User's and Administrator's Manual of AMGA Metadata Catalog v 2.4.0 (EMI-3)

User's and Administrator's Manual of AMGA Metadata Catalog v 2.4.0 (EMI-3

Theory and Practice of Transactional Method Caching

Nowadays, tiered architectures are widely accepted for constructing large scale information systems. In this context application servers often form the bottleneck for a system's efficiency. An application server exposes an object oriented interface consisting of set of methods which are accessed by potentially remote clients. The idea of method caching is to store results of read-only method invocations with respect to the application server's interface on the client side. If the client invokes the same method with the same arguments again, the corresponding result can be taken from the cache without contacting the server. It has been shown that this approach can considerably improve a real world system's efficiency. This paper extends the concept of method caching by addressing the case where clients wrap related method invocations in ACID transactions. Demarcating sequences of method calls in this way is supported by many important application server standards. In this context the paper presents an architecture, a theory and an efficient protocol for maintaining full transactional consistency and in particular serializability when using a method cache on the client side. In order to create a protocol for scheduling cached method results, the paper extends a classical transaction formalism. Based on this extension, a recovery protocol and an optimistic serializability protocol are derived. The latter one differs from traditional transactional cache protocols in many essential ways. An efficiency experiment validates the approach: Using the cache a system's performance and scalability are considerably improved

Gathering experience in trust-based interactions

As advances in mobile and embedded technologies coupled with progress in adhoc networking fuel the shift towards ubiquitous computing systems it is becoming increasingly clear that security is a major concern. While this is true of all computing paradigms, the characteristics of ubiquitous systems amplify this concern by promoting spontaneous interaction between diverse heterogeneous entities across administrative boundaries [5]. Entities cannot therefore rely on a specific control authority and will have no global view of the state of the system. To facilitate collaboration with unfamiliar counterparts therefore requires that an entity takes a proactive approach to self-protection. We conjecture that trust management is the best way to provide support for such self-protection measures

Analysis of current middleware used in peer-to-peer and grid implementations for enhancement by catallactic mechanisms

This deliverable describes the work done in task 3.1, Middleware analysis: Analysis of current middleware used in peer-to-peer and grid implementations for enhancement by catallactic mechanisms from work package 3, Middleware Implementation. The document is divided in four parts: The introduction with application scenarios and middleware requirements, Catnets middleware architecture, evaluation of existing middleware toolkits, and conclusions. -- Die Arbeit definiert Anforderungen an Grid und Peer-to-Peer Middleware Architekturen und analysiert diese auf ihre Eignung für die prototypische Umsetzung der Katallaxie. Eine Middleware-Architektur für die Umsetzung der Katallaxie in Application Layer Netzwerken wird vorgestellt.Grid Computing

The state of peer-to-peer network simulators

Networking research often relies on simulation in order to test and evaluate new ideas. An important requirement of this process is that results must be reproducible so that other researchers can replicate, validate and extend existing work. We look at the landscape of simulators for research in peer-to-peer (P2P) networks by conducting a survey of a combined total of over 280 papers from before and after 2007 (the year of the last survey in this area), and comment on the large quantity of research using bespoke, closed-source simulators. We propose a set of criteria that P2P simulators should meet, and poll the P2P research community for their agreement. We aim to drive the community towards performing their experiments on simulators that allow for others to validate their results

Fault Tolerant Distributed Computing Framework for Scientific Algorithms

Arvuti riistvara füüsilised piirangud on lõpetanud protsessorite tuumade arvutusvõimsuse suurenemist, kuid arvutiarhitektuuride suurenev parallelsus säilitab Moore'i seaduse kehtivust. Samal ajal tõuseb arvutusvõimsuse nõudlus pidevalt, sundides inimesi kohandada algoritme paralleelsete arhitektuuride kasutamiseks. Üks paljudest paralleelsete arhitektuuride probleemidest on tõrkete tekkimise tõenäosuse suurenemine parallelsete komponentide arvu suurenemisega. Piinlikult paralleelsete ja andmemahukate algoritmidega seoses on MapReduce läbinud pika tee, et tagada kasutajatele suure hulga hajutatud arvutiressursside lihtsustatud kasutamine ilma töö kaotamise hirmuta. Sama ei sa öelda kommunikatsiooni intensiivsete algoritmide jaoks mis on levinud teadusarvutuse domeenis. Selles töös on pakutud uus BSP ({\it Bulk Synchronous Parallel}) inspireeritud parallelprogrammeerimise mudel, mille lähenemisviis on sarnane {\it continuation passing} programmeerimis stiiliga ja mis võimaldab rakendada BSP struktuuril baseeruvat loomulikku tõrkekindlust. Töös on kirjeldatud loodud hajusarvutuste raamistik NEWT, mis põhineb pakutud mudelil ja on kasutatud selle lähenemisviisi valideerimiseks. Raamistik säilitab enamik MapReduce eelisi ning efektiivsemalt toetab suuremat algoritmide hulka, nagu näiteks eelmainitud iteratiivsed algoritmid.The physical limitations of computing hardware have put a stop on the increase of a single processor core's computing power. However, Moore's law is still maintained through the ever increasing parallelism of the computing architectures. At the same time the demand for computational power has been unrelentingly growing, forcing people to adapt the algorithms they use to these parallel architectures. One of the many downsides to parallel architectures is that with the rise in the number of components, the chance of failure of one of these components increases. When it comes to embarrassingly parallel data-intensive algorithms, Map-Reduce has gone a long way in ensuring users can easily utilize large amounts of distributed computing resources without the fear of losing work. However, this does not apply to iterative communication-intensive algorithms common in the scientific computing domain. In this work a new BSP-inspired (Bulk Synchronous Parallel) programming model is proposed, which adopts an approach similar to continuation passing for implementing parallel algorithms and facilitates fault-tolerance inherent in the BSP program structure. The distributed computing framework NEWT, which is based on the proposed model, is described and used to validate the approach. The framework retains most of the advantages that Map-Reduce provides, yet efficiently supports a larger assortment of algorithms, such as the aforementioned iterative ones