[wg11] EXPRESS (DERIVEd) attribute redeclaration question

[thomas thurman]

Thanks Jochen!

Best Regards,
Tom
>On Jun 5, 2012, at 5:26 AM, Jochen Haenisch wrote:

> Tom,
> 
> my conclusion is that the error message is correct. According to P11
> 9.2.7 Specialization, only the data type counts when determining whether
> a redeclared attribute follows the specialization rule or not.
> Assignments have in this context nothing to say.
> 
> Best regards,
> Jochen
> -----Original Message-----
> From: wg11-bounces at steptools.com [mailto:wg11-bounces at steptools.com] On
> Behalf Of Thomas Thurman
> Sent: 1. juni 2012 23:34
> To: Lothar Klein
> Cc: wg11
> Subject: Re: [wg11] EXPRESS (DERIVEd) attribute redeclaration question
> 
> 
> On Jun 1, 2012, at 3:27 PM6/1/12, Lothar Klein wrote:
> 
>> It has been always this way.
>> And the classical example is that if an entity A has an explicit
>> INTEGER attribute and two subtypes B and C. In B the attribute is
>> redeclared to be an odd number and in C to be an even number and there
>> is an entity D that is a subtype of both, B and C then all this is
>> valid Express. But it is not possible to construct a valid instance of
>> D because you won't find an integer value that is both an odd and an
> even
>> number simultaneously.
> Sorry, we seem to be getting off track.
> I was specifically talking about the case where there are three
> declarations in a direct supertype path,
> The root supertype, an intermediate type and the leaf subtype.
> Let's not mix up the problem statement.
> 
> Tom
>> 
>> Lothar
>> 
>> Friday, June 1, 2012, 3:42:25 PM, you wrote:
>>> Phil,
>>> This is an interesting conclusion. I look forward to hear opinions of
> other members of WG11.
>> 
>>> Tom
>>>> On Jun 1, 2012, at 12:43 AM6/1/12, Phil Spiby wrote:
>> 
>>>> I believe Rule and Restriction (e) under section 9.2.3.4 applies:
>>>> e) If an attribute of a supertype is redeclared in two non-mutually
> exclusive subtypes, an
>>>> instance which contains both subtypes shall have a single value for
> that attribute which is
>>>> valid for both redeclarations.
>>>> 
>>>> Phil
>> 
> 
> 
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