mysql - Representation of a simple messeger application using a database -

in application there users, conversations , messages. more 2 users participate in conversation.

i thinking this:(---- relations, capital_words entities)

message ---- conversation ---- user

msg contains sender , content sent;
conversation contains users participate in conversation;

but not enough because sender user , there link between msg , user. if add relation have problem because sender should user participate conversation.(there is-a relation if i'm not mistaking)

i don't know how model problem. if conversation between 2 users, need message , user. in fact conversation entity pretty strange.

if eliminate conversation initial problem have add in message field contains list of partecipants. in way miss concept of conversation , if have retrieve msgs related conversation need join of data :) . --> impractical

i appreciate every suggestion. don't know if database idea kind of application. thought not difficult work with.(keeping in mind can lose performance)