In most cases, you should not need to write filters from scratch. You can create most of your filters using the administration console. You can then modify the filter.conf and filterrules.conf files to make any desired changes. These files reside in the directory /var/opt/SUNWportal/searchservers/search1/config.
However, if you want to create a more complex set of parameters, you will need to edit the configuration files used by the robot.
Follow these points when writing or modifying a filter:
The order of execution of directives (especially the available information at each phase)
The order of rules
For a discussion of the parameters you can modify in the robot.conf file, the robot application functions that you can use in the filter.conf file, and how to create your own robot application functions, see the Sun Java System Portal Server 7.1 Developer's Guide.