Francisco J. Torres-Rojas

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Ordering and time are two different aspects of consistency of shared objects in a distributed system. One avoids conflicts between operations, the other addresses how quickly the effects of an operation are perceived by the rest of the system. Consistency models such as sequential consistency and causal consistency do not consider the particular time at(More)
In a Distributed System with N sites, the precise detection of causal relationships between events can only be done with vector clocks of size N. This gives rise to scalability and efficiency problems for logical clocks that can be used to order events accurately. In this paper we propose a class of logical clocks called plausible clocks that can be(More)
Techniques such as replication and caching of objects that implement distributed services lead to consistency problems that must be addressed. We explore new consistency protocols based on the notion of object value lifetimes. By keeping track of the lifetimes of the values stored in shared objects (i.e., the time interval that goes from the writing of a(More)
In systems that support disconnected operations, shared objects must be cached at client sites to ensure that the objects are accessible while the client is disconnected. It is desirable that objects cached at a client site are mutually consistent with respect to the level of consistency provided by the system. We present a new technique for detecting(More)
Given a distributed system with several shared objects and many processes concurrently updating and reading them, it is convenient that the system achieves convergence on the value of these objects. Such property can be guaranteed depending on the consistency model being employed. Causal Consistency is a weak consistency model that is easy and cheap to(More)
Many application domains have already demonstrated that they can benefit greatly if efficient access can be provided to shared information across widely distributed users. We use the generic term <i>object</i> to describe units of shared information which could include files, web pages or language defined objects. Future applications will require object(More)
Services targeted to the home environment must deal with software and hardware heterogeneity of client and server machines. Distributed object based middleware is attractive for building distributed services in such heterogeneous environments for a number of reasons. In particular, distributed objects can hide the complexities that arise from distribution(More)
Consistency is a necessary consideration when dealing with web caching. Although this technique accelerates the web experience for the user, it must provide consistency, i.e., the objects in the cache must be fresh and all the relationships among them must be valid. Both problems have been addressed by several web caching strategies ([4], [5], [7], [9],(More)