This document describes the steps to create a new user defined operator with ODL.

Name

First you need to choose a meaningful name for the new operator. Note, there is no other operator with the same name.

operator ODLSelect {
	//...
}

Metadata

Next you can set metadata to configure the operator with static information.

operator ODLSelect(outputMode = "INPUT", minInputPorts = 1, maxInputPorts = 1){
    //...
}

The following table shows the available metadata:

Please look at the LogicalOperator-Interface of Odysseus for more available metadata (e.g. doc, url, category).

Parameter

You need to define parameters if the operator should be configurable while building a continuous query. A parameter can be optional and consists of a data type and a name.

operator ODLSelect(outputMode = "INPUT", minInputPorts = 1, maxInputPorts = 1){   

    parameter IPredicate predicate;

    optional parameter int heartbeatrate;

}

Note that not every data type can be used for a parameter because each data type must have a corresponding parameter class in Odysseus. The following table shows the available data types:

Some data types have more than one corresponding parameter class. In these cases you can optionally set a parameter class as a metadata of a parameter. Please look at the Parameter-Interface of Odysseus for more available metadata.

operator ODLProject(outputMode ="MODIFIED_INPUT", minInputPorts = 1, maxInputPorts = 1){    
    
    parameter(type=ResolvedSDFAttributeParameter) SDFAttribute[] attributes;
          
}