Naive Qs about selinux modules

Q:  Can any SELinux directive be put into a policy smodule, or are there restrictions?

For example: suppose I wanted to:

  allow snmpd_t apmd_t:process ptrace;

  allow snmpd_t auditd_t:process ptrace;

  allow snmpd_t automount_t:process ptrace;

 [ …and so on ]

so that snmpd could access mib .1.3.6.1.2.1.6. (advisability notwithstanding) Could these directives be put into a policy module even though the base policy already has an snmpd i/f?

Q.  Can a module define new booleans?  If so are they persistent if the module is unloaded and reloaded?

For example; an snmpd policy module with an snmpd_can_ptrace boolean.  Are there namespace conventions?

Q. What happens if the base policy (or another policy modules) is updated with overlapping statements.

Am I correct in believing that the set of allows is the union of the base allows + all module allows?

--rich