The Project Gallery provides a number of example projects and products based on the ACA ToolKit.

The generic information system framework consists of:

• GUI, menu system and main event loops;

• geographic information system (GIS)

• object data base including object editing and display functions

• embedded rule-based expert system

• hypertext system and embedded WWW browser;

Within this framework, using a generic client-server architecture based on the TCP/IP and the http protocol, individual information resources such as data bases and simulations models can be linked and integrated.

GUI, menu system and main event loops The information system framework is based on a fully menu driven, largely symbolic and graphical user interface. Almost all user interaction consists of point, drag, and click operations. Text input, wherever possible, uses multiple-choice selection rather than text input (typing) to minimize the potential for operator error. Menus, selections, and a range of graphical analog data entry tools (sliders, compass, etc.)

are all context sensitive and constrained to feasible ranges or choice sets to ensure consistent and plausible user input. The various icon menus and option selectors are coordinated by event loops and callbacks that translate the interactive user specifications into the appropriate actions. Consistent layout across pages, use of colors and fonts aims to simplify interpretation and learning within the system. A status bar and an embedded help- and explain hypertext system (see below) provide guidance for the novice or infrequent user.

Geographic information system (GIS) Almost all objects in the environmental information system are spatially referenced. As a major integrating tool, an embedded GIS manages these spatial data.

The GIS provides a smooth integration of different formats (vectors, graphs, rasters, cell-grids, DEMs, TINs, FE and FD model grids, dynamic model output). Its main function is to provide a spatially organized interface to the system's data objects and associated functions, as well as the display and analysis of (spatially distributed) model results.

Object data base, object editing and display functions The information system is based on an object oriented design. This approach supports the representation and structuring of the problem domain in terms of natural, real-world objects and related information requests in a format and style that is directly understandable and useful for the end user. It supports a problem (and therefor user) oriented rather than a data or model oriented view of the problem domain. Objects or object classes in this framework include:

individual functional components such as emission sources, power plants, treatment plants, observation stations, etc. related data such as observation time series or emission inventories; the individual variables or parameters that define the attributes or properties of compound objects (Descriptors in the expert systems Knowledge Base); structural and geographic elements such as road segments, city blocks or districts, hydrographical catchments, parks, etc.; tasks or decision scenarios; individual analytical tools such as simulation models.

Embedded rule-based expert system As an important generic function of the framework, an embedded rule-based expert system is used to assist the user in the definition of decision and input variables, as well as in the interpretation of results. In addition, the expert system can be used a classification tool,

for example for Environmental Impact Assessment tasks, in its own right. The expert system uses near-natural language Rules (first order logic) and as its variables Descriptors . In an interactive dialogue, the system compiles information from the user that it uses in an inference process to deduce its answers (i.e., updated attributes of objects in a changed context).

Hypertext system and embedded WWW browser The hypertext system is embedded with the overall user interface as a help- and explain function associated with information icons throught the user interface. It also provides meta-data and background information on

individual objects such as the descriptors of the expert systems, a model, or a decision scenario. In line with the distributed network architecture of the system, the hypertext browser can use both an internal hypertext format as well as with a (parallel) embedded web browser HTML documents. This supports direct access to local HTML pages as well as to the entire Internet.