Multimedia Tools for
Advanced GIS Training in Europe

The MUTATE project is funded by the Educational Multimedia Task Force of the European Union.

MUTATE Educational Multimedia Project MM1019 (ET):
Internal Deliverable D3.2

Client-Server Architecture

systems architecture, networking, client-server, HPCN, http, environmental modeling, spatial analysis, air quality,
Release January 1999
Author: Kurt Fedra

Programme name Educational Multimedia
Project Acronym MUTATE
Contract number MM 1019 (ET)
Project title MUltimedia Tools for Advanced gis Training in Europe
Deliverable number ID3.2
Deliverable title Client-Server Architecture
Deliverable version number 1.1
Work package WP3 (Development and integration of complex dynamic simulation models and sptial DSS
Nature of the deliverable Online Multimedia component
Dissemination level Limited to Programme Participants
Contractual date of delivery PM6 (June 1998)
Actual date of delivery PM13 (online)
January 1999
Author Dr.Kurt Fedra
Environmental Software & Services GmbH
Kalkgewerk 1   PO Box 100
A-2352 Gumpoldskirchen, AUSTRIA
tel: +43 2252 633 05
fax: +43 2252 633 059
Project technical co-ordinator Dr.Joao Ribeiro da Costa, Chiron - Sistemas de Informacao, Lda.
tel: +351 1 3500 278
fax: +351 1 2943 710

Client-Server Architecure

Executive Summary

This deliverable contains, as a hyperlinked on-line Multimedia document, a summary description of the client-server architecture of the interactive dynamic modeling components. Its objective is to docuemnt the basic architecture as well as its actual implementation within the MUTATE project.

The Deliverable

  • describes the basic client-server architecture

  • includes a short introduction to tools and standards used (TCP/IP, http, cgi) for the client server integration of the MUTATE modeling components;
  • provide a summary documentation of the client-server protocol and the data structures generated for post-processing and display.

As an on-line working document, it is being updated periodically to reflect progress in WP 3, and be linked to the other Deliverables in the D3 group as they become available.

The client-server architecture is based on the standard protocols TCP/IP and http; it uses a central server that can be remote or integrated with the basic MUTATE server, and is accessible from the remote clients either from normal HTML pages or a Java Applet. HTML pages re using the POST protocol to communicate the parameter lists for a request to the server (a model run or rendering a map). The model server is triggerec by the cgi (Common Gateway Interface) method.

The results of the model server are then sent back to the client browser (applet or HTML page) for interpretation. In addition, at the server site a file copy of the results is stored that can be downloaded by the client using standard protocols such as the ftp File Transfer Protocol for subsequent local post-processing of the result files.

Structure of the Deliverable

The main page of the Deliverable ( contains the Executive Summary, and a short description of the client-server architecture.

Client-Server Architecure

MUTATE environmental modeling tools developed and implemented by ESS are based on a generic client-server architecture that combines a powerful model server for high-performance computations required for interactive modeling with the flexibility of a Java based user interface.

The models are run on a (conceptual) model server, that is linked to the main MUTATE http server either on a local area network (LAN) or on the same (multi-tasking) UNIX machine; a bandwidth of 100 Mb/s (at least 10 Mb/s) provided by fast Ethernet is recommended.

The client software (Java applets triggered within a standard web browser) is platform independent and can be run on any client hardware such as PCs or workstations, including light-weight low-end PCs.

The client software performs two major groups of interactive interface functions:

  • definition of simulation scenarios;
  • display and rendering of model results.

Using the Model Server

For the integration of the MUTATE Model Server into the courses of the MUTATE Bundle, several communication and integration mechanisms are foreseen:
  • individual calls to the model server from XML/HTML pages; a complete set of scenario specifications is sent to the Model Server cgi (Post request);
    the model server returns its results in graphical format (GIF, PNG); this may consist of the model results (in different graphical renderings) with or without background maps, or possibly specific graphs derived from the primary model results;

  • output files deposited by the model server in a standard directory; the primary output of the simulation models are cell-grid files with scalar or vector data;

  • media player a separate interface that provides access to all the model functions; here the caller can specify a parameter mask that defines a (sub)set of parameters for user editing. The media player provides its own interface for the display of model results, and has an (optional) data export function (see above).

Check the detailed description of communication protocol and file formtas for the client-server communication.

Conceptual architecture

From a didactic perspective, the models are designed for scenario analysis or experimentation, where each scenario or experiment in turn should be designed to illustrate one or several basic concepts within the framework of a course module.

The scenario here is defined as a complete set of initial and boundary conditions for a given model, plus the results of running the model with these inputs.

For a given exercise or illustration, most of these parameters will be fixed at predefined values, but a few will be open (within well defined ranges) to be changed by the student interactively to explore the concept of the lesson.

The underlying experiments a student can perform will therefor be of one of two types:

  • WHAT IF:   here a set of parameters or ranges for parameter changes are given, the student is asked to explore (and possibly to predict and then verify experimentally) their effect on systems behaviour;

    A typical example could be the relationship between (atmospheric) dispersion parameters and the spatial distribution of pollutant concentration from one or several emission sources.

  • HOW TO:   here a desired system state is given as the starting point, the student is asked to find (describe and subsequently verify experimentally) the parameter settings that will result in this target state.

    A typical example could be a (spatial) environmental quality standard as the target, and emission reduction options as the decision variables.

    In the latter case, the student's experimental approach could also be checked against an optimization routine.

Scenario Analysis

In the example case of the Air Quality simulation system AirWare, a standard simulation scenario for major industrial point sources and for the simplest possible (steady-state) models, consists of the following elements:

1) Model Scenario

The model scenario involves the selection and definition of the following items:

  • choice of model (ISC-2, ISC-3 (with or without COMPLEX domain corrections; please note that the domain corrections require that a DEM is available for the model domain)

  • choice of simulation period (please note that this is related to the choice of models, since not all models are available in both a short-term (episode or event) and long-term (seasonal, yearly) version.

  • choice of spatial resolution (grid size).

2) Emission Scenario

The emission scenario involves the selection of one of the pre-defined emission inventories, and, on this basis, the definition of a set of emission sources. This includes:

  • selection of sources;

  • positioning of sources;

  • definition of source parameters; for an (industrial) point source, this includes:

    • emission rate for each substance under consideration; Please note that in case of particulates, this also includes the specification of a particle size (distribution) and specific gravity;

    • stack height

    • stack diameter

    • flue gas temperature

    • exit velocity.

3) Weather Scenario

The content of a weather scenario depends on the choice of model (see above) and the temporal resolution and duration of the simulation.

For a short-term (episode) model run, typically for a one-hour averaging period:

  • wind speed (including the measurement stations reference height);

  • wind direction

  • air temperature

  • mixing height

  • stability class.

For a long-term seasonal or annual model run, frequency distributions for the above variables are required. In AirWare, they are generated automatically given the selection of a meteorological station, and the definition of the start- and end-dates of the desired simulation period.

4) Display/Analysis Scenario

The display scenario includes:

  • selection of a sub-domain (zooming, panning)
  • selection of color ramp and classification/display boundaries
  • selection of display styles (translucent or opaque, original grid or smoothed, isolines, 3D representation)

Copyright 1995-2002 by:   ESS   Environmental Software and Services GmbH AUSTRIA