VC2-providing awareness in off-the-shelf version control systems

Version control systems have been used to help groups of people working at the same or distributed sites to cooperatively create documents. In particular, these systems are very popular in distributed collaborative software development. However, even using these systems, users often perform concurrent changes that require manual con ict resolution. Important causes for this situation are the lack of mutual awareness and coordination, among developers, and reluctance to commit unstable modifications. The paper addresses this problem by providing a tool that integrates with offthe-shelf version control systems and monitors filesystem accesses to relevant files in order to enhance the awareness among developers. With VC2 users can be aware of uncommitted changes made by remote users; receive request to commit their own changes; be advised to update their local versions. While the final decision is always under user control, the team is made aware of the level of risk when delaying commits and updates

Reconciliation for mobile computing environments with portable storage devices

Mobile computing environments have changed in recent years with the increasing use of different types of portable devices, ranging from mobile phones to laptops, and from MP3 players to portable storage devices (e.g. flash disks). Many of these devices have large amounts of storage, allowing users to transport most of their data with them. In this paper we briefly present the FEW file management system, a system that aims to ease file management in this new mobile environment. In particular, we detail the automatic reconciliation approach used in this system based on operational transformation. We motivate our work with a study of conflicts in data managed by version control systems

Automating semantics-based reconciliation for mobile transactions

International audienceOptimistic replication lets multiple users update local replicas of shared data independently. These replicas may diverge and must be reconciled. In this paper, we present a general-purpose reconciliation system for mobile transactions. The basic reconciliation engine treats reconciliation as an optimization problem. To direct the search, it relies on semantic information and user intents expressed as relations among mobile transactions. Unlike previous semantics-based reconciliation systems, our system includes a module that automatically infers semantic relations from the code of mobile transactions. Thus, it is possible to use semantics-based reconciliation without incurring the overhead of specifying the semantics of the data types or operations

FEW : file management for portable devices

Comunicação apresentada ao International Workshop on Software Support for Portable Storage (IWSSPS), San Francisco, 2005.In recent years, an increasing number of portable devices with large amounts of storage have become widely used. In this paper, we present the early design of the FEW system, a system that aims to ease file management in the new mobile environment. To this end, the system will manage file replicas stored in fixed and portable storage devices. It will provide an automatic mechanism to establish new file replicas by analyzing file system activity. The system will automatically and incrementally synchronize all file replicas exploring the available network connectivity and the availability of portable storage devices. To merge concurrent updates, operational transformation techniques will be used.FCT/MCES POSI/FEDER - Project #59064/2004

Building a Flexible Object-Group-Oriented Framework to support Large Scale Cooperative and Adaptive Applications

In this paper we examine the requirements of large scale cooperative applications, namely those alternating multi-part synchronous work sessions with variable periods of asynchronous interactions and disconnected work. We discuss the topological organization of the large scale cooperative space and the materialization of an integrated generic platform to support those requirements. Our approach emphasizes the need of an adequate programming support. We will describe and characterize an object-grouporiented layered and wrapped infrastructure as a contribution to build generic programming frameworks offering high degree of orthogonality and, consequently, high flexibility. Key words: Large Scale Distributed Computing Systems (LSDCS), Flexibility, Computer Support for Collaborative Work (CSCW), Group Communication Group-Dissemination, Distributed Programming,, Object Group-Orientation, Collaborative Object-Group Orientation 1. Introduction Distributed systems and infrastructures provid..

SqlIceCube: Automatic Semantics-based Reconciliation for Mobile Databases

In a distributed system, optimistic replication enables users on different sites to query and update their local replicas of shared databases without a priori synchronization. Replicas may diverge, and updates must be reconciled; reconciliation is a difficult problem in the presence of conflicts, alternative execution paths, and dependencies between transactions. We present SqlIce-Cube, a general-purpose reconciliation system. SqlIceCube automatically extracts significant semantic relations from the program text of transactions. Examples of relations are a transaction that depends on another, helps another, hinders another, constitutes an alternative to another, etc. In turn these semantic relations feed into the SqlIceCube scheduler, which generates and executes a combination of transactions with the highest possible value. The approach is general and supports combinations of transactions across a variety of different applications. Application experience and benchmarks show the viability of the approach. SqlIceCube correctly extracts semantic relations from an interesting variety of application transactions, performs well, and scales well to large input sizes.

Routing Algorithms for Content-based Publish/Subscribe Systems

Publish/subscribe systems allow many parties to communicate by way of many-to-many message exchanges. These systems can be topic- or content-based. In topic-based systems, message flows are statically partitioned and each flow is associated with a so called topic, group or channel. For efficiency and convenience purposes, content-based systems allow subscribers to provide semantic filters over the contents of the notifications. Content-based networking is a generalization of the content-based publish/subscribe model, such that networking messages are no longer addressed to the identifiers of the communication end-points (e.g. network or group addresses). Messages are published into a distributed (information) space and routed by the networking substrate to the “interested ” communication end-points. Naming, binding and communication are intertwined in the same substrate. Routing in a topic-based distributed publish/subscribe system is a problem similar to the multicasting routing problem and uses similar algorithms to determine and maintain the dissemination trees. An extra level of complexity is introduced by requiring that messages are filtered and useless transmissions be avoided. Thus, dissemination trees must be dynamically pruned, message by message, to only cover matching subscribers. This paper presents a compilation of the main proposed algorithms to route notifications in distributed content-based publish-subscribe systems, published in the last decade. It differs from surveys published on the broad topic of publish/subscribe systems by focusing the analysis on the content-based routing problem in respect to optimality, complexity and applicability. Moreover, whenever it is relevant, the algorithms covered are linked with similar algorithms developed and used by the networking community. This helps to put the content-based routing problem into perspective. 1