Model Components
Model components are referred to here to mean any part of a linked model that can be interchanged i.e. ‘swopped in and out’ of a model composition.
Model components can be of many different types they need not necessarily be numerical (i.e. 3D models, functions, databases, visualisation techniques). Crucially these components can be linked together through using OpenMI via and interface called Pipistrelle.
Computational entities (e.g. climate or groundwater models) have to be made OpenMI compliant thus effectively turning them into objects, or ‘components’, and allows them to exchange data by linking the variables exposed in the interface. One of the key features of OpenMI is that a component´s owner selects which variables are exposed to, accessible by, other components. The owner can also choose the number of variables exposed.
In the future, potential exists for any component´s owner to choose what aspects of it are exposed to and accessible by other components. So, OpenMI has the potential to provide an online, secure, open-source framework of use for example in the insurance industry. It will also be possible to critique similar catastrophje models and understand the impact that changing single components will have on the modelled outputs.
Linking models with Pipistrelle
A common problem faced by natural hazard risk modellers is determining how to link different models together to represent a complete system. For example, a flood modeller might want to couple a dataset describing the geography of an area with groundwater and rainfall models to give input to a surface flooding model. Furthermore, one might want to link the surface water flow to a soil transport model, and have the soil motion feedback on the surface flow. Linking these models together even without feedback is usually a difficult task, as one might need to account for differing physical units, computational grids, ‘timesteps’ and so on.
The solution that will be used for PURE involves the OpenMI standard. Originally developed to link models in the water domain, the OpenMI provides a standard interface to allow models to exchange data with each other at runtime on a timestep-by-timestep basis. The use of a standard interface circumvents any problems that may arise from differences between suppliers, computational domains, and so on.
The OpenMI standard has already been applied successfully to several models in the water sector, and the Fluid Earth initiative has been created to provide a community based around the use of OpenMI in environmental modelling. It is the goal of the PURE Experimental Zone to create a similar community for natural hazard scientists and associated risk modellers. Furthermore, the Experimental Zone will lower the boundaries to linking models by offering a web-based interface. In essence, the Experimental Zone will contain a ‘librar’ of models and data-sources that can be linked together into a linked model (or ‘composition’) via an interface called Pipistrelle. Pipistrelle makes it easy to add, remove, or swap model components and run compositions remotely.
Pipistrelle is an application developed for HR Wallingford to help modellers create and run compositions of models that implement the OpenMI standard. Pipistrelle is available to all users of the portal via the delivery repository. Advice on installing Pipistrelle has been provided elsewhere on the portal.
Before installing, please note that Pipistrelle requires a PC running a Microsoft Windows operating system with the .NET Framework 2.0 (or above) installed.
To help modellers evaluate the benefits of Pipistrelle. This feature must first be enabled via Tools > Plugins on the task bar. A video (003_Plugins.avi) is available, which shows how to enable and use this feature. A number of other videos have also been provided, which were produced as part of the 2010 HR Wallingford FluidEarth Workshop. These videos have been made using CamStudio, and may require the user to install the CamStudio Lossless Codec (V1.4), which can be downloaded from camstudio.org. Please note that when you download these files you will need to change the .* extension to .zip.
