Here is an example of how the IncludeAction class from the logback.core package could be used in a configuration file for Logback, a logging framework for Java:

<configuration>
  <include resource="subconfig.xml" />

  <appender name="FILE" class="ch.qos.logback.core.FileAppender">
    <file>mylog.log</file>
    <encoder>
      <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
    </encoder>
  </appender>

  <root level="debug">
    <appender-ref ref="FILE" />
  </root>
</configuration>

In this example, the element tells Logback to include the contents of the file subconfig.xml at this point in the configuration. This allows you to split your configuration across multiple files for easier organization and management. The and elements are used to configure the appenders and log levels for the logger. In this example, a FileAppender is being used to write log messages to a file called "mylog.log" with specific pattern.

Note that you need to include the logback core library in your classpath.