The approach used in this document is to create an assisting table as a bridge between the base table and view, on which only projection of non-identifying attributes is performed. This makes it possibly to distinguish individual records to enable log recovery methods to keep the assisting table consistent with the base table. The assisting table can then be used to create and maintain the view without blocking the base table.

MapReduce is a programming model for distributed processing, originally designed by Google Inc. It is designed to simplify the implementation and deployment of distributed programs. Vespa Document Store (VDS) is a distributed document storage solution developed by Yahoo! Technologies Norway. VDS does not currently have any feature allowing distributed aggregation of data. Therefore, a prototype of the MapReduce distributed programming model was previously developed. However, the implementation requires manual tuning of several parameters before each deployment. The goal of this thesis is to allow as many as possible of these parameters to be either automatically configured or set to universally suitable defaults. We have created a working MapReduce implementation based on previous work, and a framework for monitoring of VDS nodes. Various VDS features have been documented in detail, this documentation has been used to analyse how the performance of these features may be improved. We have also performed various experiments to validate the analysis and gain additional insight. Numerous configuration options for either VDS in general or the MapReduce implementation have been considered, and recommended settings have been proposed. The propositions are either in the form of default values or algorithms for computing the most suitable setting. Finally, we provide a list of suggested further work, with suggestions for both general VDS improvements and MapReduce-specific research.

http://odc.opentheweb.org/

MMOGs (Massively Multiplayer Online Games) are today a multi-bilion dollar industry where typically thousands of players interact in a virtual world. Two of the main complaints of the MMOG community are the lack of interaction with the virtual universe, and the repetitive gameplay patterns. Introducing a virtual alimentary chain for the targets would allow for a much more exciting experience since the genetic evolution of the opponents would make each fight more unique, and collaboration among player community would be necessary to keep a sustainable balance in the virtual world. As these kind of games are designed for many thousands of players in real-time, a lot of compute power will be needed to simulate the genetic evolution. Parallel computing can greatly improve the performance, assuming the software is properly designed with parallelizations in mind. A couple of different schemes will be considered. Trying to fetch the ecology studies, a prototype architecture is presented here. A non-linear genotype-phenotype transformation mechanism (also called morphogenesis) has been designed with the purpose of obtaining Lotka-Volterra equations result. These research will lead to discussions and conclusion, hopefully guiding further development in this area.

This report is for my research of Collaboration Instance Manager of UbiCollab project. UbiCollab want to be the platform for ubiquitous collaborative active. UbiCollab project aims to develop a distributed collaborative platform which makes people in distributed space ubiquitous collaborate with friends and colleagues. Collaboration instance manager (CIM) is a core component of the UbiCollab platform, which manage such collaborative activities. My research topics of CIM include in the P2P network development by using JXME, the data synchronization through this P2P network and how to manage these synchronized date by using a local file system. The result of my research is a CIM system, which deployed as OSGI bundle. User can use that do some collaborative active. This CIM system manage the service level of data synchronization, other modules and applications can use that to handle data synchronization between each other without know the details of how to implement it. For that purpose I first reviewed the related theories of distributed systems, ubiquitous systems, mobile systems and CSCW. After that review I researched on some alternatives for developing such system and choose the candidate technologies for my prototype. Secondly I analyzed the requirements of UbiCollab and designed the prototype. Based on that design, I implemented and tested that CIM system based on agreed common scenarios and developed a simple GUI for show the utility. Finally, I evaluate the system by analysis system requirements and scenario criteria.

This report aims to describe and improve a system recovery process in large-scale storage systems. Inevitable, a recovery process results in the system being loaded with internal replication of data, and will extensively utilize several storage nodes. Such internal load can be categorized and generalized into a maintenance workload class. Obviously, a storage system will have external clients which also introduce load into the system. This can be users altering their data, uploading new content, etc. Load generated by clients can be generalized into a production workload class. When both workload classes are actively present in a system, i.e. the system is recovering while users are simultaneously accessing their data, there will be a competition of system resources between the different workload classes. The storage must ensure Quality of Service (QoS) for each workload class so that both are guaranteed system resources. We have created Dynamic Tree with Observed Metrics (DTOM), an algorithm designed to gracefully throttle resources between multiple different workload classes. DTOM can be used to enforce and ensure QoS for the variety of workloads in a system. Experimental results demonstrate that DTOM outperforms another well-known scheduling algorithm. In addition, we have designed a recovery model which aims to improve handling of critical maintenance workload. Although the model is intentionally intended for system recovery, it can also be applied to many other contexts.

XQuery is a flexible language for querying XML data across a variety of storage methods. This thesis is a part of iAD, an ongoing research effort in next generation information access solutions. iAD is hosted by Fast Search & Transfer, a company developing their next search engine platform MARS. This project seeks to investigate the utilisation of XQuery as a query language for MARS. The result of this project is a novel method of translation, dubbed “Tainting Dependencies” (TD), which seeks to avoid unecessary denormalisation of intermediate results, and is designed specifically for translation to MARS’ relational algebra. This method supports a large subset of XQuery features. Furthermore, we have developed a prototype implementation which supports basic constructs such as FLWOR and sequence construction. TD is then compared head-on to a similar method dubbed “Loop Lifting”, and the results of this comparison is evaluated through discussion. The outcome of this project is a novel and well-documented method for translation of XQuery to MQL – a method which is designed to perform equally or better than existing implementations.

Digital cameras in mobile phones have become very popular in the recent years, and it is common to have large photo collections stored in the phone. Organizing these photos on the phone is still a big problem though. This study explores different ways of utilizing the location of where the photos were taken to make it easier to manage a large photo collection. Several different positioning technologies that can be used to obtain the location of where a photo was taken are presented. Three of the application suggestions for using location information of photos were implemented as prototypes on the Android platform. Android is a new platform for mobile phones developed by Google and the Open Handset Alliance, which has been made available as a preview release for developers. A part of this study was to investigate how suitable this platform is for developing location-based software. It was found that it is very suitable, although there still are some bugs and missing features that are expected to be fixed before the final release. The three application prototypes that were implemented were called “From Photo to Map”, “From Map to Photos” and “Who Lives Here?” The “From Photo to Map” application lets the user see a map where the location of a selected photo is visualized with a marker. The “From Map to Photos” application shows a map with markers at all of the locations where the user has taken photos. When one of the markers is selected, the photos taken at that location is shown. The “Who Lives Here?” application lets the user know which of the persons in his contact list that lives where the photo was taken. A small user survey showed that the participants thought all of the applications could be useful, but they were not so sure if they would use them themselves. The survey also showed that most of the users were able to find photos faster when using map-based browsing in the “From Map to Photos” application than when browsing through a photo collection linearly, but several concerns about the implementation details and the use of an emulator make the exact efficiency gain very uncertain.

The focus of this work is querying relational data through an object-relational mapper (ORM). In Java projects, it is common to use the Hibernate ORM and write the queries using HQL and Criteria. These approaches have limitations in regard to readability and static analysis. The limitations are identified and explained in this thesis. Several possible solutions are discussed. One of the solutions is looked at in depth and implemented in a real world project. The described solution eases the construction of queries and provides a way to fully utilize the development support tools.

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