User-Relative Names for Globally Connected Personal Devices

Nontechnical users who own increasingly ubiquitous network-enabled personal devices such as laptops, digital cameras, and smart phones need a simple, intuitive, and secure way to share information and services between their devices. User Information Architecture, or UIA, is a novel naming and peer-to-peer connectivity architecture addressing this need. Users assign UIA names by "introducing" devices to each other on a common local-area network, but these names remain securely bound to their target as devices migrate. Multiple devices owned by the same user, once introduced, automatically merge their namespaces to form a distributed "personal cluster" that the owner can access or modify from any of his devices. Instead of requiring users to allocate globally unique names from a central authority, UIA enables users to assign their own "user-relative" names both to their own devices and to other users. With UIA, for example, Alice can always access her iPod from any of her own personal devices at any location via the name "ipod", and her friend Bob can access her iPod via a relative name like "ipod.Alice".Comment: 7 pages, 1 figure, 1 tabl

Media Distribution in a Pervasive Computing Environment

Distribution of media in the fast growing world of digital stored content and multimedia supporting devices with connectivity, calls for a new media distribution architecture. The user should be provided with the experience of having an overview of his full media collection, regardless of the time, the place, and the connectivity. Transparent distributed data management is crucial to Ambient Intelligent applications. The proposed media distribution architecture offers a possible solution. It provides the user with the experience of having all his media collections available at any time, in any place, and managing them regardless of connection availability in the heterogeneous environment. This experience is enabled in our system by the separation of metadata and content handling. Other features are efficient handling of snapshots, usage of various database technologies, and leveraging device and service discovery mechanisms

Adaptive Consistency Guarantees for Large-Scale Replicated Services

To maintain consistency, designers of replicated services have traditionally been forced to choose from either strong consistency guarantees or none at all. Realizing that a continuum between strong and optimistic consistencies is semantically meaningful for a broad range of network services, previous research has proposed a continuous consistency model for replicated services to support the tradeoff between the guaranteed consistency level, performance and availability. However, to meet changing application needs and to make the model useful for interactive users of large-scale replicated services, the adaptability and the swiftness of inconsistency resolution are important and challenging. This paper presents IDEA (an Infrastructure for DEtection-based Adaptive consistency guarantees) for adaptive consistency guarantees of large-scale, Internet-based replicated services. The main functions enabled by IDEA include quick inconsistency detection and resolution, consistency adaptation and quantified consistency level guarantees. Through experimentation on the Planet-Lab, IDEA is evaluated from two aspects: its adaptive consistency guarantees and its performance for inconsistency resolution. Results show that IDEA is able to provide consistency guarantees adaptive to user’s changing needs, and it achieves low delay for inconsistency resolution and incurs small communication overhead

Replikation im mobilen Pflegeassistenzsystem MARIKA

Mit dem derzeitigen demografischen Wandel nimmt auch die Bedeutung der häuslichen Gesundheitspflege stark zu. Professionelle Pflegedienste unterliegen dabei einer gesetzlichen Dokumentationspflicht. Die Dokumentation von Pflegeaktivitäten ist eine sehr zeitaufwendige Tätigkeit und nimmt bis zu 40% der täglichen Arbeitszeit in Anspruch. Durch automatische Dokumentation ist es möglich, das Pflegepersonal zu unterstützen, so dass letztendlich mehr Zeit für die eigentlichen Pflegetätigkeiten bleibt. Das in dieser Arbeit vorgestellte Projekt MARIKA beschäftigt sich mit der Entwicklung einer globalen Pflegedokumentations- und Koordinationsplattform. Diese soll das Pflegepersonal durch automatische Aufzeichnung der erbrachten Pflegetätigkeiten unterstützen. Durch Rückschlüsse aus der Analyse und Auswertung dokumentierter Tätigkeiten kann die Planung täglicher Arbeitsabläufe verbessert und die Auslastung vorhandener Ressourcen optimiert werden. Ein Kernbestandteil des Systems bilden Geräte für den ambulanten mobilen Pflegeeinsatz. Nach Aufzeichnung der erbrachten Pflegetätigkeiten werden die aufgezeichneten Daten zwischen den Komponenten des Systems repliziert. Für den Einsatz in verteilten Datenbanksystemen mit mobilen Teilnehmern werden spezielle Replikationsverfahren vorgestellt

Collaboration and Document Editing on Bandwidth-Limited Devices

This paper presents the design of CoFi, a novel architecture for supporting document editing and collaborative work over bandwidth-limited clients. CoFi combines the previously disjoint notions of consistency and fidelity in a unified architecture. CoFi enables bandwidth-limited clients to edit documents that are only partially present at the client (because parts of the documents were lossily transcoded, or only a portion of the document was fetched), and to propagate modifications incrementally by progressively increasing their fidelity

Optimistic Replication and Resolution

International audienceData replication places physical copies of a shared logical item onto different sites. Optimistic replication (OR) allows a program at some site to read or update the local replica at any time. An update is tentative because it may conflict with a remote update. Such conflicts are resolved after the fact, in the background. Replicas may diverge occasionally but are expected to converge eventually

Mobile transaction management in mobisnap

Lecture Notes in Computer Science, 1884To allow mobile users to continue their work while disconnected, mobile systems usually rely on optimistic replication techniques. In mobile database systems, mobile units cache subsets of the database state and allow disconnected users to perform transactions concurrently. These transactions are later integrated in the master database state. As concurrently performed transactions may conflict, it is usually impossible to determine the result of an update in the mobile unit. Moreover, this model differs from the traditional client/server model due to the fundamental fact that the user will usually not be connected to the system when the results of his transactions are finally determined - therefore, he can not immediately perform adequate alternative actions. In this paper we describe a transaction management system that takes into consideration the above-mentioned characteristics. Transactions are specified as mobile transactional programs, which allows the precise definition of operation semantics and the definition of alternative actions. Support for active user notification is also provided in the system. Finally, the system relies on a reservation mechanism to be able to guarantee the results of transactions in the mobile units.(undefined

PaRiS: Causally Consistent Transactions with Non-blocking Reads and Partial Replication

Geo-replicated data platforms are at the backbone of several large-scale online services. Transactional Causal Consistency (TCC) is an attractive consistency level for building such platforms. TCC avoids many anomalies of eventual consistency, eschews the synchronization costs of strong consistency, and supports interactive read-write transactions. Partial replication is another attractive design choice for building geo-replicated platforms, as it increases the storage capacity and reduces update propagation costs. This paper presents PaRiS, the first TCC system that supports partial replication and implements non-blocking parallel read operations, whose latency is paramount for the performance of read-intensive applications. PaRiS relies on a novel protocol to track dependencies, called Universal Stable Time (UST). By means of a lightweight background gossip process, UST identifies a snapshot of the data that has been installed by every DC in the system. Hence, transactions can consistently read from such a snapshot on any server in any replication site without having to block. Moreover, PaRiS requires only one timestamp to track dependencies and define transactional snapshots, thereby achieving resource efficiency and scalability. We evaluate PaRiS on a large-scale AWS deployment composed of up to 10 replication sites. We show that PaRiS scales well with the number of DCs and partitions, while being able to handle larger data-sets than existing solutions that assume full replication. We also demonstrate a performance gain of non-blocking reads vs. a blocking alternative (up to 1.47x higher throughput with 5.91x lower latency for read-dominated workloads and up to 1.46x higher throughput with 20.56x lower latency for write-heavy workloads)