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In HPS Java terminology, a Driver processes events and can read or add collection data.  A Driver can create histograms from physics data or implement a step of physics reconstruction.  Drivers are executed in order, and a Driver can have child Drivers to implement complex behavior.  A chain of Drivers is activated by the "mother of all drivers" which contains a list of the top level Drivers as children.

Driver

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Example

package org.hps.users.jeremym;

import org.lcsim.event.EventHeader;
import org.lcsim.geometry.Detector;
import org.lcsim.util.Driver;

public class ExampleDriver extends Driver {

    private int value;
  
    public void process(EventHeader event) {        
    }

    protected void detectorChanged(Detector detector) {
    }
    
    protected void endOfData() {
    }

    protected void startOfData() {        
    }
 
    public void setValue(int value) {
        this.value = value;
    }
}

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The lcsim xml format can describe drivers and their parameters at runtime using an XML data description.  The Guidelines for Creating Compatible Drivers describes how to write a Driver so that it can be using in the XML steering files.

Here is sample XML which calls the ExampleDriver and sets a parameter value on it.

<lcsim xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:noNamespaceSchemaLocation="http://www.lcsim.org/schemas/lcsim/1.0/lcsim.xsd">       
    <execute>
        <driver name="ExampleDriver"/>
    </execute>    
    <drivers>
        <driver name="ExampleDriver" type="org.hps.users.jeremym.ExampleDriver">
            <value>1234</value>
        </driver>
    </drivers>
</lcsim>

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