Creating a Process
SensorML processes require a process implementation in Java as well as a process description in SensorML to define data sources, output structures, and parameters.
Java Implementation
Required Files
The OSH module containing the processing implementation should include at least 3 files. These files are:
-
Activator - OSGi bundle activator, this is the same as any OSH module
-
ProcessDescriptor - Descriptor to add your process implementation to OSH’s process manager
-
(Process Implementation) - Process implementation as an extension of ExecutableProcessImpl
Typical OSH Module Files
-
org.sensorhub.api.processing.IProcessProvider - Provider to allow OSH to find the executable process
-
build.gradle
public class Activator extends OshBundleActivator implements BundleActivator
{}
public class ProcessDescriptors extends AbstractProcessProvider {
public ProcessDescriptors() {
// Adds the process implementation to the process manager using the ProcessInfo defined in the implementation
addImpl(MyProcess.INFO);
}
}
Replace the below with the path to your Descriptor
classpath.to.ProcessDescriptors
public class MyProcess extends ExecutableProcessImpl {
// Required process information
public static final OSHProcessInfo INFO = new OSHProcessInfo("myprocessname", "An example process", null, MyProcess.class);
Count input1;
Count output1;
Count parameter1;
public MyProcess() {
super(INFO);
SWEHelper fac = new SWEHelper();
// Initialize inputs, outputs, params
inputData.add("input1", input1 = fac.createCount().build());
outputData.add("output1", output1 = fac.createCount().build());
paramData.add("param1", parameter1 = fac.createCount().build());
}
@Override
public void execute() throws ProcessException {
// Use inputs and params to update outputs
int paramValue = parameter1.getData().getIntValue();
int inputValue = input1.getData().getIntValue();
int equation = inputValue * paramValue;
output1.getData().setIntValue(equation);
}
}
Executing the Process
Ensure that your process module is included in the project’s build.gradle.
In order to execute the created process, a SensorML process description must be provided to pass to the SensorML Stream Process Module in OSH.
SensorML Process Chain Description
A SensorML process chain description is an Aggregate Process composed of inputs, outputs, parameters, components, and connections.
This required SensorML process chain description has a few requirements as listed below.
Requirements
-
ID - Unique identifier of the process chain
-
Outputs - These will be the top-level outputs available from the datastream created by the aggregate process.
-
Components - These are chained together to create your final process. Components can be any of the following
-
Datastream - Datasource stream to read outputs and connect to other parts of the aggregate process.
-
Command stream - Can be used as a destination for process or datastream outputs. Commands will be sent at the rate that the linked output is updated.
-
Processes - Process inputs, outputs, and parameters can be chained together once defined as a component.
-
-
Connections - These are explicitly defined connections to link inputs to outputs or vice-versa. Connections can only be between 2 data records that have the same record structure.
This description will use the previous Java implementation as the sample process.
<sml:AggregateProcess xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:sml="http://www.opengis.net/sensorml/2.0" xmlns:swe="http://www.opengis.net/swe/2.0" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:gco="http://www.isotc211.org/2005/gco" xmlns:gmd="http://www.isotc211.org/2005/gmd" gml:id="F1">
<gml:identifier codeSpace="uid">UUID OR URN</gml:identifier>
<sml:outputs>
<sml:OutputList>
<sml:output name="output1">
<swe:Count>
<swe:label>Output 1</swe:label>
</swe:Count>
</sml:output>
</sml:OutputList>
</sml:outputs>
<sml:components>
<sml:ComponentList>
<sml:component name="source0">
<sml:SimpleProcess gml:id="F2">
<sml:typeOf xlink:href="urn:osh:process:datasource:stream"/>
<sml:configuration>
<sml:Settings>
<sml:setValue ref="parameters/producerURI">urn:of:system:with:datastream</sml:setValue>
</sml:Settings>
</sml:configuration>
</sml:SimpleProcess>
</sml:component>
<sml:component name="process0">
<sml:SimpleProcess gml:id="F3">
<sml:typeOf xlink:href="urn:osh:process:myprocessname"/>
<sml:inputs>
<sml:InputList>
<sml:input name="input1">
<swe:Count>
<swe:label>Input 1</swe:label>
</swe:Count>
</sml:input>
</sml:InputList>
</sml:inputs>
<sml:outputs>
<sml:OutputList>
<sml:output name="output1">
<swe:Count>
<swe:label>Output 1</swe:label>
</swe:Count>
</sml:output>
</sml:OutputList>
</sml:outputs>
<sml:parameters>
<sml:ParameterList>
<sml:parameter name="param1">
<swe:Count>
<swe:label>Parameter 1</swe:label>
<swe:value>12345</swe:value>
</swe:Count>
</sml:parameter>
</sml:ParameterList>
</sml:parameters>
</sml:SimpleProcess>
</sml:component>
<sml:component name="control0">
<sml:SimpleProcess gml:id="F4">
<sml:typeOf xlink:href="urn:osh:process:datasink:commandstream"/>
<sml:configuration>
<sml:Settings>
<sml:setValue ref="parameters/systemUID">urn:to:system:with:controlstreams</sml:setValue>
<sml:setValue ref="parameters/inputName">controlStream1</sml:setValue>
</sml:Settings>
</sml:configuration>
</sml:SimpleProcess>
</sml:component>
</sml:ComponentList>
</sml:components>
<sml:connections>
<sml:ConnectionList>
<sml:connection>
<sml:Link>
<sml:source ref="components/source0/outputs/GenericOutput/anyOutputMatchingInput1Struct"/>
<sml:destination ref="components/process0/inputs/input1"/>
</sml:Link>
</sml:connection>
<sml:connection>
<sml:Link>
<sml:source ref="components/process0/outputs/output1"/>
<sml:destination ref="components/control0/inputs/controlStream1/anyInputMatchingOutput1Struct"/>
</sml:Link>
</sml:connection>
<sml:connection>
<sml:Link>
<sml:source ref="components/process0/outputs/output1"/>
<sml:destination ref="outputs/output1"/>
</sml:Link>
</sml:connection>
</sml:ConnectionList>
</sml:connections>
</sml:AggregateProcess>
Process Description Helpers
TODO