SDL SmartTarget 2011 SP3 Content Delivery Logback configuration example. From SmartTarget installation media.

SmartTarget logback example.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true">
    <!-- Properties -->
    <property name="log.pattern" value="%date %-5level %logger{0} - %message%n"/>
    <property name="log.history" value="7"/>
    <property name="log.folder" value="c:/tridion/log"/>
    <property name="log.level" value="WARN"/>

    <!-- Appenders -->
    <appender name="rollingSmartTargetLog" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${log.folder}/smarttarget.%d{yyyy-MM-dd}.log</fileNamePattern>
            <maxHistory>${log.history}</maxHistory>
        </rollingPolicy>
        <encoder>
            <pattern>${log.pattern}</pattern>
        </encoder>
        <prudent>true</prudent>
    </appender>
	
    <!-- Loggers -->
    <!-- All Java based smarttarget -->
    <logger name="com.tridion.smarttarget" level="${log.level}">
        <appender-ref ref="rollingSmartTargetLog"/>
    </logger>
    <!-- specific one for ambientdata -->
    <logger name="com.tridion.smarttarget.ambientdata" level="${log.level}">
        <appender-ref ref="rollingSmartTargetLog"/>
    </logger>
    <!-- all .Net logs through Juggernet -->
    <logger name="Tridion.SmartTarget" level="${log.level}">
        <appender-ref ref="rollingSmartTargetLog"/>
    </logger>
</configuration>