As far as I know, Constitutional assembly has been there in many countries including Norway, Sweden, South Africa, Timor to name a few.In Norway, CA was first done in 1814. As far as I have understood, it is a body which drafts a new constitution which is then left to the people to accept or reject by voting. It is a long process which takes at least 1 to 2 or more years. 1) First a Constututional Assembly if formed of some members of the parliament, distinguished judges and lawyers, some cabinet members and members from the head of the state. The appointment is done by the parliament. 2) A time, usually up to 6 mth is spent by this assembly in which the current constitution is studied in detail and the clause which need change or rectification are listed. Then discussions are held on these points and drafts of the changes to be made is prepared. Two third majority of this assembly must approve the draft.This may take another 6 mth. 3) The final draft is sent to head of state for approval. 4) Those points in the draft which are in a debate and about which no consensus can be reached in the CA, are put forward in front of the people and voting for this is held like general elections. The people can either accept or reject these points. 5) The final constitution is then made. Maoists wanted CA from the street and not from the Sansad, probably becoz they didn't want members from head of state side etc in this assembly. But CA through sansad is the democratic process and everyone should accept it.