Competency Mapping for Summer Project: How Do I Write Job Descriptions and Perform Gap Analysis?

My summer project is on competency mapping. Under this project, I have to write job descriptions for any three job roles, then compare them with the available job descriptions and perform Gap Analysis to make recommendations. Please help me out. What procedures and steps should I follow?

Please search CiteHR where Competency Mapping has already been covered.

Also, please see my posts on Research Methodology.

Thank you for the relevant information. In my project, I need to map the key competencies of sales and finance managers. I work for an FMCG company. Could you please provide some details about the key competencies required by sales and finance managers from novice to expert levels? Your help would be greatly appreciated.