支持网络建模和仿真的Modelica模型管理框架

针对基于Modelica的多领域仿真模型组织方式不能支持模型的网络化共享控制及网络环境下在线建模仿真的问题,提出一种支持网络环境下建模与仿真的Modelica模型管理框架。首先分析了现有Modelica模型组织方式在支持网络多用户模式下的模型共享及建模仿真方面的问题,然后提出了基于数据库与文件仓相结合解决方案,既支持Modelica知识模型的网络共享,又支持网络环境在线建模与仿真。最后基于该模型管理框架开发实现基于网络的多领域统一建模仿真平台。     

A web services framework for distributed model management

Distributed model management aims to support the wide-spread sharing and usage of decision support models. Web services is a promising technology for supporting distributed model management activities such as model creation and delivery, model composition, model execution and model maintenance to fulfill dynamic decision-support and problem solving requests. We propose a web services based framework for model management (called MM-WS) to support various activities of the model management life cycle. The framework is based on the recently proposed Integrated Service Planning and Execution (ISP & E) approach for web services integration. We discuss encoding of domain knowledge (as individual models) and utilize the MM-WS framework to interleave synthesis of composite models with their execution. A prototypical implementation with an example is used to illustrate the utility of the framework to enable distributed model management and knowledge integration. Benefits and issues of using the framework to support model-based decision-making in organizational contexts are outlined.

A framework for ranking uncertain distributed database

Distribution and uncertainty are considered as the most important design issues in database applications nowadays. A lot of ranking or top-k query processing techniques are introduced to solve the problems of communication cost and centralized processing. On the other hand, many techniques are also developed for modeling and managing uncertain databases. Although these techniques were efficient, they didn't deal with distributed data uncertainty. This paper proposes a framework that deals with both data distribution and uncertainty based on ranking queries. Within the proposed framework, communication and computation-efficient algorithms are investigated for retrieving the top-k tuples from distributed sites. The main objective of these algorithms is to reduce the communication rounds utilized and amount of data transmitted while achieving efficient ranking. Experimental results show that both proposed techniques have a great impact in reducing communication cost. Both techniques are efficient but in different situations. The first one is efficient in the case of low number of sites while the other achieves better performance at higher number of sites.     

The SIRIUS-DELTA architecture: A framework for co-operating database systems

SIRIUS-DELTA is a distributed database system which is aimed at co-operation of heterogeneous local database systems. It illustrates how the Open Systems approach has been used in the context of distributed database systems, mainly in its architecture and its Data Manipulation Protocol. It also illustrates that distributed databases is an area where co-operation between ISO/TC97/SC5 Programming Languages and ISO/TC97/SC16 Open Systems Interconnection sub-committees is of a major importance for future developments.     

A relational framework for join implementation in model management systems

Two important issues in the design of relational model banks are the degree to which they should be aggregated or disaggregated and the methods by which disaggregated model banks might be integrated in response to user queries. Three topics relevant to this issue are addressed in this paper. The first is whether a universal model and its projections may possess the lossy join property. We will show that they do not. The second is the development of a relational algebra for the specification of join implementation in model banks, and the third is the realization of such an algebra in a language similar to Query-by-Example.     

A compiler model for a relational data base management system

One of the chief difficulties which needs to be overcome during the early design stages of a system is that of establishing a satisfactory design for that system. From the time it was first conceived it was apparent that the Relational Data Base Management System is like a compiler in so far as it takes a succession of user requests for information formulated in an applied predicate calculus and translates each one into a series of calls which access an underlying data base and transform data from that data base into the form the user wishes to see. This paper compares the architecture of the Relational Data Base Management System with that of a compiler, and then demonstrates the use of the architecture when processing a language based on an applied predicate calculus. Finally, the paper describes a number of extensions to that architecture which are required to solve the particular problems raised by the data base system.     

A Logical Framework for Knowledge Base Maintenance

The maintenance sequences of a knowledge base and their limits are introduced.Some concepts used in knowledge base maintenance,such as new laws,user‘s rejections,and reconstructions of a knowledge base are defined;the related theorems are proved.A procedure is defined using transition systems;it generates maintenance sequences for a given user‘s model and a knowledge base.It is proved that all sequences produced by the procedure are convergent,and their limit is the set of true sentences of the model.Some computational aspects of reconstructions are studied.An R-calculus is given to deduce a reconstruction when a knowledge base meets a user‘s rejection.The work is compared with AGM‘s theory of belief revision.     

面向对象的模型库与数据库接口技术

DSS中的模型可以用不同语言,按照不同的规范编写,所以模型的数据格式各不相同,如何从数据库中获取所需格式的数据是开发决策支持系统必需解决的问题.设计了面向对象模型库结构,提出了一种使用规范的数据描述文件(MDF)进行模型封装的方法,实现了规范化的面向对象的模型库与数据库接口.     

The Hidden Information State model: A practical framework for POMDP-based spoken dialogue management

This paper explains how Partially Observable Markov Decision Processes (POMDPs) can provide a principled mathematical framework for modelling the inherent uncertainty in spoken dialogue systems. It briefly summarises the basic mathematics and explains why exact optimisation is intractable. It then describes in some detail a form of approximation called the Hidden Information State model which does scale and which can be used to build practical systems. A prototype HIS system for the tourist information domain is evaluated and compared with a baseline MDP system using both user simulations and a live user trial. The results give strong support to the central contention that the POMDP-based framework is both a tractable and powerful approach to building more robust spoken dialogue systems.     

A framework for project management

Various technologies have been developed to try to realize the ideal of a fully integrated project support environment, including: centralized repositories, complex configuration management systems, process modelling and workflow, cooperating objects. The different approaches have led to a number of partial solutions and it has often proved difficult to integrate two or more of them to give more complete lifecycle coverage or a more complete view. This paper sets out some requirements for support environments for the management of software engineering projects by considering the major elements that constitute such a project and the necessary interactions between those elements.     

A database for medical image management

MEDIMAN (Medical Image MANagement) is a web information system (WIS) for medical image management and processing currently used by neuroscientists and clinicians at several medical and research centres in Spain for research and clinical trials. While developing the MEDIMAN database (DB) we encountered several design challenges unlike those arising in traditional DBs. This paper describes the development of MEDIMAN focusing on the database and the use of the database development process proposed in Midas, a model-driven framework for WIS development. Special attention is given to the design decisions made at each stage to address the challenges encountered.     

A framework for efficient regression tests on database applications

Regression testing is an important software maintenance activity to ensure the integrity of a software after modification. However, most methods and tools developed for software testing today do not work well for database applications; these tools only work well if applications are stateless or tests can be designed in such a way that they do not alter the state. To execute tests for database applications efficiently, the challenge is to control the state of the database during testing and to order the test runs such that expensive database reset operations that bring the database into the right state need to be executed as seldom as possible. This work devises a regression testing framework for database applications so that test runs can be executed in parallel. The goal is to achieve linear speed-up and/or exploit the available resources as well as possible. This problem is challenging because parallel testing needs to consider both load balancing and controlling the state of the database. Experimental results show that test run execution can achieve linear speed-up by using the proposed framework.     

A relational database integrity framework for access control policies

Access control is one of the most common and versatile mechanisms used for information systems security enforcement. An access control model formally describes how to decide whether an access request should be granted or denied. Since the role-based access control initiative has been proposed in the 90s, several access control models have been studied in the literature. An access control policy is an instance of a model. It defines the set of basic facts used in the decision process. Policies must satisfy a set of constraints defined in the model, which reflect some high level organization requirements. First-order logic has been advocated for some time as a suitable framework for access control models. Many frameworks have been proposed, focusing mainly on expressing complex access control models. However, though formally expressed, constraints are not defined in a unified language that could lead to some well-founded and generic enforcement procedures. Therefore, we make a clear distinction by proposing a logical framework focusing primarily on constraints, while keeping as much as possible a unified way of expressing constraints, policies, models, and reference monitors. This framework is closely tied to relational database integrity models. We then show how to use well-founded procedures in order to enforce and check constraints. Without requiring any rewriting previous to the inference process, these procedures provide clean and intuitive debugging traces for administrators. This approach is a step toward bridging the gap between general but hard to maintain formalisms and effective but insufficiently general ones.     

A database model for object dynamics

To effectively model complex applications in which constantly changing situations can be represented, a database system must be able to support the runtime specification of structural and behavioral nuances for objects on an individual or group basis. This paper introduces the role mechanism as an extension of object-oriented databases to support unanticipated behavioral oscillations for objects that may attain many types and share a single object identity. A role refers to the ability to represent object dynamics by seamlessly integrating idiosyncratic behavior, possibly in response to external events, with pre-existing object behavior specified at instance creation time. In this manner, the same object can simultaneously be an instance of different classes which symbolize the different roles that this object assumes. The role concept and its underlying linguistic scheme simplify the design requirements of complex applications that need to create and manipulate dynamic objects. Edited by D. McLeod / Received March 1994 / Accepted January 1996     

A database model for object dynamics

Due to a technical error, some figures of the above paper were not reproduced satisfactorily. They are printed again below: Edited by D. McLeod / Received March 1994 / Accepted January 1996     

A management framework for systems users

Many business managers today are in need of practical guidance in determining which information systems management practices are appropriate for their particular organization. Of central importance is the management of the information systems development process. A field research study was conducted at five major U.S. corporations to determine those information systems development management practices that had proved successful. The research method consisted of in-depth interviews with managers and technical people at each company. In addition, the reputation of each company as a successful manager of the information systems function was validated using a set of organizational performance criteria developed by a panel of prominent information systems professionals. The results of the research are presented in the form of a planning and control framework of successful management practices. The framework describes and classifies those practices common to all companies and clearly differentiates those practices which varied significantly among the companies studied. The framework is designed to enable management to readily identify those information system development practices that have proved successful and to select from among them those most appropriate to the local situation. It can also serve as a guide for self-study on the part of the individual manager.     

A flexible framework for consistency management

Recent distributed shared memory (DSM) systems provide increasingly more support for the sharing of objects rather than portions of memory. However, like earlier DSM systems these distributed shared object systems (DSO) still force developers to use a single protocol, or a small set of given protocols, for the sharing of application objects. This limitation prevents the applications from optimizing their communication behaviour and results in unnecessary overhead. A current general trend in software systems development is towards customizable systems, for example frameworks, reflection, and aspect‐oriented programming all aim to give the developer greater flexibility and control over the functionality and performance of their code. This paper describes a novel object‐oriented framework that defines a DSM system in terms of a consistency model and an underlying coherency protocol. Different consistency models and coherency protocols can be used within a single application because they can be customized, by the application programmer, on a per‐object basis. This allows application specific semantics to be exploited at a very fine level of granularity and with a resulting improvement in performance. The framework is implemented in JAVA and the speed‐up obtained by a number of applications that use the framework is reported. Copyright © 2002 John Wiley & Sons, Ltd.