This paper discusses Cova, a novel programming language designed to develop integra-tive cooperative applications and the issues related to the design and implementation of its runtime system.
A cooperative platform called Cova is presented, which aims to uniformly model a wide range of cooperation scenarios and to reduce the groupware design and development work. To achieve these goals, Cova provides two f...A cooperative platform called Cova is presented, which aims to uniformly model a wide range of cooperation scenarios and to reduce the groupware design and development work. To achieve these goals, Cova provides two facilities, namely a specification language for developers to describe various cooperation modes uniformly and a run-time system that provides some generalpurposed services guaranteeing the semantics specified. With these facilities, the developers can then concentrate on the application specific functions rather than the control mechanisms. Therefore, the development efficiency is promoted. This paper details the design and implementation issues of the platform including the model and the specification language, platform architecture,transaction management, service integration and so on. Application development with Cova platform is also covered.展开更多
Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexibl...Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexible human-to-computer and human-to-human interactions while maintaining the consistency of the system. This paper summarizes previ- ous researches on this topic and points out the deficiencies of the existing results. A novel semantics-based concurrency control framework, oodOPT is proposed. The main idea of the framework is to resolve conflicts by utilizing semantics of the operations and the accessed data objects. With this approach, complexities in concurrency control are shifted completely from application developers to the framework. Conflicts among operations on objects with different semantics and the strategies resolving these conflicts are analyzed. After describing the algo- rithm in full detail, the discussion ends up with a comparison with other related work and some considerations for open problems.展开更多
To understand the seasonal variations of water use efficiency (WUE) of coniferous plantation in the subtropical monsoon area, the experiment was conducted in 2003 and 2004 which presented two distinguished climatic co...To understand the seasonal variations of water use efficiency (WUE) of coniferous plantation in the subtropical monsoon area, the experiment was conducted in 2003 and 2004 which presented two distinguished climatic conditions (severe summer drought in 2003 and normal climatic condition in 2004). The water stress influenced WUE greatly, which caused a special seasonal WUE pattern. WUE reached the minimum in summer drought and the maximum in winter, which was contrary to the variation of gross primary production (GPP) and canopy evaporation (Fw). In winter, GPP and Fw increased along with the increasing of air temperature and vapor pressure deficit (VPD), with the similar increasing rate. However, in drought summer, there was an adverse trend among GPP/Fw and air temperature and VPD, and the decreasing rate of GPP was far larger than that of Fw. In summer, the conservation of WUE was changed because of the environmental factors, resulting in the decreasing WUE. The photosynthesis and transpiration of vegetation were mainly controlled by the environmental factors in winter, and the impact of stomatal regulation was relatively weak. In summer, Fw was mainly controlled by the stomatal closure and GPP by both environmental factors and stomatal closure.展开更多
基金the National Natural Science Foundation of China (Grant No. 269773029) National High-Tech Research and Development Plan under contract No. 863-306-ZD-10-2B and 863-306-ZD-02-03-1.
文摘This paper discusses Cova, a novel programming language designed to develop integra-tive cooperative applications and the issues related to the design and implementation of its runtime system.
文摘A cooperative platform called Cova is presented, which aims to uniformly model a wide range of cooperation scenarios and to reduce the groupware design and development work. To achieve these goals, Cova provides two facilities, namely a specification language for developers to describe various cooperation modes uniformly and a run-time system that provides some generalpurposed services guaranteeing the semantics specified. With these facilities, the developers can then concentrate on the application specific functions rather than the control mechanisms. Therefore, the development efficiency is promoted. This paper details the design and implementation issues of the platform including the model and the specification language, platform architecture,transaction management, service integration and so on. Application development with Cova platform is also covered.
基金The work was supported by the National Natural Science Foundation of China under grant No.69773029 and theNational '863' High-
文摘Concurrency control has always been one of the most important issues in the design of synchronous groupware systems with fully-replicated architecture. An ideal strate- gy should be able to support natural and flexible human-to-computer and human-to-human interactions while maintaining the consistency of the system. This paper summarizes previ- ous researches on this topic and points out the deficiencies of the existing results. A novel semantics-based concurrency control framework, oodOPT is proposed. The main idea of the framework is to resolve conflicts by utilizing semantics of the operations and the accessed data objects. With this approach, complexities in concurrency control are shifted completely from application developers to the framework. Conflicts among operations on objects with different semantics and the strategies resolving these conflicts are analyzed. After describing the algo- rithm in full detail, the discussion ends up with a comparison with other related work and some considerations for open problems.
基金This work was supported by the Na-tional Outstanding Young Scientists Foundation of China (Grant No. 30225012) the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX1-SW01-01A)+1 种基金 the National Basic Research Program of China (Grant No 2002CB412501) the Asia-Pacific Environ-mental Innovation Strategy Project (APEIS).
文摘To understand the seasonal variations of water use efficiency (WUE) of coniferous plantation in the subtropical monsoon area, the experiment was conducted in 2003 and 2004 which presented two distinguished climatic conditions (severe summer drought in 2003 and normal climatic condition in 2004). The water stress influenced WUE greatly, which caused a special seasonal WUE pattern. WUE reached the minimum in summer drought and the maximum in winter, which was contrary to the variation of gross primary production (GPP) and canopy evaporation (Fw). In winter, GPP and Fw increased along with the increasing of air temperature and vapor pressure deficit (VPD), with the similar increasing rate. However, in drought summer, there was an adverse trend among GPP/Fw and air temperature and VPD, and the decreasing rate of GPP was far larger than that of Fw. In summer, the conservation of WUE was changed because of the environmental factors, resulting in the decreasing WUE. The photosynthesis and transpiration of vegetation were mainly controlled by the environmental factors in winter, and the impact of stomatal regulation was relatively weak. In summer, Fw was mainly controlled by the stomatal closure and GPP by both environmental factors and stomatal closure.
