18643244
An Empirical Performance Study on PSIM
It is well known that errors caught in the early stages of system development life cycle greatly helped reduce the expense for later error fixing and mitigate risks and complications. Performance analysis is one of the methods to ensure satisfactory system performance that can avoid redesign and patch in the later stage of system development when performance problems emerge. Much work has been done to address such concerns collectively known as the 'performance engineering' problem. However, a comprehensive method is still needed to provide an end-to-end support for performance evaluation on software architecture design. Automated tools to support the method must be developed, and its validation must be carefully planned and conducted. In response to this need, we propose our approach, PSIM (performance simulation and modeling). PSIM is a performance simulation and modeling tool that integrated performance properties into software architecture specifications expressed in several major UML diagrams. PSIM models can be transformed into Colored GSPN (colored generalized stochastic Petri nets) via an automated tool. As a result, the Colored GSPN models can be simulated to perform model-based performance evaluation. In this paper PSIM is first briefly reviewed and illustrated through modeling a web-based electronic conferencing system, called M-Net, to derive performance metrics. We then conduct runtime performance testing to the implementation of M-Net and compare the simulation results against the runtime testing data. PSIM is shown to be effective in predicting system performance and in identifying system performance bottlenecks through this experimentation.
10778870
An empirical performance study for validating a performance analysis approach: PSIM
Performance analysis gains more attention in recent years by researchers who focus their study on the early software development stages to mitigate the risk of redesign as problems emerge later. Previously we proposed PSIM (a performance simulation and modeling tool) that integrated performance properties into software architecture specifications expressed in several major UML diagrams. PSIM models can be transformed into colored GSPN and the colored GSPN models can then be simulated to perform model-based performance evaluation. In this paper we briefly review the PSIM approach and apply it to model a Web-based conferencing system, called M-Net, to derive performance metrics. We then conduct runtime performance testing to the implementation of M-Net and compare the simulation data to runtime testing data. The comparison results show the effectiveness of the PSIM method in predicting system performance and identifying system performance bottlenecks.
10317156
A research on Collaboration Net
We present research on computer-supported cooperative work by introducing an approach to the multimedia based net-centric conference environment-Collaboration Net. Some basic definitions of the distributed Web-based meeting are provided, and the properties of this kind of collaboration are given. We explain problems associated with the well-known yet old-fashioned parliamentary procedure, Robert's Rules of Order, which must be formally modeled and adapted to the modern net-centric virtual conference where time synchronism is hard to enforce. A prototype of our Web-browser based approach to developing the Collaboration Net is also briefly presented. Finally, research challenges in this area are highlighted.
36323277
Event-Based Traceability for Managing Evolutionary Change
Although the benefits of requirements traceability are widely recognized, the actual practice of maintaining a traceability scheme is not always entirely successful. The traceability infrastructure underlying a software system tends to erode over its lifetime, as time-pressured practitioners fail to consistently maintain links and update impacted artifacts each time a change occurs, even with the support of automated systems. This paper proposes a new method of traceability based upon event-notification and is applicable even in a heterogeneous and globally distributed development environment. Traceable artifacts are no longer tightly coupled but are linked through an event service, which creates an environment in which change is handled more efficiently, and artifacts and their related links are maintained in a restorable state. The method also supports enhanced project management for the process of updating and maintaining the system artifacts.
40684547
Supporting event based traceability through high-level recognition of change events
Although requirements traceability is crucial in both the development and maintenance of a software system, traceability links and related artifacts tend to deteriorate, as time-pressured practitioners fail to systematically update them in response to change. Event-based traceability addresses this issue by establishing links through a loosely coupled publisher/subscriber scheme. Dependent entities subscribe to requirements and receive event notifications as changes occur. This paper focuses upon the role played by the requirements specification as a publisher of events. A set of standard change events is defined and a method for monitoring a user's actions within a requirements management environment and the subsequent recognition and publication of the change events is proposed. Early results obtained from testing this approach are reported.
35042753
A Binary Single-Key-Lock System for Access Control
A binary coding method was invented and has been applied to the single-key-lock (SKL) system which achieves access control by associating with each accesser only one key and with each resource only one lock. The new system is called the binary single-key-lock (BSKL) system. In both the SKL and BSKL systems, through operations on the single-key-lock pair, the control information can be revealed. On the basis of the new binary coding method, and because binary operations are much faster, better performance for such an access control system can be achieved. The increased extensibility of the modification is also discussed. >
8773045
Characterizing and Exploiting Reference Locality in Data Stream Applications
In this paper, we investigate a new approach to process queries in data stream applications. We show that reference locality characteristics of data streams could be exploited in the design of superior and flexible data stream query processing techniques. We identify two different causes of reference locality: popularity over long time scales and temporal correlations over shorter time scales. An elegant mathematical model is shown to precisely quantify the degree of those sources of locality. Furthermore, we analyze the impact of locality-awareness on achievable performance gains over traditional algorithms on applications such asMAX-subset approximate sliding window join and approximate count estimation. In a comprehensive experimental study, we compare several existing algorithms against our locality-aware algorithms over a number of real datasets. The results validate the usefulness and efficiency of our approach.
34152454
Self-organizing topological tree
The self-organizing maps (SOM) introduced by Kohonen implemented two important operations: vector quantization (VQ) and a topology-preserving mapping. In this paper, a tree structured SOM algorithm named self-organizing topological tree (SOTT) is proposed. Unlike the conventional tree structured SOMs as stated in T. Kohonen (2001), P. Koikkalainnen and E. Oja (1990) and P. Koikkalainnen (1994), every layer of the proposed SOTT is organized simultaneously instead of layer by layer. A reduction of computational complexity from O(N) to O(logN) is achieved by the tree structured search in both the training phase and the test phase. Furthermore, such topological tree that maintains both intra-layer and inter-layer topologies during and after learning can be seen as endowing the SOM topological map with the progressive decoding and multi-resolution capabilities.
17968637
Robust localization of multiple events in sensor networks
Localization of events is a canonical problem for sensor networks, especially for applications such as intrusion detection or neighborhood monitoring. We employ a general sensor model which models various types of sensor nodes. However, traditional triangulation method will be unsolvable when the sensor nodes are positioned on a line. To overcome such ill-conditioned cases, we can use MAP or MMSE methods to estimate event locations. Moreover, to locate multiple simultaneous events and overcome the ill-conditioned case when the sensor nodes are collinear, we need to solve a system of nonlinear equations. We propose a novel method which solves this system of nonlinear equations and multiple-event locations can be found. Experiments and error analysis of the method demonstrate the performance of our methods
33610290
Biomimetic Robotics