RiverSMART is included as part of the RiverWare installation. Install RiverWare and RiverSMART will be installed in the same location as RiverWare.

To start RiverSMART, use the desktop shortcut icon or locate RiverSMART.exe in the installation folder and double click to start it:

When you start a new RiverSMART study, you must assign a study name and the Study Folder, which is the folder where the study and all its subfolders are written. Environment variables can be used in the Study Folder path; if used, they must be preceded by a $ symbol.

The File menu includes options for saving the study, opening an existing study, and exiting RiverSMART.

The RiverSMART Help item on the Help menu displays this Help document.

The Help button in the toolbar also opens the RiverSMART Help.

An important aspect of RiverSMART is its ability to manage all files associated with a complex study. The Study Folder, which you specify when you create a study, is the root for all subfolders and files; see “Installing and Starting RiverSMART” for details.

RiverSMART automatically creates the following folders under the Study Folder. This self-contained folder structure makes it easy to archive or move the entire study.

The RiverSMART workspace is populated with events, files, and links to create a study. These study building blocks are discussed in the following sections.

RiverSMART is essentially a framework for communication between independent processes or programs, which are called events. On the software level, each event is actually an independent program called a plugin, and an event is an instance of a plugin.

To add an event to the workspace, right-click the workspace; in the shortcut menu, select Add Event and then the event you want to add.

When an event is added to the workspace, it is shown as an icon representing the event type. Following are descriptions of the available events, categorized by function.

Hydrology events allow you to create traces of hydrology data that can be moved into RiverWare through a specified RiverWare Data Management Interface (DMI) event.

Input events allow you to configure inputs to the model and options for generating scenarios.

Post-processing events allow you to configure options for processing study results.

To open the Configuration dialog box for an event, double-click the event icon on the RiverSMART workspace. Following is a sample Configuration dialog box for a RiverWare DMI event.

File items specify file names for outputs from events. When linked to a following event, a file item specifies an input file name for that event.

To add a file to the RiverSMART workspace, right-click the workspace, select Add File on the shortcut menu, and then select the file type. The following file types are available.

To open the Configuration dialog box for a file, open the file icon on the RiverSMART workspace. Following is a sample Configuration dialog box for an RDF file.

You create links on the workspace to represent how information flows between events and files. The link arrow indicates the direction of the link.

In some cases, you can link an event directly to another event; but in cases where the event output is preserved as a file, you can link the event to a file item, which can then be linked to a following event. Hydrology events link directly to each other; RiverWare input events link directly to RiverWare; and post-processing events link through file items.

To create a link, right-click an event or file, select Link in the shortcut menu, and then use one of the following methods.

To delete a link, right-click the link line and select Delete Link in the shortcut menu; alternatively, select the line and press Delete.

You can add text to the workspace to identify items that can be grouped together, or to add other information.

To add text, right-click the desired location on the workspace and select Add Text in the shortcut menu. Enter the desired information in the text configuration dialog box. Line beaks will be respected. Click OK to close the Text Configuration. You can drag the text to any location on the workspace. To edit the text, double click to open the text box. To delete the text, right-click the text box and select Delete Text in the shortcut menu; alternatively, select the text and press Delete.

You can select one or more text items and use the controls in the workspace toolbar to modify their color and font size. Any new text added to the workspace uses the font size and color selected in the toolbar.

Use one of the following methods to select multiple events, files, or text items.

When you right-click the selected items, the shortcut menu applies to all selected items.

You can copy selected events, files, and text items to the system clipboard, and then paste them anywhere in the current study. The spatial relationships among the selected items are preserved, as are any links.

To copy items to the system clipboard, right-click the selected items and select Copy from the shortcut menu. The exact wording of the Copy option varies according to the selected items.

To paste items from the system clipboard to the current study, right-click the workspace and select one of the following options from the shortcut menu.

After you paste the items, they remain selected so you can adjust their placement.

You can also copy and paste items to and from external applications that support the system clipboard; for example, text editors and email clients.

The File menu in the RiverSMART menu bar includes menu items to open and save study files. The Reopen Study menu lists the six most recently opened study files and folders.

You can select files and folders by selecting them on the menu or by entering their number. Selecting a file opens the study file, and selecting a folder opens the File Chooser in the folder.

The RiverSMART Workspace menu includes options for controlling the collection and display of diagnostic messages, validating the configurations of the events and files in the workspace, and clearing the workspace.

Diagnostic messages are displayed in the RiverSMART Diagnostics dialog box, and they are color-coded as follows:

The Diagnostics File and Edit menus include options to save diagnostic messages to a file, copy diagnostic messages to the system clipboard, and clear all diagnostic messages.

The Validate Study option on the Workspace menu validates the configurations of the events and files shown on the workspace. Validation varies with the event or file, but generally includes verifying that required configuration information is provided and that referenced files that should already exist are available and readable.

Validation messages are displayed in the Study Validation dialog box, and they use the same color coding as diagnostic messages.

The Study Validation File and Edit menus provide the same options as the Diagnostics dialog box.

The Study Validation Column menu hides or shows the Type column.

The Clear Workspace option on the Workspace menu removes all events, files, links, and text from the workspace.

Controls on the toolbar allow you to zoom in and out of the workspace in increments of 10 percent, within the range of 10%–400%. The current zoom percent is displayed next to the controls.

The size and location of the four scenario dialog boxes—confirmation, organization, simulation, and post-processing—are saved so they always open using the same size and placement on the workspace. This geometry persists across RiverSMART sessions.

To reset the window geometry to the default settings, select Workspace, then Options; alternatively, select the Options button on the RiverSMART toolbar.

In the Group area of the Options dialog box, select Windowing, then Geometry. Under Reset the Following, select the Scenario Window Geometry check box, then select Reset.

The Status Bar, near the bottom of the workspace, includes the following elements.

Figure 2.1 is a sample configured workspace with events, files, and links. This example study shows two sets of hydrology events, which are linked in the upper-right portion of the workspace.

Only one RiverWare event is allowed in a study. In the example, RiverWare inputs are linked to RiverWare, on the left side of the workspace, with DMIs grouped into Demands, Supplies, and Evap. RDF files coming out of RiverWare are post-processed through a series of events and files, on the right side of the workspace, to produce GPAT graphs in Excel workbooks.

When you configure a study, you must consider what to configure in the RiverWare model versus what to configure as inputs in RiverSMART. This is particularly true for MRM and DMI configurations.

MRM configurations in RiverWare can specify initialization and per-trace DMIs, as well as policy. One approach is to create a RiverSMART event for a RiverWare MRM configuration that includes these components and not include the DMIs and policy as events on the RiverSMART workspace. This hides the scenario components, however, and prevents them from being displayed in RiverSMART. To view the DMIs and policies, you need to open the RiverWare model, which reduces the usefulness of RiverSMART for visualizing how inputs are combined into scenarios.

A more transparent approach is to create DMI and policy events in RiverSMART to be paired with an MRM configuration event. RiverWare substitutes the DMIs and policy configured in the RiverSMART events into the MRM configuration to create the scenarios. In this approach, the RiverSMART workspace provides a visual representation of how the scenario components are combined into scenarios.

As an example of DMI configuration trade-offs, consider the four demand DMIs in Figure 2.1. These could be Excel Database DMIs, in which the data for each demand is included on a separate worksheet in an Excel workbook.

One approach would be to set up four DMIs in RiverWare and have each DMI event in RiverSMART refer to one of the RiverWare DMIs by name. To set up the DMIs in RiverWare, you would need to repeat much of the same configuration information four separate times: you would need to repeat the Excel dataset configurations, each of which specify a different worksheet in the same Excel workbook, for each DMI; more importantly, you would need to repeat the slots into which the demand data is imported. This would involve possibly hundreds of slots, and it would be a tedious and error-prone process to keep their begin dates, end dates, and units consistent across all DMIs. Figure 2.2 shows a sample RiverWare configuration of an Excel Database DMI with slot selections.

A better approach is to create one dataset and one DMI in RiverWare, to serve as a template for RiverSMART to use for each scenario. You can configure the Excel dataset to refer to the Excel workbook, leaving the Single Run Name (worksheet name) blank, as shown in the following figure.

The RiverWare DMI then uses this template dataset, including the slot selections shown in Figure 2.2. The four RiverSMART DMI events refer to the RiverWare DMI, but each specify a different worksheet name to be substituted into the template dataset for that particular demand, as shown in the following figure.

Using this approach, you need to maintain just one dataset and one DMI in RiverWare. RiverSMART can use these as a template and substitute the correct worksheet for each demand as configured in its DMI events. A disadvantage of this approach is that you cannot run the demand DMIs interactively from RiverWare without inserting the missing information into the template manually or through a script.

The hydrology-related events link to one another, but not to other types of events. Their purpose is to create traces of hydrology data that can be moved into RiverWare through a separately configured RiverWare DMI event. Generating hydrologies can be time-consuming, and once configured properly, these events are not typically rerun unless some input data has changed.

To execute a hydrology event, right-click the event and select one of the execution options from the shortcut menu. You can execute just the selected event, all previous linked events up to and including the selected event, or all events after the selected event. These options provide flexibility for executing a linked hydrology sequence, allowing you to rerun just the parts you need.

RiverSMART saves all generated hydrology results to the Study Folder you have specified, using the following structure.

A scenario is a specific combination of RiverWare inputs that create a RiverWare run. The generation, simulation, and post-processing of RiverWare scenarios are controlled from the Scenarios menu in RiverSMART.

The Scenario List Organizer dialog box allows you to define scenarios from all potential combinations of inputs linked to RiverWare. To open this dialog box, select Scenarios, then Generate Scenarios on the RiverSMART menu.

A column is created for each RiverWare input category. In the example, the RiverWare DMIs have been assigned one of three category names in their configuration dialog boxes, so these categories show up as separate columns: Supply, Demand, and Evap.

The scenario name is automatically formed by concatenating the column names from left to right. By default, the columns are displayed in alphabetical order, but you can drag them into any order that is useful for identifying the scenarios.

You can make additional changes to scenario names by selecting Edit, then Scenario Name Configuration.

The Scenario Name Configuration dialog box allows you to select the columns to include in the scenario name. It also allows you to define the separator between the components.

In this example, the same MRM Configuration and Model are used for all scenarios, so including them in the name adds no meaningful information to help differentiate among scenarios. The check boxes for these elements are therefore cleared to exclude them from the name. A comma is selected as the separator in the Components Are Separated By menu. An example scenario name is displayed at the bottom of the dialog box.

The Scenario List Organizer indicates that 48 scenarios have been created from the combination of inputs to RiverWare. Not all of these combinations are meaningful, however—for example, VIC Evap should only be used with VIC supplies. Only 12 scenarios among the 48 should be run for this model.

To eliminate unwanted combinations from all dialog boxes, you can select the unwanted scenarios and deactivate them. To select scenarios, select Check and then one of the following options:

Once you have selected unwanted scenarios, you can deactivate them by selecting Edit, then Deactivate Checked Scenarios. When a scenario is deactivated, it is made unavailable throughout RiverSMART and is not displayed in any RiverSMART dialog boxes.

If you deactivate a scenario by mistake, you can reactivate all scenarios by selecting Edit, then Activate Inactive Scenarios. You can then select the correct ones and deactivate them.

You can also dynamically hide and show active scenarios in the current dialog box. Hiding a scenario does not deactivate it; it simply hides the scenario in the current dialog box and does not affect other dialog boxes.

To hide active scenarios, select the rows, then select View, then Hide Checked Scenarios. To show all active scenarios, select View, then Show Hidden Scenarios.

The status line at the bottom of the dialog box displays the number of scenarios active, shown, hidden, and currently selected.

The Scenario List Simulator dialog box displays a two-level tree view that lists the activated scenarios at the top level. Within each scenario, the activities that have been completed during simulation are listed. To open this dialog box, select Scenarios, then Simulate Scenarios on the RiverSMART menu.

To initiate a RiverWare MRM run using the scenario inputs, select the scenario check box, and then select Scenarios, then Simulate Checked Scenarios.

MRM runs are typically set up as distributed runs. If they are not set up that way, they are automatically converted into distributed runs using the default number of processors on the machine. If you select more than one scenario in the Scenario List Simulator, each one runs sequentially until all are completed.

If you need to halt execution while scenarios are running, select Scenarios, then Stop Simulations. The current scenario is allowed to finish, and subsequent scenarios are prevented from executing before they start.

During simulation, the RiverWare Distributed MRM window is displayed. This window displays the progress of the runs as follows:

Additional information on use of iterative MRM is in “Using Iterative MRM configurations”.

For any type of simulation, if you need to interrupt a scenario while it is running, select Stop All.

The Scenario List Simulator window displays detailed information for each scenario simulation.

If a scenario simulation is successful, the Run icon changes from gray to green. If a simulation is not successful, the Run icon turns red. A check mark indicates the simulation succeeded. If the check mark is orange, the simulation succeeded with a warning.

When you select a scenario, the status line displays the current status information for that scenario, including any warning messages, if applicable.

The simulation success or failure status is saved with the study and is displayed when the study is reopened.

You can manually override the Run icon color by selecting Scenarios, then Mark Checked Scenarios As Simulated or Mark Checked Scenarios As Not Simulated. For example, if a scenario simulation is successful, but the study is not saved afterward, the Run icon is gray when the study is reopened. You can correct this by manually setting the Run icon green.

If you select the File Folder icon at the end of a scenario row, a Windows Explorer window opens to the folder where the generated files for the scenario are located.

When a scenario tree view is expanded, the activities for a simulated scenario are displayed. An activity represents a step in the scenario simulation, such as initializing the model, executing the distributed MRM controller, or simulating traces. A green check mark indicates the activity was successful; a red check mark indicates the activity failed, and an orange check mark indicates the simulation succeeded with a warning. Selecting the simulation displays the warning.

CADSWES recommends expanding the activity lists for simulated scenarios and reviewing the activity details for any issues. When you select an activity, its status is displayed in the status area of the window. If RiverWare generated a log file for the activity, the File icon in the status message is enabled and you can select it to open the log file for viewing. This may be useful in troubleshooting issues for failed RiverWare activities. The following figure shows traces that have failed.

When a scenario simulation is run, keyword/value descriptors are created to characterize the scenario and its input events. These descriptors are written to the MRM configuration in the RiverWare distributed model as MRM descriptors. From there, they are optionally available as outputs to CSV and netCDF files from the multiple run. Descriptor keyword/value pairs are created as follows:

The Scenario List Simulator window also provides options to deactivate or activate, and dynamically hide or show scenarios. These options function in the same manner as those on the Scenario List Organizer dialog box.

Deactivating a scenario makes it unavailable throughout RiverSMART and removes it from all RiverSMART dialog boxes. To deactivate scenarios, select the scenarios, and then select Edit, then Deactivate Checked Scenarios. To activate all inactive scenarios, select Edit, then Activate Inactive Scenarios.

Hiding a scenario does not deactivate it; it simply hides the scenario in the current dialog box and does not affect other dialog boxes. If many scenarios have run successfully, you may want to hide them to reduce clutter on the workspace. To hide active scenarios, select the scenarios, and then select View, then Hide Checked Scenarios. To show all active scenarios, select View, then Show Hidden Scenarios.

RiverSMART saves all scenario simulation results to the Study Folder you have specified, using the following structure.

Scenario outputs (RDF, CSV, NetCDF, Excel, and R Script output files) can be archived as ZIP files in user-specified archive folder. Archiving is useful if you want to conserve disk space or share outputs.

To configure archiving, select Workspace, then Options from the RiverSMART menu; alternatively, select the Options button on the RiverSMART toolbar.

In the Group area of the Options dialog box, select Archiving to configure when and how to archive successful scenarios.

When scenarios are generated, simulated, or post-processed, the scenario order is determined by the order of the RiverWare inputs, with the leftmost input changing least frequently, and the rightmost input changing most frequently.

By default, scenarios are displayed in ascending alphabetical order, as shown in the following figure.

To display scenarios in descending alphabetical order, select Descending Z-A.

To display scenarios in a custom order, select Custom, then use the Up and Down arrows to move selected scenarios up and down one row at a time.

When input events (DMI, MRM, Model, or Policy) are modified, RiverSMART provides visual indicators to identify portions of the study that are out of date. If any item in an input event configuration dialog box is modified, other than the name, the event label turns red to indicate that scenarios in which the event is included must be regenerated.

If a new input event is added to the study, its label is also red, indicating that scenarios must be regenerated to incorporate the new event.

You can also manually indicate that an input event has been modified. This is useful when external files, such as a ruleset or data files, are modified, because RiverSMART is not aware of these changes. To indicate that an event has been modified, select Edit, then Externally Modified in the event configuration dialog box. This has the same effect as modifying the event configuration: the event label turns red, and RiverSMART indicates that scenarios in which the event is included must be regenerated to bring the study up to date.

As an additional indication that scenarios may be out of date, in the Scenario List Simulator and Scenario List Post-Processor dialog boxes, any scenario that includes a modified event is displayed in red text. Scenarios not affected by changes to input events remain black.

To update all scenarios that have had input events modified, you must regenerate scenarios. On the RiverSMART menu, select Scenario, then Regenerate Scenarios.

The Scenario Confirmation dialog box opens, listing the number of scenarios to be added, removed, invalidated, or unaffected, based on modifications made to input events since the last time scenarios were generated. To expand a row and list the scenarios in that category, select the arrow next to the row.

Each category description includes the number of inactive scenarios. To display inactive scenarios, select the Show inactive scenarios check box. Inactive scenarios are shown as unavailable (dimmed).

The Scenario Confirmation dialog box includes information to assist you in making informed decisions about regenerating scenarios.

The following discussion relates to the example in Figure 2.3.

In the example, pink highlights indicate scenarios to be removed, and green highlights indicate scenarios to be added. Out-of-date scenarios, whose results will be invalidated, are highlighted to indicate the input events that caused them to be out of date.

Green Run status icons identify the scenarios that have been successfully simulated. Removing these scenarios or invalidating their results could represent a loss of significant time and effort, and the simulation status informs you of this potential loss.

You can modify some input events to add scenarios without invalidating existing ones. For example, in the DMI Sequence event, extending the sequence adds scenarios without invalidating existing scenarios; however, because of the way it generates scenarios, RiverSMART cannot recognize the distinction and therefore includes the existing scenarios with the ones whose results will be invalidated.

In this example, the “InitCond” DMI sequence event was modified to add scenarios with initial condition “Borg02”. This causes scenarios with initial condition “Borg01” to be out of date. The user removed the check from the box for the “Baseline\Borg01” scenarios to preserve their results, which eliminates the need to re-simulate those scenarios. The user checks the boxes for all “C1” scenarios because they are also out of date due to the “C1” demand being modified.

When you select OK to regenerate the scenarios, all options configured in the Scenario List Organizer are reapplied; see “Generating Scenarios” for details. Once scenarios are regenerated, all event labels and scenario names in the Simulator List Simulator and Scenario List Post-Processor dialog boxes return to black. Any added scenarios and scenarios that had results invalidated by the regeneration display a gray Run status icon, indicating the scenario needs to be resimulated. Unaffected scenarios continue to display the Run status they displayed before the scenarios were regenerated.

At this point, scenarios with a gray Run status icon can be resimulated and post-processed. Scenarios with a green Run icon do not need to be resimulated because their results were not affected by the changes to the input events.

After scenarios have simulated, you can execute a Windows batch script or any executable to notify you of the status. It is up to you to write the script, typically it will be a Windows Batch Script (.bat) file but can be any other executable (.exe).

To configure when and how simulation notifications are sent, select Workspace, then Options from the RiverSMART menu; alternatively, select the Options button on the RiverSMART toolbar.

In the Group area of the Options dialog box, select Script Execution.

Select one or more of the following check boxes to specify when to execute the notification batch scripts.

If diagnostics are enabled, as described in the“Workspace Menu” section, the Diagnostics Window displays messages generated by the batch scripts. It also displays information about the execution of the batch scripts themselves, including any errors.

If you select the Stop simulating scenarios if script execution fails check box, RiverSMART will stop simulating scenarios when there is an error in the execution of a script or the script/executable finishes unsuccessfully (with a non-zero status. This option prevents situations in which simulations are failing but no notifications are sent, and you are therefore not able to intervene.

The Scenario List Post-Processor dialog box displays a three-level tree view that lists the activated scenarios at the top level. Within each scenario, the events performed by post-processing are listed; and within each event, the completed activities are listed. To open this dialog box, select Scenarios, then Simulate Scenarios on the RiverSMART menu.

To initiate post-processing of scenarios, select one or more scenarios and one or more files, and then select Scenarios, then Post-Process Checked Scenarios. When a scenario is post-processed, its output files (that is, RDF or CSV) are run through the linked processes that follow each output file icon on the RiverSMART workspace. Post-processing typically involves taking an RDF file and running it through events, such as RDF Annualizer or RDF To Excel, to generate Excel workbooks that can be used for data analysis.

Files resulting from post-processing are managed by RiverSMART and are added to the Scenario\ folder of the study, in a folder with the scenario name. Log files or intermediate results are added to the Working\ folder of the study, in a folder with the event name.

If you need to halt post-processing while it is in progress, select Scenarios, then Stop Post-Processes. Post-processing of the current scenario is allowed to finish, and subsequent scenarios are not post-processed.

Figure 2.4 illustrates the following post-processing details for a scenario.

The Run icon displays the scenario simulation status: green for successful; red for unsuccessful; gray for not run.

The next column displays the Post-Processing Status icon. For a scenario, the post-processing statuses are: green for all run successfully; red for all failed; half-red and half-green for some steps successful and some failed; gray for not processed. You can manually override the Post-processing icon color by selecting Scenarios, then Mark Checked Scenarios As Post-Processed or Mark Checked Scenarios As Not Post-Processed. This is useful if the study was not saved after post-processing, causing the icons to indicate an outdated status.

If you select the File Folder icon at the end of a scenario row, a Windows Explorer window opens to the folder where the output files for the scenario are located.

When you expand a scenario tree view, additional post-processing details are displayed. The Post-processing icon displays the status of each post-processing event for the scenario.

When you select an event, its post-processing status is displayed in the status area of the window. If the event was unsuccessful, the reported error message is displayed in a second line of the status message.

If a post-processing event reports detail about its activities, the activities are listed at the next level in the tree view under the event. A green check indicates the activity was successful, and a red check indicates the activity failed.

When you select an activity, its post-processing status is displayed in the status area of the window. If a log file was generated for the activity, the File icon in the status message is enabled and you can select it to open the log file for viewing. This is useful in troubleshooting issues for failed activities.

Following is a sample log file generated by GPAT Graphs for the successful Stateline Flow Graphs activity highlighted in Figure 2.4.

The Scenario List Post-Processor window also provides options to deactivate or activate, and dynamically hide or show scenarios. These options function in the same manner as those on the Scenario List Organizer dialog box.

Deactivating a scenario makes it unavailable throughout RiverSMART and removes it from all RiverSMART dialog boxes. To deactivate scenarios, select the scenarios, and then select Edit, then Deactivate Checked Scenarios. To activate all inactive scenarios, select Edit, then Activate Inactive Scenarios.

Hiding a scenario does not deactivate it; it simply hides the scenario in the current dialog box and does not affect other dialog boxes. If many scenarios have been successfully post-processed, you may want to hide them to reduce clutter on the workspace. To hide active scenarios, select the scenarios, and then select View, then Hide Checked Scenarios. To show all active scenarios, select View, then Show Hidden Scenarios.

Scenario sets are user-defined groups of scenarios that help you to analyze and compare results across scenarios. When a study includes many scenarios, it may be impractical to include all of them on a single plot because the resulting graph would be too cluttered. Using scenario sets, you can group scenarios that you want to compare. For example, you can create a set for all scenarios that have the same hydrology but different demands and policies; or you can create a set for scenarios with a common policy but differing demands and hydrologies.

The Scenario Set Manager dialog box allows you to define scenarios sets. To open this dialog box, select Scenarios, then Scenario Set Management on the RiverSMART menu.

The Scenario Set Manager dialog box displays defined scenario sets. When you select a set in the Scenario Sets panel, the Scenarios panel displays the scenarios in that set. You can perform the following operations in the Scenario Sets panel.

The Scenarios panel has two modes, as follows. In both modes, the scenarios are listed in the order defined in the Scenario List Simulator dialog box; see “Display Order” for details.

This section describes processing of scenario sets, which differs from post-processing of individual scenarios. See “Post-processing Scenarios” for details about post-processing individual scenarios.

You can configure scenario sets as input for GPAT Graphs, the R Plugin events, and the CSV Combiner. You specify the scenario sets as inputs in the event configuration; then when a scenario set is processed, the input files linked to the event are retrieved for each scenario in the set, and all are passed together to the event for processing.

To start event processing using scenario sets, select the appropriate option on the RiverSMART Scenarios menu, as follows.

Log files generated by a GPAT Graphs event, R Plugin event, or CSV Combiner event are added to the Working\ folder of the Study Folder, in a folder named for the event.