Semantic annotation using Schema.org vocabulary

[muety]

Introduce semantics to KitSquid by adding Schema.org annotation in RDFa format.

• https://schema.org/CollegeOrUniversity
• https://schema.org/Person
• https://schema.org/Course
• https://schema.org/CourseInstance
• https://schema.org/UserComments
• https://schema.org/AggregateRating
• https://schema.org/DateTime