The release order list is specified using the releaseorder modifier in the implementation section of the IDL file, as shown in the following sample code. In this example, the release order list groups related methods and data accordingly, that is, by instance variable and the functions that operate on that instance variable.

#ifndef  example_idl
#define  example_idl
#include <somobj.idl>

interface Example : SOMObject

{
  attribute string         szVar1;
  attribute unsigned long  ulVar2;

  void Show_All_Vars();

  #ifdef __SOMIDL__
  implementation
  {
    releaseorder:  Show_All_Vars,
                   _get_szVar1,
                   _set_szVar1,
                   _get_ulVar2,
                   _set_ulVar2;

    //# Class modifiers
    callstyle    = oidl;    // For compatibility with SOM1
    majorversion = 1;
    minorversion = 2;
  };
 #endif /* __SOMIDL__ */
};
#endif  /* Example_idl */

If a third attribute variable is added to the class definition file, compatibility with clients of the Example class defined in the previous sample code can be maintained by modifying the release order, as shown in the following sample code:

#ifndef  example_idl
#define  example_idl
#include <somobj.idl>

interface Example : SOMObject

{
  attribute string         szVar1;
  attribute char           chVar3;   /* New data added */
  attribute unsigned long  ulVar2;

  void Show_All_Vars();

  #ifdef __SOMIDL__
  implementation
  {
   /* Add new methods at the end of the release order */
   /* list to maintain compatibility with clients     */
    releaseorder:  Show_All_Vars,
                   _get_szVar1,
                   _set_szVar1,
                   _get_ulVar2,
                   _set_ulVar2,
                   _get_chVar3,
                   _set_chVar3;

    //# Class modifiers

    callstyle = oidl;    // For compatibility with SOM1
    majorversion = 1;
    minorversion = 2;
  };
#endif /* __SOMIDL__ */
};
#endif  /* example_idl */

In the previous figure, the new attribute chVar3 is added between the two existing attributes. The new method names, _get_chVar3 and _set_chVar3, are added to the end of the release order list.

Without a release order list, the data and methods in the first version of the Example class are processed in the order in which they occur in the file, as shown in in the following figure:

_get_szVar1, _set_szVar1, _get_ulVar2, _set_ulVar2, Show_All_Vars

Without a release order list, the methods in the second version of the Example class are processed in the order in which they occur in the file, as shown in in the following figure:

_get_szVar1, _set_szVar1, _get_chVar3, _set_Var3, _get_ulVar2, _set_ulVar2, Show_All_Vars

The method information maintained by SOM in the object data structures built for the first version of the Example class does not match that built for the second version of the Example class. The second version is not compatible with clients of the first version. Specifying a release order list, and adding new data and methods at the end of the list, ensures client compatibility.