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Integrative Systems Implementation Software
1 - What Is ISIS?
ISIS allows you to implement complex, dynamic systems of any structure in a hierarchical manner. It is based on the ModelWorks software (Fischlin 1991 , Fischlin et al. 1994 ) and allows for systems that can consist of any number of models of any type. For instance you can build a system which consists of several coupled ordinary differential equations (DESS - Differential Equation System Specification), difference equations (SQM - Sequential Machines), or continuous-time discrete event submodels (DEVS - Discrete Event System Specification).
ISIS supports the modeling of structured systems in a much more efficient manner than this is possible with ModelWorks:
Firstly, ISIS allows for input/output linking of modular subsystems forming larger supersystems. The subsystems can be specified independently of each other, i.e. there is no need for cross-imports of variables or model objects at the source code level. Subsystems and their objects are uniquely identified by means of identifiers (e.g., modelIdent.stateVariableIdent) and are declared to the ISIS model objects data base. ISIS then links all subsystems at run time by matching all currently declared input variables with the available output variables. The used linking technique is efficient and supports safe and correct data exchange between subsystems. Moreover, it allows for replacing whole subsystems at run time with minimum programing effort, e.g. for structural sensitivity analyses.
Secondly, ISIS allows to fully separate model data (such as the initial values of state variables, parameter values, monitoring attributes etc.) and system structure. The system structure is specified in a Modula-2 program, whereas the model data are stored separately in text files in the form of so-called data frames. These are human readable tables with a flexible, formally defined syntax. The data are automatically retrieved from the data frames and assigned to the models and their objects at run time. The data currently used in the simulation environment can be saved again to disk and stored in a data frame file for documentation or later use in a simulation experiment. ISIS is capable of extracting from a large collection of data frames precisely all data needed by the currently declared (sub-)systems. This makes it possible to flexibly use the same data frames in varying contexts, e.g. when working with different model versions that have similar data needs.
2 - Features
3 - Formal Interface
To learn about the formal interface, notably all functions of ISIS see:
4 - Availability
ISIS is freeware (courtesy ETH Zurich).
It comes as a part of the RAMSES modeling and simulation environment.
Download it for:
For information on the needed Modula-2 development environments for the various supported computer platforms see here.
5 - Authors
6 - Cited References
Fischlin, A. (1991). Interactive Modeling and Simulation of Environmental Systems on Working Stations. In: Möller, D.P.F. & Richter, O. (eds.), Analysis of dynamic systems in medicine, biology, and ecology. Informatik-Fachberichte 275: 131-145.
Fischlin, A., Gyalistras, D., Roth, O., Ulrich, M., Thöny, J. & Nemecek, T., Bugmann, H. & Thommen, F. (1994). Model Works - an interactive simulation environment for personal computers and workstations. Systems Ecology Report No. 14, ETH Zurich, Switzerland, 324pp.
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