||Traffic and air quality|
SIMTRAP Systems Architecture
The SIMTRAP demonstrator is based on a client-server architecture, taking advantage of the http (hypertext transfer) protocol. The main server provides the basic user interface and controls the user dialogue, displays information, and connects to external information resources, primarily the HPC simulation models DYNEMO and DYMOS, and optionally to monitoring data and data bases.
This communication is based on the public http protocol, and can be based on
for the physical communication layer. This protocol also forms the basis of World Wide Web browsers like Mosaic or Netscape as future implementation platforms for the user interface. The following diagram summarizes this architecture:
The SIMTRAP demonstrator consists two main elements linked in this client-server system:
The SIMTRAP Server is implemented (for the purpose of the Demonstrator) on a SUN Sparc workstation under UNIX (Solaris2.5 or higher). For details, please refer to the the description of the SIMTRAP hardware and software requirements.
The MODEL Server provides:
The model server can be implemented on a dedicated parallel machine (at the GMD), or on a UNIX workstation cluster or multi-processor system (see the description of hardware requirements.
The Communication Protocol
The communication between the SIMTRAP Server and the MODEL Server is based on the TCP/IP and http protocols. Using this basic communication structure (using http POST requests for the interactive communication and a cgi script at the model server side to trigger the simulation models proper), the servers use a simple protocol based on keywords and associated values and data streams.
This protocol transfers model scenario specifications or parameters compiled and edited through the SIMTRAP Serveruser interface to the MODEL Server; results from the MODEL Server are returned through the same channel with the same protocol, using again keywords and associated values and data stream to return the computation results.
The syntax of this communication is as follows:
An example would be:
MetScenario:WorstCase EmissionNOInd:1.05 EmissionNO2Ind:1.05 EmissionVOCInd:1.05 EmissionNOHhl:1.1 EmissionNO2Hhl:1.1 EmissionVOCHhl:1.1 BackgroundVOC:1.1 NetworkScenario:Berlin2000 Weekday:Monday Specialday:Sommerferienbeginn LinkClosureFrom:100125 LinkClosureTo:100126 TrafficVolume:1.2 ...... ......
From the MODEL server , the results are sent back using basically the same conventions. The results consists of:
The model output will be structured as follows:
MetScenario:WorstCase EmissionNOInd:1.05 EmissionNO2Ind:1.05 EmissionVOCInd:1.05 EmissionNOHhl:1.1 EmissionNO2Hhl:1.1 EmissionVOCHhl:1.1 BackgroundVOC:1.1 NetworkScenario:Berlin2000 Weekday:Monday Specialday:Sommerferienbeginn LinkClosureFrom:100125 LinkClosureTo:100126 TrafficVolume:1.2 ...... ...... TimeStamp:199708040600 NumberOfCars:15 16 20 19 18 15 25 ..... (one value for each link) SpeedOfCars:40 45 48 38 40 ...... EmissionNo:100 120 110 85 110 ..... EmissionNo2:100 120 110 85 110 ..... EmissionVOC:100 120 110 85 110 ..... ConcentrationO3: 80 82 81 79 83 ....... (one value for each cell) TimeStamp:199708040615 NumberOfCars:15 16 20 19 18 15 25 ..... SpeedOfCars:40 45 48 38 40 ...... EmissionNo:100 120 110 85 110 ..... EmissionNo2:100 120 110 85 110 ..... EmissionVOC:100 120 110 85 110 ..... ConcentrationO3: 80 82 81 79 83 .......
Please note that this protocol does not include any optimization potential to minimize data transfer (server side compression, transfer of deltas, etc.) is is purely designed to simplify the initial server integration and the debugging of the data transfer.
Input ParametersInput parameters specified in the user interface are always presented as a list of options the user can chose from. Parameter values can
Distributed Data Bases
The data bases for the SIMTRAP system are distributed between the SIMTRAP server and the MODEL server. By default, all model input data are stored with and managed by, the MODEL server. Since the SIMTRAP servers user interface does not support access to ALL the model input, but only those that are considered:
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