Automatic application object migration in sensor networks

Object migration in wireless sensor networks has the potential to reduce energy consumption for a wireless sensor network mesh. Automated migration reduces the need for the programmer to perform manual static analysis to find an efficient layout solution. Instead, the system can self-optimise and adjust to changing conditions. This paper describes an automated, transparent object migration system for wireless sensor networks, implemented on a micro Java virtual machine. The migration system moves objects at runtime around the sensor mesh to reduce communication overheads. The movement of objects is transparent to the application developer. Automated transparent object migration is a core component of Hydra, a distributed operating system for wireless sensor networks that is currently under development. Performance of the system under a complex performance test scenario using a real-world dataset of seismic events is described. The results show that under both simple and complex conditions the migration technique can result in lower data traffic and consequently lower overall energy cost

A database model for object dynamics.

Object-oriented database systems, Dynamic object re-classification, Object role model, Dynamic class hierarchy, Object migration

Online Bin Covering with Limited Migration

Semi-online models where decisions may be revoked in a limited way have been studied extensively in the last years. This is motivated by the fact that the pure online model is often too restrictive to model real-world applications, where some changes might be allowed. A well-studied measure of the amount of decisions that can be revoked is the migration factor beta: When an object o of size s(o) arrives, the decisions for objects of total size at most beta * s(o) may be revoked. Usually beta should be a constant. This means that a small object only leads to small changes. This measure has been successfully investigated for different, classical problems such as bin packing or makespan minimization. The dual of makespan minimization - the Santa Claus or machine covering problem - has also been studied, whereas the dual of bin packing - the bin covering problem - has not been looked at from such a perspective. In this work, we extensively study the bin covering problem with migration in different scenarios. We develop algorithms both for the static case - where only insertions are allowed - and for the dynamic case, where items may also depart. We also develop lower bounds for these scenarios both for amortized migration and for worst-case migration showing that our algorithms have nearly optimal migration factor and asymptotic competitive ratio (up to an arbitrary small epsilon). We therefore resolve the competitiveness of the bin covering problem with migration

Migration on request, a practical technique for preservation

Maintaining a digital object in a usable state over time is a crucial aspect of digital preservation. Existing methods of preserving have many drawbacks. This paper describes advanced techniques of data migration which can be used to support preservation more accurately and cost effectively. To ensure that preserved works can be rendered on current computer systems over time, “traditional migration” has been used to convert data into current formats. As the new format becomes obsolete another conversion is performed, etcetera. Traditional migration has many inherent problems as errors during transformation propagate throughout future transformations. CAMiLEON’s software longevity principles can be applied to a migration strategy, offering improvements over traditional migration. This new approach is named “Migration on Request.” Migration on Request shifts the burden of preservation onto a single tool, which is maintained over time. Always returning to the original format enables potential errors to be significantly reduced

Migration-by-Emulation Planets Web-Service

The availability of migration tools for older formats is often limited. Thus we suggest a different approach: using the original applications to access the object and transfer the latter into formats which can be accessed in today's environments. The appropriate environment for the digital artefacts could be provided through emulation. With the reproduction of the original environment, a large and diverse set of migration input/output paths becomes available. Working for the Open Planets Project the authors the authors created remotely accessible Web services integrated into the PLANETS testbed. These services demonstrate preservation workflows using migration together with the emulation of original environments

Object migration in temporal object-oriented databases

The paper presents T-ORM (Temporal Objects with Roles Model), an object-oriented data model based on the concepts of class and role. In order to represent the evolution of real-world entities, T-ORM allows objects to change state, roles and class in their lifetime. In particular, it handles structural and behavioral changes that occur in objects when they migrate from a given class to another. First, the paper introduces the basic features of the T-ORM data model, emphasizing those related to object migration. Then, it presents the query and manipulation languages associated with T-ORM, focusing on the treatment of the temporal aspects of object evolution

Database independent Migration of Objects into an Object-Relational Database

This paper reports on the CERN-based WISDOM project which is studying the serialisation and deserialisation of data to/from an object database (objectivity) and ORACLE 9i.Comment: 26 pages, 18 figures; CMS CERN Conference Report cr02_01

Process migration in UNIX environments

To support process migration in UNIX environments, the main problem is how to encapsulate the location dependent features of the system in such a way that a host independent virtual environment is maintained by the migration handlers on the behalf of each migrated process. An object-oriented approach is used to describe the interaction between a process and its environment. More specifically, environmental objects were introduced in UNIX systems to carry out the user-environment interaction. The implementation of the migration handlers is based on both the state consistency criterion and the property consistency criterion

When Beckett on Film migrated to television

In the migration of drama from one medium to another a text is reshaped, and different audiences are addressed by adaptations because of the process of remediation. This article evaluates the significance of the intermedial migrations that happened to the "Beckett on Film" project in which Samuel Beckett’s 19 theatre plays were performed on stage, then filmed for an international festival, then shown on television in the UK, USA, Ireland and elsewhere. The analysis focuses on the television versions and shows how their distribution and reception contexts framed their meanings in different ways, and assesses how medial migration destabilised the object of analysis itself at the same time as the work became able to address multiple audiences and fulfil different cultural roles