Issue 1778:  Need to specify when are side-effects allowed (mof-rtf)
Source:  (, )
Nature:  Revision
Severity:  Minor
Summary: Summary: The MOF was designed under the assumption that ordinary 
 (i.e. non-derived) M1-level attribute values and links only change 
 when the client expects them to.  Unfortunately, the spec
 does not address this issue.  In particular, it does not say
 what mapped IDL operations are allowed to change things by
 side-effect.
 
 

Resolution: resolved and closed
Revised Text: 
Actions taken:
August 6, 1998: received issue
May 8, 2000: closed issue
Discussion: 
1. Add text to define "visible state" (object identity, non-derived attribute values and
links) and "hidden state" (other state).
2. Add text to specify which mapped operations can alter which kinds of state. For ex-ample,
setting a non-derived attribute cannot have side-effects on any other visible
state.
Implementation: Added above as subsections of Section 4.11, “A Style Guide for
Metadata Computational Semantics,” on page 4-21. Done. [SC]
End of Annotations:=====
Return-Path: <crawley@dstc.edu.au>
To: mof-rtf@omg.org, issues@omg.org
Subject: Need to specify when are side-effects allowed
Date: Thu, 06 Aug 1998 14:51:23 +1000
From: Stephen Crawley <crawley@dstc.edu.au>


Source: DSTC (Dr. Stephen Crawley, crawley@dstc.edu.au)
Nature: Revision
Severity: Minor
Summary:  The MOF was designed under the assumption that ordinary 
(i.e. non-derived) M1-level attribute values and links only change 
when the client expects them to.  Unfortunately, the spec
does not address this issue.  In particular, it does not say
what mapped IDL operations are allowed to change things by
side-effect.

Additional Text:

For the purpose of this discussion:

   The "explicit state" of a model is that which is defined by
   the Classes, their (non-derived) MofAttributes and the
(non-derived)
   Associations between them.   Any other state is called "hidden 
   state".

   A "side-effect" is a change to the explicit state of a model that 
   results from something other than a mapped operation for the
   model element that defines the state.

I tentatively propose that only IDL operations corresponding to
the following be allowed to have side-effects on explicit state
(as defined above):

   Operations with is_query == false

   MofAttributes with is_derived == true && is_changeable == true,
       and where the operation is an update

   Associations / AssociationEnds / References where the 
       Association has is_derived == true and the Reference or 
       AssociationEnd has is_changeable == true,
       and where the operation is an update 

[I don't propose that we limit changes to hidden state.  For example,
the hidden variable for a derived Attribute that holds a count of the 
number of reads on some other Attribute.  We may want to tighten this 
up later, when the MOF Model supports behavioral specification of 
Operations and derived MofAttributes and Associations.  However, that 
is beyond the scope of this RTF.]