FAQs Related to Development of FEWS Adapter

The model adapter as described in this manual provides the interface between a so-called model and the Delft-FEWS system. It enables FEWS to run such a model, thus providing the essential forecasting functionality. For each particular FEWS application applying a model, however, some aspects of this system have to be configured by the user in order for the system to work correctly. To achieve this, it is useful that the user has at least some basic understanding of the relation between Delft-FEWS, the model adapter and the forecasting model. In this section, a brief overview of this relation is provided. For more information, the user is referred to the FEWS manual: General Adapter.

Delft-FEWS and the general adapter

A key feature of DELFT-FEWS is its ability to run external modules to provide essential forecasting functionality. The General Adapter is the part of the DELFT-FEWS system that implements this feature. It is responsible for the data exchange with these modules and for executing the modules and their adapters. The Delft3D model adapter is an example of such a module run from the General Adapter (see also FEWS manual: General Adapter).

In order to develop a model adpater for a FEWS application, it is important to have a clear understanding of the relation between the General Adapter and a model adapter. This section summarizes some of the functionalities included in the FEWS general adapter module, and their relation to a model adapter.

The schematic interaction between the general adapter and an external moduleis shown in the below figure.

Figure 1: schematic interaction between the FEWS and an external module

This figure is understood in the following way:

1. The general adapter is that part of DELFT-FEWS which exports model input, imports model output data, and executes the pre-adapter, module and post-adapter.
2. Export and import of model data is done in datafiles following the Published Interface (PI) XML format.
3. The preAdapter, Module and postAdapter together form the model adapter. The model adapter is initiated from the general adapter.
4. The preAdapter is that part of the model adapter which converts input data in PI XML format to native model input data.
5. The postAdapter is that part of the model adapter which converts native model output data to PI XML format to be imported by FEWS.
6. The Module is that part of the model adapter which starts a model simulation.

Essential in this division of tasks between model adapter and general adapter is that from the vantage point of the general adapter the model adapter is a black box, and visa-versa. Exchange of information between these components is done based on exchange of PI XML data files; DELFT-FEWS does not have any knowledge about the modelling system (Delft3D in this case), whereas the modelling system does not have any knowledge about DELFT-FEWS. Translation of data from one component to the other is done using the model adapter. Thus model adapter is not a part of the Delft-FEWS system itself, but is essentially an external program initiated by DELFT-FEWS through the general adapter. In other words, for Delft-FEWS system a model adapter(s) + model is a model itself which read PI XML files as input and writes PI XML files as output.

This external program (the model adapter) should provide all the functionalities to, i) convert specific PI XML data to specific native model input files and model state ii) initiate a model simulation and iii) convert model output data and end state to PI XML data readable by DELFT-FEWS. In addition, this model adapter has the following tasks, iv) logging of errors during all steps by the model adapter and by the model itself and v) administation of the model state. For both these tasks pre-defined PI XML file formats exists readable by DELFT-FEWS.

The model adapter should be as far as possible made configurable and must be done in a consistent way.

Please see the PI Documentation