[wg11] EXPRESS Section 11 question

[Ed Barkmeyer]

Alan R Williams wrote:

> I think it needs something like:
> 
> "An entity which is either explicitly REFERENCE'd or implicitly
> interfaced shall only be dependently instantiated.  A dependently instantiated 
> entity instance must play the role described by either an
> attribute of an instantiation of an entity in  
> the interfacing schema or an attribute of another dependently instantiated 
> entity instance."
> 
> The definition is recursive and so should work back up an attribute chain.

Agree.  This is better.  There is still a small problem.  I suggest:

"An entity which is either explicitly REFERENCE'd or implicitly
interfaced shall only be dependently instantiated.
A dependently instantiated entity instance shall play the role described 
by an attribute of either:
- an instance of an entity data type that was either declared locally 
within or USE’d by the schema, or
- another dependently instantiated entity instance."

I would also be tempted to insert a Note:
Note:  With the above definitions, "dependently instantiated" is *not* 
the complement of "independently instantiated".  There are (potential) 
instantiations [of the kind Alan exemplified] that are neither.  But 
those instantiations are not valid!

Now I suppose we need to construct the formal SEDS, i.e. "deficiency 
report" in ISO terms.

Thanks,
-Ed

P.S. The intended interpretation of "play the role described by an 
attribute" whose data type is SET [1:?] OF <entity> belies the idea that 
the role is played by the *value* of the attribute.  The SET does not in 
fact play the role; the individual entity instances in it do.  If it 
were the SET that played the role, the dependent instantiation rule 
would not be satisfied.  But that is clearly NOT what was intended. 
What "plays the role described by an attribute" is therefore not 
necessarily the "value of the attribute".

-- 
Edward J. Barkmeyer                        Email: edbark at nist.gov
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8264                Tel: +1 301-975-3528
Gaithersburg, MD 20899-8264                FAX: +1 301-975-4694

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