I'm having troubles understanding the relation between additivity, category logging level and appender threshold...

here's the scenario (my log4j.properties file):

log4j.category.GeneralPurpose.classTypes=INFO, webAppLogger
log4j.additivity.GeneralPurpose.classTypes=true

log4j.category.GeneralPurpose=ERROR, defaultLogger
log4j.additivity.GeneralPurpose=false

log4j.appender.webAppLogger=org.apache.log4j.RollingFileAppender
log4j.appender.webAppLogger.File=webapps/someWebApp/logs/webApp.log
log4j.appender.webAppLogger.MaxFileSize=3000KB
log4j.appender.webAppLogger.MaxBackupIndex=10
log4j.appender.webAppLogger.layout=org.apache.log4j.PatternLayout
log4j.appender.webAppLogger.layout.ConversionPattern=%d [%t] (%F:%L) %-5p - %m%n
log4j.appender.webAppLogger.Encoding=UTF-8

log4j.appender.defaultLogger=org.apache.log4j.RollingFileAppender
log4j.appender.defaultLogger.File=logs/server.log
log4j.appender.defaultLogger.MaxFileSize=3000KB
log4j.appender.defaultLogger.MaxBackupIndex=10
log4j.appender.defaultLogger.layout=org.apache.log4j.PatternLayout
log4j.appender.defaultLogger.layout.ConversionPattern=%d [%t] (%F:%L) %-5p - %m%n
log4j.appender.defaultLogger.Encoding=UTF-8

insights: category GeneralPurpose.classTypes is INFO category GeneralPurpose.classTypes has additivity TRUE category GeneralPurpose is ERROR category GeneralPurpose has additivity FALSE

with the current configuration I would have assumed that INFO messages sent to category GeneralPurpose.classTypes.* would be only logged to webAppLogger since the parent logger (cateogry) is set with ERROR level logging. However, this is not the case, the message is logged twice (one in each log file). Looks like the ERROR logging level for the parent category is not taken into consideration when the event is sent as part of additivity...

1. is my observation correct or am I missing something ?
2. how should I alter the configuration in order to achieve only ERROR level loggings in server.log ?

thanks,

GBa.