07 Configuring WorkFlows

Introduction

Workflows are used in DELFT-FEWS to define logical sequences of running forecast modules. The workflow itself simply defines the sequence with which the configured modules are to be run. There is no inherent information nor constraints within the workflow on the role the module has in delivering the forecasting requirement.

Workflows may contain calls to configured module instances, but may also contain calls to other workflows. In the workflowDescripors configuration described in the Regional Configuration section, the properties of the workflows is defined.

All workflows are defined in the Workflows section of the configuration; when working from a filesystem this is the WorkflowFiles directory.. Each workflow will have the same structure and must adhere to the same XML schema definition. Workflows are indentified by their name, which are registered to the system through the workflowDescriptors configuration in the Regional Configuration section.

Workflows

Workfows defined may either be available from the Workflows table -- when the configuration is loaded into the database -- or available in the WorkflowFiles directory when the configuration is available on the file system.

When available on the file system, the name of the XML file for configuring a workflow called for example ImportExternal may be:

ImportExternal 1.00 default.xml

ImportExternal               Choosen  name for this workflow.

1.00                               Version number

default                           Flag to indicate the version is the default configuration (otherwise omitted).

Each processing step in the workflow is referred to as an activity. In defining workflows, several levels of complexity in defining these activities are available;

• Simple activities
• Activities with a fallback activity;
• Activities to be run as an ensemble.

Each activity can either be a single moduleInstance of another workflow.

Figure 142 Elements of the Workflow configuration.

activity

Root element for the definition of a workflow activity. Multiple entries can be defined.

runIndependent

Boolean flag to indicate if the activity is considered to be independent of other activities in the workflows. If the flag is set to "false" (default) then the failure of this activity will casue the complete workflow being considered as having failed. No further activities will be carried out. If the flag is set to "true", then failure of an activity will not cause the workflow to fail. The next activity in the workflow will also be attempted. An indication is given to the user in the Forecast Management display if one or more workflow activities have failed.

moduleInstanceId

The ID of the moduleInstance to run as the workflow activity. This module instance must be defined in the moduleInstanceDescriptors (see Regional Configuration) and a suitable module configuration must be available (see Module configurations).

workflowId

The ID of the workflow to run as the workflow activity. This workflow must be defined in the worfklowDescriptors (see Regional Configuration) and a suitable workflow must be available (see Module configurations).

fallbackActivity

A fallback activity may be defined to run if the activity under which it is defined fails. This can be used to run a simple module if the more complex method used in preference fails, and ensures continuity of the forecasting process. The definition of the fallbackActivity is the same as the definition of an activity.

ensemble

This element is defined to indicate the activity is to run as an ensemble.

ensemble:ensembleId

Id of the ensemble to apply in retrieving data from the database. For all time series sets used as input for the activities running as an ensemble, a request for time series with this Id defined will be made. Ensemble id's in a sub workflow will override this ensembleId. A sub workflow without an ensembleId will make use of this ensembleId

ensemble:runInLoop

Boolean flag to indicate if the activity it to be run as many times are there are members in the ensemble, or if it is to be run only once, but will use all members of the ensemble in that single run. If the value is set to "true", then when running the workflow DELFT-FEWS will first establish how many members there are in the ensemble, and then run the activity for each member. If the value is set to "false" then the activity will be run only once. On requesting a time series set within the modules to be run, the database will return all members of that ensemble.

Example

<?xml version="1.0" encoding="UTF-8"?>
<workflow version="1.1" xmlns="http://www.wldelft.nl/fews" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.wldelft.nl/fews
E:\schemas\workflow.xsd">
	<activity>
		<runIndependent>false</runIndependent>
		<moduleInstanceId>Astronomical</moduleInstanceId>
	</activity>
	<activity>
		<runIndependent>true</runIndependent>
		<moduleInstanceId>BackupPrecipitation_Forecast</moduleInstanceId>
	</activity>

		<runIndependent>true</runIndependent>
		<moduleInstanceId>PrecipitationGaugeToGrid_Forecast</moduleInstanceId>
	</activity>
	<activity>
		<runIndependent>true</runIndependent>
		<moduleInstanceId>Spatial_Interpolation_Precipitation_Forecast</moduleInstanceId>
	</activity>
	<activity>
		<runIndependent>true</runIndependent>
		<moduleInstanceId>MergePrecipitation_Forecast</moduleInstanceId>
	</activity>
	<activity>
		<runIndependent>true</runIndependent>
		<moduleInstanceId>GridToCatchments_Forecast</moduleInstanceId>
	</activity>
	<activity>
		<runIndependent>true</runIndependent>
		<moduleInstanceId>Singapore_Sobek_Forecast</moduleInstanceId>
	</activity>
</workflow>