BPEL is a web service orchestration language. It does not have constructs for querying databases or writing files to the file system. These functions would need to be performed in other web service implementation languages (such as Java) that could then be invoked from a BPEL process as a web service.
For future reference, usage questions should be asked on the 'riftsaw user' forum - this forum is intended for developers contributing to the riftsaw project.
Also, riftsaw is related to the integration of Apache ODE into the JBoss AS environment - so focuses on runtime. Questions related to the BPEL designer should be placed on the JBoss Tools user forum.