Research report : Collaborative Peer 2 Peer Edition: Avoiding Conflicts is Better than Solving Conflicts

Collaborative edition is achieved by distinct sites that work independently on (a copy of) a shared document. Conflicts may arise during this process and must be solved by the collaborative editor. In pure Peer to Peer collaborative editing, no centralization nor locks nor time-stamps are used which make conflict resolution difficult. We propose an algorithm which relies on the notion or semantics dependence and avoids the need of any integration transformation to solve conflicts. Furthermore, it doesn't use any history file recording operations performed since starting the edition process. We show how to define editing operations for semi-structured documents i.e. XML-like trees, that are enriched with informations derived for free from the editing process. Then we define the semantics dependence relation required by the algorithm and we present preliminary results obtained by a prototype implementation.Comment: 12 page

Lightweight incremental application upgrade

I present a lightweight approach to incremental application upgrade in the context of component-based software development. The approach can be used to efficiently implement an automated update feature in a platform and programming language agnostic way. A formal release model is presented which ensures consistency and allows the computation of incremental updates. Finally I show how this model can be implemented on top of Subversio

Supporting Collaborative Writing of XML Documents

Data management is a key issue in cooperative systems. Anyone who uses more than one computer or collaborates with other people is aware of the problems posed by having multiple copies of shared documents. Most existing synchronization tools are specific to a particular type of shared data i.e. text files, calendars, XML files. Therefore, user should use several tools to maintain their different copies up-to-date. This is not an easy task. To address this issue, we defined a generic synchronization framework based on the operational transformation approach. This framework allows to synchronise text files, calendars, XML files by using the same tool. The main objective of this paper is to present this framework and how it is used to support cooperative writing of XML document. An implementation is illustrated through the revision control system called So6, which is a part of a distributed collaborative technology called LibreSource

Data replication and update propagation in XML P2P data management systems

XML P2P data management systems are P2P systems that use XML as the underlying data format shared between peers in the network. These systems aim to bring the benefits of XML and P2P systems to the distributed data management field. However, P2P systems are known for their lack of central control and high degree of autonomy. Peers may leave the network at any time at will, increasing the risk of data loss. Despite this, most research in XML P2P systems focus on novel and efficient XML indexing and retrieval techniques. Mechanisms for ensuring data availability in XML P2P systems has received comparatively little attention. This project attempts to address this issue. We design an XML P2P data management framework to improve data availability. This framework includes mechanisms for wide-spread data replication, replica location and update propagation. It allows XML documents to be broken down into fragments. By doing so, we aim to reduce the cost of replicating data by distributing smaller XML fragments throughout the network rather than entire documents. To tackle the data replication problem, we propose a suite of selection and placement algorithms that may be interchanged to form a particular replication strategy. To support the placement of replicas anywhere in the network, we use a Fragment Location Catalogue, a global index that maintains the locations of replicas. We also propose a lazy update propagation algorithm to propagate updates to replicas. Experiments show that the data replication algorithms improve data availability in our experimental network environment. We also find that breaking XML documents into smaller pieces and replicating those instead of whole XML documents considerably reduces the replication cost, but at the price of some loss in data availability. For the update propagation tests, we find that the probability that queries return up-to-date results increases, but improvements to the algorithm are necessary to handle environments with high update rates

Robuste und kontextbezogene Ausführung mobiler Aktivitäten in Prozessumgebungen

IT-Trendanalysten sehen das Thema "Mobilität" als eine wichtige Säule nachhaltiger IT-Lösungen. Der Trend in Richtung mobiler IT-Anwendungen wird maßgeblich durch Millenials getrieben, d.h. Menschen die mit dem digitalen Zeitalter aufgewachsen sind. Diese erwarten insbesondere auch eine Integration von Smart-Mobilgeräten in bestehende IT-Lösungen. In Bezug auf Prozess-Management-Technologie bedeutet dieser Trend, dass Smart-Mobilgeräte in IT-gestützte Arbeits- bzw. Prozessabläufe nahtlos integriert werden können müssen. Insbesondere sollten sowohl einzelne Aktivitäten (d.h. Prozessschritte) als auch ganze Prozessfragmente (d.h. Ausschnitte eines Prozesses) auf Smart-Mobilgeräten ausführbar sein. Die vorliegende Arbeit adressiert eine solche Integration von Prozess-Management-Technologie und Smart-Mobilgeräten. Konkret wird untersucht, wie ausgewählte Aktivitäten eines Prozesses robust und kontextbezogen auf Smart-Mobilgeräten ausgeführt werden können und welche weitergehenden Anforderungen sich für mobil ausgeführte Aktivitäten im Vergleich zur Ausführung von Aktivitäten auf stationären Systemen ergeben. Da Smart-Mobilgeräte beschränkte Ressourcen besitzen und das Risiko eines Ausfalls höher als bei stationären Systemen ist, erfordern diese Aspekte tiefergehende Untersuchungen. Darüber hinaus erfordert die Unterstützung mobiler Aktivitäten eine technische Umgebung, in der Prozesse ausgeführt werden (sog. Prozessumgebung). Die Arbeit zeigt, dass die nahtlose Integration von Smart-Mobilgeräten in eine Prozessumgebung einen mobilen Kontext (d.h. Attribute wie z.B. Ausführungsort, Geräteeigenschaften und Netzverbindung) erfordert. Auf dessen Basis wird ein umfassendes Rahmenwerk eingeführt, mit dem sich mobile Aktivitäten robust und kontextbezogen in einer Prozessumgebung ausführen lassen. Das Rahmenwerk fußt auf fünf technischen Säulen, deren Konzepte die robuste und kontextbezogene Ausführung bewerkstelligen. Darüber hinaus wird gezeigt, wie sich die vorgestellte Lösung in existierende Prozess-Management-Technologie integrieren lässt. Insgesamt eröffnet eine robuste und kontextbezogene Ausführung mobiler Aktivitäten in einer Prozessumgebung neue Perspektiven für die Einbindung von Endanwendern in ihre Prozesse

Exploiting schemas in data synchronization

Increased reliance on optimistic data replication has led to burgeoning interest in tools and frameworks for synchronizing disconnected updates to replicated data. But good data synchronizers are challenging both to specify and to build. We have implemented a generic synchronization framework, called Harmony, that can be used to build state-based synchronizers for a wide variety of tree-structured data formats. A novel feature of this framework is that the synchronization process—in particular, the recognition of conflicts—is driven by the schema of the structures being synchronized. We formalize Harmony’s synchronization algorithm, prove that it obeys a simple and intuitive specification, and illustrate, using simple address books as a case study, how it can be used to synchronize trees representing a variety of specific forms of application data, including sets, records, tuples, and relations