Summary form only given. Hybrid systems are systems which combine both continuous variable and discrete event dynamics. Their complexity has risen to the extent that traditional approaches which dealt separately with ...
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Summary form only given. Hybrid systems are systems which combine both continuous variable and discrete event dynamics. Their complexity has risen to the extent that traditional approaches which dealt separately with the continuous and discrete aspects of such systems have become obsolete. Instead of proposing a novel formal notation for the specification of controllers for hybrid systems we have developed extended real time Logic (ERTL) as a formal notation for the modelling and analysis of relative and absolute timing properties of hybrid systems. ERTL embeds the discrete system model of the real time logic (RTL) of Jahanian and Mok (1986, 1988) into continuous time, and adds the ability to reason about piecewise continuous functions using predicates over real valued variables. While RTL is able to formally describe the behaviour of computational entities in the time domain, ERTL also permits the formal description of the behaviour of physical entities in both value and time domains.
Real time logic (RTL) was introduced as a formalism for reasoning about the relative and absolute timing properties of computational tasks of discrete real-time systems. Extended real time logic (ERTL) is a formalism ...
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Real time logic (RTL) was introduced as a formalism for reasoning about the relative and absolute timing properties of computational tasks of discrete real-time systems. Extended real time logic (ERTL) is a formalism for the modelling and analysis of relative and absolute timing properties of hybrid systems (systems that combine continuous variables and discrete event dynamics). The extensions provided by ERTL enable the modelling of system behaviour ranging from activities of the physical entities that form part of the environment of a computing system, to the temporal ordering of the computational tasks of the computing system itself thus providing a formal notation that can be used in all stages of software development.
We discuss ASPECT, a first step towards a generic specification technique for software architectures. We present and discuss an abstract grammar for ASPECT that lists and relates to each other all the architectural el...
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We discuss ASPECT, a first step towards a generic specification technique for software architectures. We present and discuss an abstract grammar for ASPECT that lists and relates to each other all the architectural elements that form ASPECT's vocabulary. After elaborating on the characteristics of these architectural elements, we illustrate their application in a small example.
We propose a method for integrating a preexisting conventional database system with a multimedia server in a multidatabase environment. In the multidatabase environment, changes to the preexisting database system are ...
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We propose a method for integrating a preexisting conventional database system with a multimedia server in a multidatabase environment. In the multidatabase environment, changes to the preexisting database system are not allowed because such changes are too expensive. For the integration, high-level semantic description of multimedia data is modeled using the enhanced entity-relationship (EER) model to support content-based retrieval of multimedia data. The EER design is translated into a schema of the preexisting database system and then the translated schema is integrated with the preexisting database schema. The content description can be used to locate pertinent multimedia data, and the identifiers are used to access the multimedia data stored in the multimedia server. However, with only a simple schema representation of the semantic description of multimedia data, high levels of recall and precision of queries may not be obtained because conventional database systems provide only exact matching answers to the query. Thus, we extended the conventional query processing mechanism by providing a modified cooperative query answering mechanism.
Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance...
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ISBN:
(纸本)9780897918541
Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance problems. However, modern virtual memory found in recent operating systems such as Cenju-3/DE give application writers control over virtual memory policies. We demonstrate that custom virtual memory policies can dramatically reduce virtual memory overhead and allow applications to run out-of-core efficiently. We also demonstrate that the main advantage of virtual memory, namely programming simplicity, is not lost.
To obtain large speed-up factors in Monte Carlo simulation using importance sampling (IS), the modification, or bias of the underlying probability measures must be carefully chosen. In this paper, we utilize the stoch...
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To obtain large speed-up factors in Monte Carlo simulation using importance sampling (IS), the modification, or bias of the underlying probability measures must be carefully chosen. In this paper, we utilize the stochastic gradient descent (SGD) algorithm, which uses stochastic gradient optimization techniques, to arrive at favorable IS bias parameter settings for the simulation of tandem queues with bursty traffic, geometric service times and a finite buffer. We describe in detail the experimental method associated with applying the SGD algorithm. Speed-up factors of 1 to 8 orders of magnitude over conventional Monte Carlo estimation of the cell loss probability are achieved for the examples presented.
It is a generally accepted concept that multiple views are needed in object-oriented analysis or domain analysis techniques. Three commonly adopted models for requirements analysis include object model, functional mod...
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It is a generally accepted concept that multiple views are needed in object-oriented analysis or domain analysis techniques. Three commonly adopted models for requirements analysis include object model, functional model and dynamic model. This paper introduces and incorporates the concept of relational modeling into the analysis techniques. Relational modeling mainly deals with two tasks: classification of semantic relations and identification of higher-order system causal relations. Classification of semantic relations supports comparison and evaluation of various relations, which in turn can be used to select suitable methods to process the relations. A higher-order relation depicts the relations between different relations as opposed to the relations between objects often discussed in object modeling. A network of higher-order relations reveals the cause-effect dependency relationships and can facilitate understanding and reasoning of application systems. Furthermore, incorporation of relational modeling techniques can support software reuse in an application domain or across domains.
Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance...
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Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance problems. However, modern virtual memory found in recent operating systems such as Cenju-3/DE give application writers control over virtual memory policies. We demonstrate that custom virtual memory policies can dramatically reduce virtual memory overhead and allow applications to run out-of-core efficiently. We also demonstrate that the main advantage of virtual memory, namely programming simplicity, is not lost.
The Earth Observing System (EOS) Data and Information System (EOSDIS) is perhaps one of the most important examples of large-scale, geographically distributed, and data intensive systems. The paper presents various fa...
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The Earth Observing System (EOS) Data and Information System (EOSDIS) is perhaps one of the most important examples of large-scale, geographically distributed, and data intensive systems. The paper presents various facets of a data and information architecture for EOSDIS. EOS data is organized by means of an object-oriented schema, while EOS knowledge is organized through multiple domain-specific thesauri, complemented by domain knowledge and rules. The information holdings are organized into the source data archives, a data warehouse which provides an integrated view of the information holdings, and information marts which generate value-added information products for specialized user communities. Finally a federated client-server architecture is proposed to allow non-EOSDIS systems to become members of the EOSDIS community, allowing them to access EOSDIS holdings, and sharing their own data with EOSDIS.
LAN systems are widely used in distributed environment and it becomes more indispensable to manage distributed LAN systems in an integrated manner as enterprise-level networks. This paper describes the LAN fault manag...
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LAN systems are widely used in distributed environment and it becomes more indispensable to manage distributed LAN systems in an integrated manner as enterprise-level networks. This paper describes the LAN fault management ensemble which has been developed by the Ensemble Team of INTAP NM (Network Management) Technical Committee. Ensembles represent specific solutions to particular problems of the networks as a collection of managed resources, functions and scenarios. This ensemble provides a method of managing an enterprise-level private network in particular fault management areas. OSI management is adopted as a platform to manage LANs which are assumed to be managed by SNMP or OSI layer management protocols. This ensemble takes a state-oriented approach which is better suited, and provides more efficient integrated network management for large-scale enterprise networks containing many resources to be managed, because SNMP management is performed by polling based on the stateless approach. In addition, this ensemble adopts international standards or publicly available specifications regarding the necessary management information. Integrated management is executed by the OSI manager and proxy agents. Proxy agents act as OSI agents and convert information gathered by SNMP manager/agents or OSI layer management entities to OSI. Various network resources such as FDDI, Ethernet and MIB-II are defined on the basis of definition of the ISO/IEC, IEEE and NM Forum standards and additional necessary resources are uniquely defined for this ensemble requirements.
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