| 摘要 |
A computer network guarantees timeliness to distributed real-time applications by allowing an application to specify its timeliness requirements and by ensuring that a data source can meet the specified requirements. A reflective memory area is established by either a data source or an application. A data source maps onto this reflective memory area and writes data into it. In order to receive data from this data source, an application requests attachment to the reflective memory area to which the data source is mapped and specifies timeliness requirements. The application may specify that it needs data either periodically or upon occurrence of some condition. The application allocates buffers at its local node to receive data. The data source then establishes a data push agent thread at its local node, and a virtual channel over the computer network between the data push agent thread and the application attached to its reflective memory area. The data push agent thread transmits data to the application over the virtual channel according to the timeliness requirements specified by the application. Such a channel-based reflective memory system simplifies data sharing and communication by utilizing the typically unidirectional pattern of data sharing and communication. For example, plant data typically is sent from a plant controller to an operator station, and control data typically is sent from an operator station to a plant controller. Additionally, a single writer, multiple reader model of communication is typically sufficient. That is, all of the data does not need to be transmitted to all of the nodes in a computer network all of the time. Thus, flexibility, switchability and scalability are provided by using channels between reader and writer groups. Scalability is provided by using channels to control data reflection and to represent the unidirectional access pattern. By using an asynchronous transfer mode network, flexibility in channel establishment and cost reduction may be achieved.
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