A customer wanted me to post my example to this forum:

From: ramnararyan [mailto:ramnarayan@xxxxxxxx]

Hi,
   I got information from cdnuser forum that u have example code of the dpi import/export declarations, and the export function inside the interface, and you were able to access the import function from both modules attached to the interface. so i would like to adopt this methodology.I m using NCSIM 6.2.

please send me example.
-----------------
so here is the example.  This example has more than the orginal request, it also shows how to pass a queue of class thru an interface, as well as how to access DPI inside an interface:

-----file: class_across_interface.sv---------------
// Todd Mackett Cadence Design Systems
//  irun class_across_interface.sv dpi.c
// tested with IUS5.83s1 and IUS6.2s1
/*  
 top--------------------------
 | test --->interface---->dut |
 |-----------------------------
*/

package mypack;
 class some_class;
  int some_int;
  real some_real;
  protected string some_string;  // needs to be protected for IUS5.83

 function void set_data (int i, real r, string s);
  some_int =i;
  some_real = r;
  some_string = s;
 endfunction

 task get_data(output int i, output real r, output string s);
   i = some_int;
   r = some_real;
   s = some_string;
 endtask

 function void print_data();
  $display("Int: %d, Real: %f, String: %s", some_int, some_real, some_string);
 endfunction

  endclass
endpackage
// ------

// This channel is an interface that is a queue of classes
interface myIF;
import mypack::*;

// -----dpi------
import "DPI-C" context c_func = function int my_c_func (input int a);
export "DPI-C" sv_func = function my_sv_func;

function int my_sv_func(input int a); 
  return a + 2;
endfunction
// -----end dpi-----
event some_event;

some_class some_classQ[$]

function int some_classQ_size();
  return some_classQ.size();
endfunction

task push_class_in_Q(input some_class Qin);
  some_classQ.push_front(Qin);
endtask

task pop_class_out_Q(output some_class Qout);
  Qout = some_classQ.pop_back();
endtask

endinterface

// -----------------
module top();

int top_int;
reg clk = 'b1;

initial
 forever clk = #10 ~clk;  // system clk

myIF myIFi();  // instantiate interface

test testi(clk, myIFi);

dut duti(clk, myIFi);

endmodule
// --------------
// The test module create a class of information and puts it in the 
// channel (a queue in the interface)

module test (input clk, myIF myIFi);
import mypack::*;
int i;
real r;
string s;

initial
  #200 $finish;

some_class top_class;

always @(posedge clk)
begin
 top_class = new;
  i = $urandom_range(5,1);

  randcase
   1: r = 3.14;
   1: r = 123.456;
   1: r = -943.825;
  endcase

  randcase
   1:  s = "IUS SystemVerilog";
   1:  s = "Cadence";
   1:  s = "Who needs VHDL?";
  endcase

// dpi call inside interface:
 $display("DPI Call %d", myIFi.my_c_func(30));

  top_class.set_data(i, r, s);  // set the values into class

  myIFi.push_class_in_Q(top_class);  // transmit the class

  -> myIFi.some_event;  // cause the event
end
endmodule

// The dut module consumes the class when the event is valid
// and displays its contents as it comes across the interface

module dut (input clk, myIF myIFi);
import mypack::*;

some_class dut_class =new;

always @(myIFi.some_event) // process event
begin
  $display("\nQueue Size %d",myIFi.some_classQ_size() );
  myIFi.pop_class_out_Q(dut_class);
  dut_class.print_data();
// dpi call inside interface:
 $display("DPI Call %d", myIFi.my_c_func(997));
end

endmodule
-------------end file: class_across_interface.sv---------------

----file: dpi.c--------
#include "dpi.h" 

//extern int sv_func(int a);

int c_func(int a) {

  return sv_func(a); 
}
-----end file: dpi.c---------

----partial irun.log file:--------
Queue Size           1
Int:           1, Real: 3.140000, String: Who needs VHDL?
DPI Call         999
DPI Call          32
... ... ...