Is it possible to add an attribute to the entity dynamically in runtime ?

Hi Team !                 One employee has one trainee. He can able to rate his trainee based on his inter personal skills like technical skill, communication skill and etc. So I have one rating entity in my domain model which have some attributes like Skills (String), Status (Enumuration). But my requirement is I want to add skills dynamically. Whenever employee want to add any other skills to trainee profile, it should be possible. Is this possible to add an attribute dynamically ? Or If you have any idea about my query, Please kindly share your ideas in comment section. Thanks for the reply in advance ! 
1 answers

Attributes are fixed in the model.

If you need to add skills, you need to put them in a separate skills-entity and create an association between trainees and skills.