10894513
Block-Level Consistency of Replicated Files
11155402
The effect of failure and repair distributions on consistency protocols for replicated data objects
The accessibility of vital information can be enhanced by replicating the data on several sites, and employing a consistency control protocol to manage the copies.
Various protocols have been proposed to ensure that only current copies of the data can be accessed. The effect these protocols have on the accessibility of the replicated data is investigated by simulating the operation of the network and measuring the performance. Several strategies for replica maintenance are considered, and the benefits of each are analyzed. The details of the simulations are discussed. Measurements of the reliability and the availability of the replicated data are compared and contrasted.
The sensitivity of the Available Copy and Dynamic-linear Voting protocols to common patterns of site failures and repairs is studied in detail. Exponential, Erlang, uniform, and hyperexponential distributions are considered, and the effect the second moments have on the results is analyzed. The relative performance of competing protocols is shown to be only marginally affected by non-exponential distributions, validating the robustness of the exponential approximations.
8531327
Towards automatic shaping in robot navigation
Shaping is a potentially powerful tool in reinforcement learning applications. Shaping often fails to function effectively because of a lack of understanding about its effects when applied in reinforcement learning settings and the use of inadequate algorithms in its implementation. Due to these difficulties current shaping techniques require some form of manual intervention. We examine some of the principles involved in shaping and present a new algorithm for automatic transferral of knowledge, which uses the Q-values established in a previous task to guide exploration in the learning of a new task. This algorithm is applied to two different but related robot navigation tasks.
5226548
Parsing with an Extended Domain of Locality
One of the claimed benefits of Tree Adjoining Grammars is that they have an extended domain of locality (EDOL). We consider how this can be exploited to limit the need for feature structure unification during parsing. We compare two wide-coverage lexicalized grammars of English, LEXSYS and XTAG, finding that the two grammars exploit EDOL in different ways.
7294316
The Second Release of the RASP System
We describe the new release of the RASP (robust accurate statistical parsing) system, designed for syntactic annotation of free text. The new version includes a revised and more semantically-motivated output representation, an enhanced grammar and part-of-speech tagger lexicon, and a more flexible and semi-supervised training method for the structural parse ranking model. We evaluate the released version on the WSJ using a relational evaluation scheme, and describe how the new release allows users to enhance performance using (in-domain) lexical information.
15595014
Notification and awareness: synchronizing task-oriented collaborative activity
People working collaboratively must establish and maintain awareness of one another's intentions, actions and results. Notification systems typically support awareness of the presence, tasks and actions of collaborators, but they do not adequately support awareness of persistent and complex activities. We analysed awareness breakdowns in use of our Virtual School system--stemming from problems related to the collaborative situation, group, task and tool support--to motivate the concept of activity awareness. Activity awareness builds on prior conceptions of social and action awareness, but emphasizes the importance of activity context factors like planning and coordination. This work suggests design strategies for notification systems to better support collaborative activity.
2269827
Training wheels in a user interface
New users of high-function application systems can become frustrated and confused by the errors they make in the early stages of learning. A training interface for a commercial word processor was designed to make typical and troublesome error states “unreachable,” thus eliminating the sources of some new-user learning problems. Creating a training environment from the basic function of the system itself afforded substantially faster learning coupled with better learning achievement and better performance on a comprehension post-test. A control group spent almost a quarter of their time recovering from the error states that the training interface blocked off. We speculate on how this training strategy might be refined, and more generally, on how function should be organized in a user interface.