A person would be playing different roles in the strategic initiative which would be :

Authority  Role ( Generally, with the Head of Organisation but he shares this through creating policies defining the authority he delegates with each role)
Responsible Role ( The person is supposed to accomplish the work using his ability for same)
Collaboration Role ( The person should be able to do the work with efficiency and quality)
Informing Role ( The person who shall rate the accountability reward to punish or in other world who checks that the procedures and policies were followed )

Responsibility and accountability work hand in hand to understand simply that Responsibility is a self monitored think while accountability is others evaluation.  This works the following way-

I am responsible to drive safely while I am accountable to follow the Traffic rules ( I may still be driving safely by jumping red lights but I shall be breaking rules that I was accountable for), So any person having responsibility is automatically accountable. There can be a scenario where he is finally accountable to himself, if he is the CEO.

The Larger the Accountability the More is the Reward. The Job description actually defines to whom the position reports, specifications such as the Competencies or skills needed by the person in the job. This also defines his Pay structure and allowances. 

Based on all this, the final stage for execution plan comes, wherein some person is finally given this work with different roles to play for different work. Based on  his competencies, required for this work and then creating this general identity in an organisation, a Designation is created.  This is required so that the company is not person dependent as that is a replaceable identity but the job is a permanent identity therefore in organizations this job purpose is assigned to designations and people are linked to those designations.