, Virus Diseases and Viruses, Cambridge Univ. Press, 1938). It is now known that a number of research groups in Europe and North America were working with a similar hypothesis in mind at the end of 1946 andlas will be shown later, this hypothesis in a more elaborate form #has now gained wide acceptance.Work was begun by the author in 1947 at the University of Toronto to determine whether it might be possible to label an animal or bacterial virus with P32. If this proved successful, it was proposed firstly to study the behaviour of the labelled virus particle on infection of its host and secondly to investigate intracellular virus synthesis utilizing isotope techniques.The main technical requirements in such a study were (a) a virus host system which was relatively simple and subject to experimental control; (b) a virus that could be grown readily in high yield, was easily purified from host constituents and whose chemical and physical properties had already been worked out in some detail; and (c) a virus that contained one per cent or more of phosphorus so that it would take up sufficient P32 during growth to make the labelled virus a useful experimental tool. Two systems satisfied these requirements, (1) influenza virus adapted to growth in the embryonated egg and (2) the seven T bacteriophages active on Escherichia coli. Work was therefore initiated on both systems.It was found that influenza virus could be labelled with P³² by growing it in the allantoic membrane of the embryonated egg with inorganic p³² placed in the allantoic fluid. Control experiments and chemical analysis indicated that the label was incorporated into the virus during its growth, and there was no direct exchange of P³² between virus and inorganic phosphate. Chemical analyses of the phosphorus constituents in allantoic membrane were also carried out in preparation for experiments on membrane infected with labelled virus.The remainder of this thesis is concerned with research on the set of seven bacteriophages, active on the host E. coli, commonly referred to as the T group. When the present work was begun more exact knowledge had been accumulated about the biological properties of bacteriophages than any other type of virus. Bacteriophages are relatively easy to handle and had attracted the attention of a number of outstanding workers among whom d'Herelle, Burnet, Craigie and Delbruck were pre-eminent.Each of the T phages can mutate during growth in a number of known ways and probably a variety of unknown ways. The host bacteria also mutate and it is relatively easy to obtain variants of the original strain resistant to one or more of the seven phages. Some of the mutants of both phage and cells are extraordinarily useful as experimental tools in biochemical experiments and the problems involved in the mutation of the phages provide the main approach to the genetic side of the problem.As described in the present work, it was found that T2 bacteriophage could readily be labelled with P²³ and that at least 95% of the isotope was contained in the desoxyribonucleic acid moiety of the virus. when the cell was infected with the labelled virus there was a rapid and extensive breakdown of the particle although up to 350 of the P²³ appeared in the viral progeny. The extent of breakdown and the contribution of parental P²³ to progeny varied considerably with experimental conditions and were studied in some detail. In a later section the significance of these findings is discussed in the light of recent knowledge on virus multiplication

Study in epidemiology: illustrated by a diphtheria epidemic

The consideration of Epidemic disease here set out, while illustrated by the study of a Diphtheria Epidemic, represents rather the conclusions arrived at after some twenty years experience of disease in general gained in the practice of Medicine and Surgery, amplified by two years recently devoted to the study of Preventive Medicine and Bacteriology in particular. Little of originality is claimed ; but the exceptional advantage of being able to discuss an epidemic from personal investigation thereof, from the clinical and epidemiological at the same time as from the Bacteriological standpoint is undoubted. Personal experience would stand for little, unless it had been aided by the study of the recent and current literature on the subject of Diphtheria and Epidemics in general. Contributions to the various Medical Journals, `Public Health,' Journal of Hygiene, and different publications and text books have all been taken advantage of ; and amongst others contributing to these may be mentioned the names of Loeffler, Newsholme, Newman, Theobald Smith, Cobbett, Graham Smith, Delépine, Woodhead. I may add that I owe much to Professor Delépine of Manchester, under whom I spent various periods of study from 1908 to 1910 ; for no one can come in contact with him without being infected with his enthusiasm in the cause of Preventive Medicine and trying to emulate in some degree his extraordinary precision and thoroughness and attempting to adopt his breadth of outlook. The personal friendship as well as continuous help and suggestion of Dr. Buckley, Medical Officer of Health for Crewe, greatly assisted my work at Crewe

Towards Adaptable and Adaptive Policy-Free Middleware

We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

Incremental validation of policy-based systems

Policy-based systems are gaining popularity as a way to manage applications with dynamic behaviour. These systems have policies specifying the desired behaviour, entered into the system by either end-users or system administrators. In order to assure that the policies don't violate any stipulated properties of the system or conflict with one another, the policies must be validated. This validation process can take a very large amount of time as the system's policy base grows. This thesis suggests an incremental validation method, whereby a system which has been determined to be consistent can be validated when a new rule is added to the system. "Trigger chaining" is a concept introduced in this thesis that examines which policies are triggered by the firing of a particular policy. This concept leads to new kinds of conflicts. An algorithm is suggested for incremental detection of such conflicts and is shown to operate in linear time, as opposed to complete revalidation which has quadratic complexity. Trigger chaining also leads to the detection of cyclic conflicts which are briefly discussed. Decision tables are suggested as a suitable format for the internal representation of policies. This format provides a method of checking a policy set for completeness and could help in checking for conflicts. Also decision tables are shown to be a natural format for storing policies. It is also known how to convert decision tables into executable rules, making the transition from decision table-based policies to rule engine policies a simple on