Issue 1312:  Keyword Identifiers(03) (obv-rtf)
Source:  (, )
Nature:  Uncategorized Issue
Severity: 
Summary: Summary: The Objects By Value (OBV) Specification (orbos/98-01-18) introduced
 the concept of "keyword identifiers" in an effort to avoid breaking
 existing IDL specifications. It specifies that a keyword identifier
 is a word that is treated as a keyword only when used in a keyword
 context, and is otherwise treated as a regular identifier.
 3) It allows IDL specifications that, while not unparseable, are
 highly ambiguous, especially to a human reader. For example, Jeff
 recently posted answers on how the following is to be parsed, but
 there is no way that someone reading the OBV spec would be able to
 figure out the rules he gave:
 
 interface public { ... };
 interface custom { ... };
 value safe { ... };
 
 value foo : safe { ... };        // Is this legal or an error?
 value foo2 : safe safe { ... };  // What about this?
 value foo3 {
     public x;         // Is this legal or an error?
     public public y;  // What about this?
     custom value();   // Is this a valid operation or a syntax error?
 };
 
 While all of these constructs can all be parsed using the appropriate
 number of look-ahead tokens (by the way, the grammar is *not* LALR(1)
 as the OBV Spec suggests), it is hard to read and even harder to
 parse correctly. Many IDL compilers still fail to properly implement
 the name lookup rules in the existing CORBA specification, and adding
 keyword identifiers will only make that situation much worse.
 
 

Resolution: 
Revised Text: 
Actions taken:
May 8, 1998: received issue
July 30, 1998: closed issue
Discussion: 

End of Annotations:=====
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Date: Thu, 07 May 1998 17:44:17 -0400
To: obv-rtf@omg.org, issues@omg.org
From: Steve Vinoski <vinoski@iona.com>
Subject: let's lose keyword identifiers

The Objects By Value (OBV) Specification (orbos/98-01-18) introduced
the concept of "keyword identifiers" in an effort to avoid breaking
existing IDL specifications. It specifies that a keyword identifier
is a word that is treated as a keyword only when used in a keyword
context, and is otherwise treated as a regular identifier.

As a solution, keyword identifiers create a significant long-term
penalty in order to correct a short-term problem. They raise more
issues than they solve:

3) It allows IDL specifications that, while not unparseable, are
highly ambiguous, especially to a human reader. For example, Jeff
recently posted answers on how the following is to be parsed, but
there is no way that someone reading the OBV spec would be able to
figure out the rules he gave:

interface public { ... };
interface custom { ... };
value safe { ... };

value foo : safe { ... };        // Is this legal or an error?
value foo2 : safe safe { ... };  // What about this?
value foo3 {
    public x;         // Is this legal or an error?
    public public y;  // What about this?
    custom value();   // Is this a valid operation or a syntax error?
};

While all of these constructs can all be parsed using the appropriate
number of look-ahead tokens (by the way, the grammar is *not* LALR(1)
as the OBV Spec suggests), it is hard to read and even harder to
parse correctly. Many IDL compilers still fail to properly implement
the name lookup rules in the existing CORBA specification, and adding
keyword identifiers will only make that situation much worse.