Four friends engaged in conversation.
friends chatting
Chatting isn't the same thing as a conversation. Conversations are a little deeper than just chatting.
exists e1 x1 x2.(in(e1,x2) & n_conversation(x2) & Theme(e1,x1) & v_engage(e1) & n_friend(x1) & card_eq_4(x1))
exists e1 x1 x2.(a_topic(x1) & Actor(e1,x2) & v_chat(e1) & (x1 = x2) & n_friend(x1))