Publications from 2008

The migration from desktop applications to Web-based services is scattering personal data across a myriad of Web sites, such as Google, Flickr, YouTube, and Amazon S3. This dispersal poses new challenges for users, making it more difficult for them to: (1) organize, search, and archive their data, much of which is now hosted by Web sites; (2) create heterogeneous, multi-Web-service object collections and share them in a protected way; and (3) manipulate their data with standard applications or scripts.

In this paper, we show that a Web-service interface supporting standardized naming, protection, and object-access services can solve these problems and can greatly simplify the creation of a new generation of object-management services for the Web. We describe the implementation of Menagerie, a proof-of-concept prototype that provides these services for Web-based applications. At a high level, Menagerie creates an integrated file and object system from heterogeneous, personal Web-service objects dispersed across the Internet. We present several object-management applications we developed on Menagerie to show the practicality and benefits of our approach.

Response time is one of the most important factors for the overall usability of a computer system. We present RSIO, a processor scheduling framework for improv- ing the response time of latency-sensitive applications by monitoring accesses to I/O channels and inferring when user interactions occur. RSIO provides a general mech- anism for all user interactions, including direct interac- tions via local HCI devices such as mouse and keyboard, indirect interactions through middleware, and remote in- teractions through networks. It automatically and dy- namically identifies processes involved in a user inter- action and boosts their priorities at the time the inter- action occurs to improve system response time. RSIO detects processes that directly handle a user interaction as well as those indirectly involved in processing the in- teraction, automatically accounting for dependencies and boosting their priorities accordingly. RSIO works with existing schedulers, processes that may mix interactive and batch activities, and requires no application modifi- cations to identify periods of latency-sensitive applica- tion activity. We have implemented RSIO in Linux and measured its effectiveness on microbenchmarks and real applications. Our results show that RSIO is easy to use and can provide substantial improvements in system per- formance for latency-sensitive applications.

The objective of the study was to develop and implement an architecture for remote training that can be used in the narrowband home telemedi- cine environment. A remote training architecture, the REmote Patient Education in a Telemedicine Environment (REPETE) architecture, using a remote control protocol (RCP) was developed. A set of design criteria was specified. The developed architecture was integrated into the IDEATel home telemedicine unit (HTU) and evaluated against these design criteria using a combination of technical and expert evaluations. Technical evaluation of the architecture demonstrated that remote cur- sor movements and positioning displayed on the HTU were smooth and effectively real-time. The trainers were able to observe within approximately 2 seconds lag what the patient sees on their HTU screen. Evaluation of the architecture by experts was favorable. Responses to a Likert scale questionnaire regarding audio quality and remote con- trol performance indicated that the expert evaluators thought that the audio quality and remote control performance were adequate for remote training. All evaluators strongly agreed that the system would be useful for training patients. The REPETE architecture supports basic training needs over a narrowband dial-up connection. We were able to maintain an audio chat simultaneously with performing a remote training ses- sion, while maintaining both acceptable audio quality and remote con- trol performance. The RCP provides a mechanism to provide training without requiring a trainer to go to the patient’s home and effectively supports deictic referencing to on screen objects.

Fault-tolerant, replicated file systems are a crucial component of today's data centers. Despite their huge complexity, these systems are typically specified only in brief prose, which makes them difficult to reason about or verify. This paper describes the authors' experience using formal methods to improve our understanding of and confidence in the behavior of replicated file systems. We wrote formal specifications for three real-world fault-tolerant file systems and used them to: (1) expose design similarities and differences; (2) clarify and mechanically verify consistency properties; and (3) evaluate design alternatives. Our experience showed that formal specifications for these systems were easy to produce, useful for a deep understanding of system functions, and valuable for system comparison.