Javadocs- Interfaces (iProgram , iProject)

 I'm trying to add attachments to a Task using process extensions, but was wondering which Interface would best suit to create the documents in the Attachment table(IProgram or IProject). how to even access the Attachments table of the Task. Is there any Interface defined that is not listed in the Javadocs, something like iTask or IPhase? Please advice.

Thanks,

Usha