Mobile support in CSCW applications and groupware development frameworks

Computer Supported Cooperative Work (CSCW) is an established subset of the field of Human Computer Interaction that deals with the how people use computing technology to enhance group interaction and collaboration. Mobile CSCW has emerged as a result of the progression from personal desktop computing to the mobile device platforms that are ubiquitous today. CSCW aims to not only connect people and facilitate communication through using computers; it aims to provide conceptual models coupled with technology to manage, mediate, and assist collaborative processes. Mobile CSCW research looks to fulfil these aims through the adoption of mobile technology and consideration for the mobile user. Facilitating collaboration using mobile devices brings new challenges. Some of these challenges are inherent to the nature of the device hardware, while others focus on the understanding of how to engineer software to maximize effectiveness for the end-users. This paper reviews seminal and state-of-the-art cooperative software applications and development frameworks, and their support for mobile devices

Conflict-Free Replicated Data Types in Dynamic Environments

Over the years, mobile devices have become increasingly popular and gained improved computation capabilities allowing them to perform more complex tasks such as collaborative applications. Given the weak characteristic properties of mobile networks, which represent highly dynamic environments where users may experience regular involuntary disconnection periods, the big question arises of how to maintain data consistency. This issue is most pronounced in collaborative environments where multiple users interact with each other, sharing a replicated state that may diverge due to concurrency conflicts and loss of updates. To maintain consistency, one of today’s best solutions is Conflict-Free Replicated Data Types (CRDTs), which ensure low latency values and automatic conflict resolution, guaranteeing eventual consistency of the shared data. However, a limitation often found on CRDTs and the systems that employ them is the need for the knowledge of the replicas whom the state changes must be disseminated to. This constitutes a problem since it is inconceivable to maintain said knowledge in an environment where clients may leave and join at any given time and consequently get disconnected due to mobile network communications unreliability. In this thesis, we present the study and extension of the CRDT concept to dynamic environments by introducing the developed P/S-CRDTs model, where CRDTs are coupled with the publisher/subscriber interaction scheme and additional mechanisms to ensure users are able to cooperate and maintain consistency whilst accounting for the consequent volatile behaviors of mobile networks. The experimental results show that in volatile scenarios of disconnection, mobile users in collaborative activity maintain consistency among themselves and when compared to other available CRDT models, the P/S-CRDTs model is able to decouple the required knowledge of whom the updates must be disseminated to, while ensuring appropriate network traffic values

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

Total order in opportunistic networks

Opportunistic network applications are usually assumed to work only with unordered immutable messages, like photos, videos, or music files, while applications that depend on ordered or mutable messages, like chat or shared contents editing applications, are ignored. In this paper, we examine how total ordering can be achieved in an opportunistic network. By leveraging on existing dissemination and causal order algorithms, we propose a commutative replicated data type algorithm on the basis of Logoot for achieving total order without using tombstones in opportunistic networks where message delivery is not guaranteed by the routing layer. Our algorithm is designed to use the nature of the opportunistic network to reduce the metadata size compared to the original Logoot, and even to achieve in some cases higher hit rates compared to the dissemination algorithms when no order is enforced. Finally, we present the results of the experiments for the new algorithm by using an opportunistic network emulator, mobility traces, and Wikipedia pages.Peer ReviewedPostprint (author's final draft

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