1. Introduction
Although it may appear a huge challenge to turn a model engine code (the computational heart of a model) into an OpenMI-compliant linkable component, it may not be as difficult as it seems. The OpenMI Software Development Kit (SDK) provides a large number of software utilities that make migration easier. These utilities can be used by anyone migrating a model but are not required in order to comply with the OpenMI standard. The SDK can be used as a whole or you can select only part of it; alternatively, you can use the SDK as the basis for your own implementations. This article assumes that you will use the OpenMI SDK to the full extent. Step-by-step instructions are given for the whole migration process, from defining the requirements for an OpenMI component, through design and implementation to testing. |
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1.1. OpenMI compliance
The official requirements for OpenMI compliance are:
There are two variants of OpenMI compliance. Component can be either OpenMI 1.4 .Net compliant or OpenMI 1.4 Java Compliant.
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However, when you use the software development kit provided by the OpenMI Association Technical Committee (Oatc.OpenMI.Sdk) most of the requirements for compliance will automatically be taken care of.
1.2. The simple river example
A Simple River model engine was developed as an example of model migration. The model engine is programmed in Fortran and is a very simple conceptual river model. The Simple River consists of nodes and branches, as shown in Figure 1. For each timestep, the inflow to each node is obtained from a boundary-input file. These flow rates are multiplied by the timestep length and added to the storage in each node. Then, starting from the upstream end, the water is moved to downstream nodes and the flow rate in each branch is calculated.
Source code for the Simple River model (FORTRAN engine and C# wrapper) is included in the OpenMI 1.4.0.0 SDK release, which can be downloaded from: http://sourceforge.net/projects/openmi/
Fig 1. Simple River network
The Simple River engine reads data from three input files, which contain information about the inflow to the river nodes (boundary file), the simulation period and timestep length (simulation file) and the river network (network file) - see Figure 2.
Fig 2. Simple River input and output files
