NASA Scientific and Technical Aerospace Reports

20060001877 New York Univ., New York, NY USA
Modeling of Concurrent Web Sessions with Bounded Inconsistency in Shared Data
Totok, Alexander; Karamcheti, Vijay; Jan. 1, 2005; 20 pp.; In English
Contract(s)/Grant(s): N66001-00-1-8920; N66001-01-1-8929
Report No.(s): AD-A440429; CIMS-TR-2005-868; No Copyright; Avail.: Defense Technical Information Center (DTIC)
Client interactions with modern web-accessible network services are typically organized into sessions involving multiple
requests that read and write shared application data. Therefore when executed concurrently, web sessions may invalidate each
other’s data. Depending on the nature of the business represented by the service, allowing the session with invalid data to
progress might lead to financial penalties for the service provider, while blocking the session’s progress and deferring its
execution (e.g., by relaying its handling to the customer service) will most probably result in user dissatisfaction. A
compromise would be to tolerate some bounded data inconsistency, which would allow most of the sessions to progress, while
limiting the potential financial loss incurred by the service. In order to quantitatively reason about these tradeoffs, the service
provider can benefit from models that predict metrics, such as the percentage of successfully completed sessions, for a certain
degree of tolerable data inconsistency. This paper develops such analytical models of concurrent web sessions with bounded
inconsistency in shared data for three popular concurrency control algorithms. We illustrate our models using the sample buyer
scenario from the TPC-W e-Commerce benchmark, and validate them by showing their close correspondence to measured
results of concurrent session execution in both a simulated and a real web server environment. Our models take as input
parameters of service usage, which can be obtained through profiling of incoming client requests. We augment our web
application server environment with a profiling and automated decision making infrastructure which is shown to successfully
choose, based on the specified performance metric, the best concurrency control algorithm in real time in response to changing
service usage patterns.
DTIC
Computerized Simulation; Internets; Mathematical Models
20060001890 California Polytechnic State Univ., San Luis Obispo, CA USA
Proceedings of the Annual ONR/CADRC Decision-Support Workshop (6th), Held in Quantico, Virginia, on 8-9 Sep
2004. Interoperability
Pohl, Jens G.; Nov. 1, 2004; 313 pp.; In English
Report No.(s): AD-A440458; No Copyright; Avail.: Defense Technical Information Center (DTIC)
In my introduction to this year’s conference I will address six questions that I believe come to the core of our conference
theme of interoperability. Do we human beings resist change? Is it in fact a human problem and not a technical problem that
we are dealing with? Can non-human intelligence exist? Do we even have a need for intelligent software? How did software,
particularly intelligent software (i.e., if we accept that there is such a thing) evolve over the past several decades, and what
is all this talk about a Semantic Web environment? And, finally, what does the future hold in the next five to ten years?
DTIC
Conferences; Decision Support Systems; Interoperability
20060001891 Maryland Univ., College Park, MD USA
Using Rhythms of Relationships to Understand Email Archives
Perer, Adam; Shneiderman, Ben; Oard, Douglas W.; Jan. 1, 2005; 21 pp.; In English; Original contains color illustrations
Contract(s)/Grant(s): N66001-00-2-8910
Report No.(s): AD-A440461; No Copyright; Avail.: Defense Technical Information Center (DTIC)
Due to email’s ubiquitous nature, millions of users are intimate with the technology. However, most users are only
familiar with managing their own email, which is an inherently different task than exploring an email archive. Historians and
social scientists believe that email archives are important artifacts for understanding the individuals and communities they
represent. In order to understand the conversations evidenced in an archive, context is needed. In this paper, we present a new
way to gain this necessary context: analyzing the temporal rhythms of social relationships. We provide methods for
constructing meaningful rhythms from the email headers by identifying relationships and interpreting their attributes. With
these visualization techniques, email archive explorers can uncover insights that may have been otherwise hidden in the
archive. We apply our methods to an individual’s fifteen-year email archive, which consists of about 45,000 messages and over
4, 000 relationships.
DTIC
Documents; Electronic Mail
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