a crazy problem

[Rock Lee]

Hello
I'm a begginer in VHDL
I want to describe 74193 with the VHDL but I fail
the code is:
library ieee;
use ieee.std_logic_1164.all;
USE ieee.Std_logic_unsigned.all;

entity counter is
port (
aftellen : in std_logic; -- kloksignaal aftellen
optellen : in std_logic; -- kloksignaal optellen
clear : in std_logic; -- clear
enable : in std_logic; -- enable signaal
load : in std_logic; -- load
data_in : in std_logic_vector(3 downto 0); -- data ingangen
data_out : out std_logic_vector(3 downto 0); -- telleruitgangen
carry_out : out std_logic -- carry out
);
end counter ;

architecture gedrag of counter is
signal uit : std_logic_vector(3 downto 0); --signaal variable (buffer)
begin
process(optellen,aftellen,clear,load)
begin
if (optellen'event and optellen = '1')then --event driven (als de flank omlaag gaat)
if(clear = '0')then
if (uit = "1111") then --als op max. komt dan
uit <= (others =>'0'); --teller op min. zetten
else
uit <= uit + 1; -- optellen --anders optellen
end if;
end if;
elsif (aftellen'event and aftellen = '1') then --event driven
if(clear = '0')then
if (uit = "0000") then --als teller op min. komt
uit <= "1111"; --teller op max. zetten
else
uit <= uit - 1; -- aftellen --anders aftellen
end if;
end if;
elsif (clear = '1') then --als clear hoog is
uit <= (others =>'0'); --clear buffer
elsif (load'event and load = '1') then --event driven (werkt niet in simulatie) als load laag wordt
if(clear = '0')then
data_out <= data_in after 2 ns; --data_out wordt data_in
end if;
end if;
data_out <= uit; --zet buffer in data_out
end process;
end gedrag;
6 errors at the same line(red)said: can't infer register for signal"uint[3]"because signal dose not hold its value outside clock edge
Can anyone help me?
Thanks!