一种组通信模型在CORBA平台上的设计和实现

组通信是ＣＳＣＷ（ＣｏｍＰｕｔｅｒＳｕｐｐｒｏｔｅｄＣｏｏｐｅｒａｔｉｖｅＷｏｒｋ）应用中的关键问题。ＣＳＣＷ所属的协同应用（Ｃｏｏｐ－ｅｒａｔｉｖｅａｐｐｌｉｃａｔｉｏｎｓ）领域在分布系统应用中是一个很有前途的新领域。这种新型应用对分布技术提出了新的要求和挑战。在这种新的分布环境中，支持组通信的对象组模型是问题的关键所在。在文章中，作者基于ＣＯＲＢＡ平台，针对ＣＳＣＷ应用的要求，提出了一种对象组模型，介绍了组模型中各类对象之间的交互和协调关系，并给出了主要对象的接口定义语言（ＩＤＬ）的描述和说明。     

支持协同应用的一种组通信方案的设计和实现

协同在分布系统应用中是一个很有前途的新领域,该应用对分布技术提出了新的要求和挑战。在这种新的分布环境中,对象组模型是问题的关键所在。在本文中,我们基于ＣＯＲＢＡ平台,针对ＣＳＣＷ应用的要求,提出了一种对象组模型,介绍了组模型中各类对象之间的交互和协调关系,并给出了主要对象的接口定义语言的描述和说明。     

CSCW支撑平台的结构模型

传统分布式系统中面向系统的控制及分布透明性不能满足ＣＳＣＷ对面向用户的显式协作的要求。本文提出了一个ＣＳＣＷ系统的结构模型，该结构以一个ＣＳＣＷ支撑平台作为一般分布式系统与协作应用之间的适配层，来支持协作任务平台具有客户／服务器模式，它用面向对象方法处理各种异构性，将协作规则与协作机制分开，这样它就可以仅利用基本的分布功能，提供方便灵活的面向用户协作的服务。在此平台上可有各种多媒体协同应用，从而充     

基于知识的CSCW人机接口模型

人机接口是ＣＳＣＷ系统的重要组成部分，也是它的难点之一。本文针对ＣＳＣＷ系统中用主动作的协同特性，提出了一种协同人机接口结构模型ＫＣＨＣＩ，通过对用户动作的多层抽象和对动作结果的多层例化，实现多用户之间的多层次协同及感知，同时，以知识作为规范描述语言，不仅增强了接口的灵活性，提高了接口的协同效率，也方便了接口的开发。     

柔性协同事务模型

提出了一个ＣＳＣＷ领域中的高级事务处理模型－柔性协同事务模型ＦＣＴＭ。首先给出协同事务的定义。并描述协同事务的状态,然后从协同事务的状态角度刻画协同事务之间、协同事务与外部环境之间的复杂依赖关系,最后用协同事务的状态依赖描述可串行化正确性准则。ＦＣＴＭ的优点在于用户能够根据不同的ＣＳＣＷ应用领域的需求,灵活地定义协同事务的状态和状态依赖。     

轻型永久对象管理器缓存机制的设计与实现

信息系统中,理想的应用程序结构应该是基于对象模型的,但是数据几乎总是保存在关系数据库中。永久对象管理器的位置处于对象模型和关系模型之间,它将应用程序的对象映射到关系数据库的表中,从而对应用程序开发者隐藏了下层的实现,简化了应用程序的开发。缓存机制是构成永久对象管理器的重要组成部分,它通过缓存最近被访问过的对象来减少对数据库的访问。文中分析了一个对象缓存机制的设计和实现,并通过测试证明引入该缓存机制可以极大地提高系统的性能。     

基于图形的OODBMS实现技术

本文介绍了一种利用面向对象方法设计和实现的基于图形数据的面向对象数据库管理系统ＯＯＢＭＳ,它是用Ｂｏｒ－ｌａｎｄＣ＋＋和面向对象方法实现的。文章不仅介绍图形数据的结构、特点、管理方法,还介绍了ＯＯＤＢＭＳ的实现技术。界面部分包括：面向终端用户的交互式查询界面、面向应用程序员的数据库宿主语言器;数据模式定义子系统部分;数据模式定义、修改。一致性约束;对象管理子系统部分：对象管理器、类型管理器的方法管理器;存取子系统部分：数据库的存储组织和有效的管理。虽然本文所介绍的ＯＯＤＢＭＳ只是一个实验系统,但…     

基于分布式约束网络的协同设计研究

针对并行工程环境下的设计过程，提出基于分布式约束购物协同设计方法，该方法利用Agent分布式地表达设计中的各种约束关系，，通过Agent之间的动态协作实现约束网络的一致性维护，实时监测和协商消解设计冲突，使得设计约束得以分布，并发地满足，从而使得并行工程环境下的协同设计过程得到很好地支持。     

工程信息结构的语义模型

本文提出一种新的语义模型，该模型能够支持ＣＩＭ工程中相互联系的各类数据的结构化管理。首先定义了问题范围内的对象与对象类；在研究对象间联系的基础上建立起对象、对象类之间的语义关系；然后定义了作用于语义关系和对象上的操作，从而得出一种面向工程信息结构的语义模型。模型描述了一个项目的层次结构。通过在共享对象上建立等价语义关系，能够将项目的层次结构图转化为项目树，进而可用树结构实现对ＣＩＭ工程中产品及各类     

基于对象的分布式实时系统调度模型研究

为了解决分布式实时系统有关分配和调度等问题，给出并用形式化方法描述了一种基于对象分布式实时系统调度的通用模型。该模型包括表示时限的绝对时间约束，表示周期属性的周期约束，表示各种前趋关系和同步要求的相对时间约束以及保证资源使用一致性的一致性约束，此外该模型克服了以往模型不能在应用系统的逻辑和功能部件上描述系统实时的约束的不足，允许从方法和活动上描述所需的约束，降低了单一约束描述的繁杂程度，为了能够使用现有调度算法进行任务调度，讨论了约束转换的问题，给出了高层约束到底层约束的转换规则和相应的转换算法。     

An Event-Based Approach to Spatio-Temporal Data Modeling in Land Subdivision Systems

The spatio-temporal database for a collaborative decision making system supporting land subdivision is event-driven. Both various states of spatial objects and the events causing the objects change need to be recorded and manipulated in the database. To achieve this, the authors analyzed the characteristics of events in land subdivision process and studied how events affect the states of spatial objects. An event-based approach was proposed to develop the spatio-temporal data model for the GIS-based computer-supported collaborative work (CSCW) land subdivision system. A formal specification of event and its operators was introduced for describing the execution of events and their sequence. The spatio-overlap and time-meet constraints between parent-child parcels are proposed to represent the linkage between different states of land parcels. With this approach, events and the causal relations between events and states can be recorded and managed in the spatio-temporal database in a land subdivision system. In addition, a new way for simulating system work-flow is also suggested.     

Maintaining constraints of UML models in distributed collaborative environments

Constraint maintenance plays an important role in keeping the integrity and validity of UML models in embedded software design. While constraint maintenance capabilities are reasonably adequate in existing UML modeling applications, little work has been done to address the distributed constraint maintenance issue in multi-user collaborative modeling environments. The nature of the issue is to maintain constraint consistently across distributed sites in a collaborative modeling environment in the face of concurrency. In this paper, we propose a novel solution to this issue, which can retain the effects of all concurrent modeling operations even though they may cause constraint violations. We further contribute a distributed constraint maintenance framework in which the solution is encapsulated as a generic engine that can be mounted in a variety of single-user UML modeling applications to support collaborative UML modeling and distributed constraint maintenance in embedded software design processes. This framework has been implemented in a prototype distributed collaborative UML modeling application CoRSA.     

Constraint meta-object: a new object model for distributedcollaborative designing

Object databases have been recognized as providing rich data modeling capabilities for the next-generation applications, especially CAD/CAM, software engineering, and multimedia. The core object model consisting of objects, messages and inheritance, however, is not adequate to tackle all the requirements of these applications. Since collaborative activity is one of the key features of next-generation applications, it is essential that the basic object model be extended to support collaborative activity. We propose an object model for collaborative designing based on objects and constraint meta-objects. Each design object has an associated constraint space consisting of one or more constraint meta-objects. The object/constraint meta-object separation achieves a clear distinction between design object and its associated design environment and provides a framework for supporting collaboration among members of a design team. Collaboration is modeled as dependencies among multiple constraint spaces on different nodes, and collaborative activity as design transactions satisfying local constraints and propagating constraints among interrelated constraint spaces. We propose language extensions to C++ for capturing the object/constraint meta-object paradigm. The extensions are implemented using filters, a special mechanism for capturing messages sent to an object. Our model has been applied to the case of a mechanical CAD problem     

Collaborative object-oriented visualization environment

In this paper, we present a Collaborative Object-oriented Visualization Environment (COVE) which provides a flexible and extensible framework for collaborative visualization. COVE integrates collaborative and parallel computing environments based on a distributed object model. It is built as a collection of concurrent objects: collaborative and application objects which interact with one another to construct collaborative parallel computing environments. The former enables COVE to execute various collaborative functions, while the latter allows it to execute fast parallel visualization in various modes. Also, flexibility and extensibility are provided by plugging the proper application objects into COVE at run-time, and making them interact with one another through collaboration objects. For our experiment, three visualization modes for volume rendering are designed and implemented to support the fast and flexible analysis of volume data in a collaborative environment. This work has been supported by KIPA-Information Technology Research Center, University research program by Ministry of Information & Communication, and Brain Korea 21 projects in 2005.     

Coordination Models Based on a Formal Model of Distributed Object Reflection

We propose a family of models of coordination of distributed object systems representing different views, with refinement relations between the different views. We start with distributed objects interacting via asynchronous message passing. The semantics of such a system is a set of event partial orders (event diagrams) giving the interactions during possible system executions. A global coordination requirement is a constraint on the allowed event diagrams. A system coordination specification consists of a meta-level coordinator that controls message delivery in the system according to a given global policy. The system-wide coordination can be refined/distributed using coordinators for disjoint subsystems that communicate with their peers to enforce the global policy. By a further transformation the meta-level can be replaced by systematically transformed base-level objects communicating via a controller object. The coordination models are formalized in rewriting logic using the Reflective Russian Dolls model of distributed object reflection. The general ideas are illustrated with several examples.     

Internet-enabled real-time collaborative assembly modeling via an e-Assembly system: status and promise

Collaborative CAD systems enabling collaboration in computer-aided design processes among distributed designers are gaining more and more attention. Yet, such systems, especially in support of collaborative assembly modeling, are hardly achievable. Targeting this gap, this paper addresses an Internet-enabled real-time collaborative assembly modeling system, named e-Assembly. This emerging system allows a group of geographically dispersed designers to jointly build an assembly model in real time over the Internet. In particular, this paper proposes a new assembly representation, called Collaborative Assembly Representation, for Internet-based collaborative assembly modeling. Also, collaborative assembly constraint satisfaction is addressed based on three coordination rules embedded in e-Assembly. Furthermore, the system architecture and realization of e-Assembly are provided. Finally, a prototypic implementation of e-Assembly is presented for demonstration and discussion.     

Composition and Retrieval of Visual Information for Video Databases

This paper presents a new visual aggregation model for representing visual information about moving objects in video data. Based on available automatic scene segmentation and object tracking algorithms, the proposed model provides eight operations to calculate object motions at various levels of semantic granularity. It represents trajectory, color and dimensions of a single moving object and the directional and topological relations among multiple objects over a time interval. Each representation of a motion can be normalized to improve computational cost and storage utilization. To facilitate query processing, there are two optimal approximate matching algorithms designed to match time-series visual features of moving objects. Experimental results indicate that the proposed algorithms outperform the conventional subsequence matching methods substantially in the similarity between the two trajectories. Finally, the visual aggregation model is integrated into a relational database system and a prototype content-based video retrieval system has been implemented as well.     

A graph model for mutual information based clustering

We propose a graph model for mutual information based clustering problem. This problem was originally formulated as a constrained optimization problem with respect to the conditional probability distribution of clusters. Based on the stationary distribution induced from the problem setting, we propose a function which measures the relevance among data objects under the problem setting. This function is utilized to capture the relation among data objects, and the entire objects are represented as an edge-weighted graph where pairs of objects are connected with edges with their relevance. We show that, in hard assignment, the clustering problem can be approximated as a combinatorial problem over the proposed graph model when data is uniformly distributed. By representing the data objects as a graph based on our graph model, various graph based algorithms can be utilized to solve the clustering problem over the graph. The proposed approach is evaluated on the text clustering problem over 20 Newsgroup and TREC datasets. The results are encouraging and indicate the effectiveness of our approach.     

协同语义特征建模技术研究

为了提高协同语义建模系统的性能,提出了一种新的协同设计方法,亦即使用特征语义表示法和细胞元模型来表示数据和管理模型中的各种数据和信息,然后通过语义匹配的方法来确定子模型间的逻辑和装配关系,通过语义区域划分、"最值空间"等技术来检测和消解协同设计中发生的操作冲突,最后通过创建临时模型来降低全局约束求解的复杂度。这种方法不仅能够完全实现协同语义特征建模的需要,还可以大大提高协同设计的效率。实验表明,该算法具有更强的适应性和实用性。     

A model for secure multimedia document database system in a distributed environment

The Internet provides a universal platform for large-scale distribution of information and supports inter-organizational services, system integration, and collaboration. Use of multimedia documents for dissemination and sharing of massive amounts of information is becoming a common practice for Internet-based applications and enterprises. With the rapid proliferation of multimedia data management technologies over the Internet, there is growing concern about security and privacy of information. Composing multimedia documents in a distributed heterogeneous environment involves integrating media objects from multiple security domains that may employ different access control policies for media objects. In this paper, we present a security model for distributed document management system that allows creation, storage, indexing, and presentation of secure multimedia documents. The model is based on a time augmented Petri-net and provides a flexible, multilevel access control mechanism that allows clearance-based access to different levels of information in a document. In addition, the model provides detailed multimedia synchronization requirements including deterministic and non-deterministic temporal relations and incomplete timing information among media objects.