How can I add a comment or documentation for a structure?

You can easily create attributes that can be apply to any kind of node. You can create a Documentation concept, which extends NodeAttribute. Documentation would hold your comment. To add it you would need to create an appropriate intention.

I hope it helps.

Hi Federico Tomassetti,

Thank you very much.

I will try this one. If I correctly understood, the attributed node is "concept_declaration" concept. Please correct me if I am wrong. I am just a newbie. 

Thanks and Regards, 

Dinesh.

I think that if you do like this you would be able to add comments only to concept declarations, while you want to apply comments to EVERY node. To do so I would use BaseConcept as the attributed node, because every concept extends BaseConcept.

Thank you very much. That really helped me a lot. :) 

Happy to hear that. Have fun using MPS!