In Job Description Parsing, we categorize the skills either as a Required skill or as a Preferred skill on the basis of our context vocabulary. Based on the vocabulary, the parser decides whether a skill is required or preferred skill.
For example, Skill with a keyword like an Experience, Essential, Strong Knowledge, etc. are considered as context for Required skills.
And the Skill with Keywords like Preferred, Desire, Knowledge, good, Proficiency With, is a plus, Desired, etc. are considered as context for preferred skills.