Properly assigning actors in an approval Workflow

I'd like help trying to produce a well thought out logical workflow (If this is the wrong forum please kindly let me know although I do think this is probably best answered by the slightly more scientifically minded audience here than by the guys over at User Experience).

I am trying to outline a workflow that involves various actors. Currently I have the Owner (or administrator), Approver(s) and contributor(s).

First some background. The purpose of the workflow is to satisfy a compliance need and to show content submitted is approved.

My premise is that there is a requirement to provide content which must be met by the contributor and then approved by the Approver.

I am trying to keep things simple so only one contributor may be assigned to a requirement.

However my question is who is more logical suited to producing a requirement ? Should it be the administrator (who invites the Approver?) or should it be the Approver themselves since they are more likely to know what they are seeking and less likely to reject a requirement if they themselves wrote it ?

In other words would me allowing an Approver to provide a requirement lend credibility to the process or detract from it ? If the former would it then be reasonable for an Approver to nominate the contributor and assign them the requirement?

Should I consider adding additional actors such as a Requirement Proposer ?