[wg11] EXPRESS (DERIVEd) attribute redeclaration question

[Lothar Klein]

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.

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