Something

        public static void GenXmlSchemas()
        {
            NpgsqlConnection Connection = new NpgsqlConnection(GenConnectionString());
            NpgsqlDataAdapter gAdapter = new Npgsql.NpgsqlDataAdapter(
                "SELECT * FROM \"groups\"",
                Connection);
            NpgsqlDataAdapter uAdapter = new Npgsql.NpgsqlDataAdapter(
                "SELECT * FROM \"users\"",
                Connection);
            NpgsqlDataAdapter tAdapter = new Npgsql.NpgsqlDataAdapter(
                "SELECT * FROM \"terms\"",
                Connection);
            //Npgsql.NpgsqlCommandBuilder b = new Npgsql.NpgsqlCommandBuilder(adapter);
            DataSet ds = new DataSet();
            gAdapter.Fill(ds);
            uAdapter.Fill(ds);
            tAdapter.Fill(ds);
            ds.WriteXmlSchema("/tmp/tukia.xsd");
        }