18641869
Checkpointing Distributed Shared Memory
Distributed shared memory (DSM) is a very promising programming model for exploiting the parallelism of distributed memory systems, because it provides a higher level of abstraction than simple message passing. Although the nodes of standard distributed systems exhibit high crash rates only very few DSM environments have some kind of support for fault-tolerance.In this article, we present a checkpointing mechanism for a DSM system that is efficient and portable. It offers some portability because it is built on top of MPI and uses only the services offered by MPI and a POSIX compliant local file system.As far as we know, this is the first real implementation of such a scheme for DSM. Along with the description of the algorithm we present experimental results obtained in a cluster of workstations. We hope that our research shows that efficient, transparent and portable checkpointing is viable for DSM systems.
12469936
JAMES: A Platform of Mobile Agents for the Management of Telecommunication Networks
This paper presents an overview of JAMES, a Java-based platform of mobile agents that is mainly oriented for the management of data and telecommunication networks. This platform has been developed on behalf of a Eureka Project (Σ!1921) and the project partners are Siemens SA, University of Coimbra and Siemens AG. We describe the main architecture of the platform giving more emphasis to the most important features. To show the effectiveness of some of the techniques that have been implemented we will present some performance results that compare the JAMES platform with the Aglets Workbench. 
 
The main target of our platform is network management and telecommunication applications. In this line, we have done a Java-based implementation of SNMP that has been integrated within the platform. The industrial partners of our project (i.e. Siemens S.A.) have developed a prototype application for TMN performance management. Although it is still a prototype it is being used to validate the technological advantages of using mobile agents in the management of telecommunication networks.
9570610
Towards Manageable Mobile Agent Infrastructures
This paper addresses the problem of managing distributed mobile agent infrastructures. First, the weaknesses of current mobile agent implementations will be discussed and identified from the manageability viewpoint. The solutions devised and experimented in order to alleviate these weaknesses in our own agent platform will then be presented. These solutions are generic and could easily be applied to the majority of existing mobile agent implementations. The paper will finish with the discussion of a new approach we are following in the M&M Project, based on a rather different architecture that significantly reduces the manageability requirements.
7711926
A flexible mobile-agent framework for accessing information systems in disconnected computing environments
Over the last few years, the importance of mobile computing has been steadily increasing. While it is important to provide support for accessing databases in disconnected computing environments, many of the information systems being deployed today are using a three-tier architecture. It is becoming vital to find ways of providing reliable access to the business logic present in the middle-tier for mobile applications. The authors present a component based framework that enables client applications to send mobile agents to interact with application servers in disconnected computing environments. This framework allows the applications to benefit from the advantages of using mobile agents in disconnected computing environments, and at the same time provides integration between mobile clients and corporate information systems.
6164806
Deterministic Models of Software Aging and Optimal Rejuvenation Schedules
Automated modeling of software aging processes is a prerequisite for cost-effective usage of adaptive software rejuvenation as a self-healing technique. We consider the problem of such automated modeling in server-type applications whose performance degrades depending on the "work" done since last rejuvenation, for example the number of served requests. This type of performance degradation - caused mostly by resource depletion - is common, as we illustrate in a study of the popular Axis Soap server 1.3. In particular, we propose deterministic models for approximating the leading indicators of aging and an automated procedure for statistical testing of their correctness. We further demonstrate how to use these models for finding optimal rejuvenation schedules under utility functions. Our focus is on the important case that the utility function is the average of a performance metric (such as maximum service rate). We also consider optional SLA constraints under which the performance should never drop below a specified level. Our approach is verified by a study of the aging processes in the Axis Soap 1.3 server. The experiments show that the deterministic modeling technique is appropriate in this case, and that the optimization of rejuvenation schedules can greatly improve the average maximum service rate of an aging application.
12117022
Distributed data collection through remote probing in windows environments
Distributed data collector (DDC) is a framework to ease and automate repetitive executions of console applications (probes) over a set of LAN networked Windows personal computers. The framework allows for the remote execution of probes, providing support for collecting the execution output of probes (standard output and standard error). Additionally, right after a probe execution, the output can be parsed and processed by user-defined code (post collecting code) that can act accordingly to user's needs. The framework can be useful to perform repetitive large-scale monitoring and administrative tasks over machines with transient availability, that is, machines that present no guarantees of being available at a given time. A major strength of DDC lies in the fact that it does not require installation of software in remote nodes, avoiding administrative burdens that remote daemons and alike normally provoke. Besides presenting the data collection framework, the paper discusses the results of a 30-day monitoring experiment conducted with DDC. The experiment collected resource usage metrics over 169 Windows machines from classroom laboratories of an academic institution.
9436195
Satisfiability models and algorithms for circuit delay computation
The existence of false paths represents a significant and computationally complex problem in the estimation of the true delay of combinational and sequential circuits. In this article we conduct a comprehensive study of modeling circuit delay computation, accounting for false paths, as a sequence of instances of Boolean satisfiability. Several path sensitization models and delay models are studied. In addition we evaluate some of the most competitive Boolean satisfiability algorithms seeking to identify which are best suited for solving circuit delay computation problems. Finally, realistic delay modeling (taking into account extracted interconnect delays and fanout data) is considered in order to experimentally evaluate the complexity of solving real-world instances.
14564941
PetroGrapher: managing petrographic data and knowledge using an intelligent database application
This paper describes the PetroGrapher system, an intelligent database application to support petrographic analysis, interpretation of oil reservoir rocks, and management of relevant data using resources from both knowledge-based system technology and database technology. In this project, the visual tacit knowledge applied in petrographic analysis was rendered explicit through the collection of cases (rock descriptions), which were then used in the development of a domain ontology organized in a partonomy. Expert-level basic features, which we call ‘visual chunks’, were identified. The cases were further compared against the ontology to elucidate the relations between features in descriptions of rocks, visual chunks and expert interpretations. The domain knowledge was represented through a set of frames and knowledge graphs. The knowledge graphs are applied to recognize the visual chunks in the user data and retrieved the related interpretation. The system was developed as a structure tightly coupled with a relational database system, which acts as a repository for the knowledge base and the user data, and an object-oriented component, which preserves the semantics of data and develops inferences. The system was validated by three groups of users with different levels of expertise. q 2003 Elsevier Ltd. All rights reserved.
1299949
Sociable Interfaces
Interface formalisms are able to model both the input requirements and the output behavior of system components; they support both bottom-up component-based design, and top-down design refinement. In this paper, we propose “sociable” interface formalisms, endowed with a rich compositional semantics that facilitates their use in design and modeling. Specifically, we introduce interface models that can communicate via both actions and shared variables, and where communication and synchronization covers the full spectrum, from one-to-one, to one-to-many, many-to-one, and many-to-many. Thanks to the expressive power of interface formalisms, this rich compositional semantics can be realized in an economical way, on the basis of a few basic principles. We show how the algorithms for composing, checking the compatibility, and refining the resulting sociable interfaces can be implemented symbolically, leading to efficient implementations.
16534842
Formal Verification of Component-Based Software Systems
In this work we present a methodology for formal modeling and verification of component based software systems. The methodology is based on software architecture, components, and reuse of Petri Nets models. With this process, we are contributing for the visual composition, verification, and formal validation of software. We also show an example of the application of this methodology into two different domains.
528194
Algorithms for solving Boolean satisfiability in combinational circuits
Boolean satisfiability is a ubiquitous modeling tool in Electronic Design Automation (EDA). It finds application in test pattern generation, delay-fault testing, combinational equivalence checking and circuit delay computation, among many other problems. Moreover Boolean satisfiability is in the core of algorithms for solving binate covering problems. This paper describes how Boolean satisfiability algorithms can take circuit structure into account when solving instances derived from combinational circuits. Potential advantages include smaller run times, the utilization of circuit-specific search pruning techniques, avoiding the overspecification problem that characterizes Boolean satisfiability testers, and reducing the time for iteratively generating instances of SAT from circuits. The experimental results obtained on several benchmark examples in two different problem domains display dramatic reductions in the run times of the algorithms, and provide clear evidence that computed solutions can have significantly less specified variable assignments than those obtained with common SAT algorithms.