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Re: union of a union legal?

From: Takuki Kamiya <takuki@pacbell.net>
Date: Fri, 1 Feb 2002 18:18:53 -0800
Message-ID: <01ed01c1ab8f$f671f120$d501510a@iona.com>
To: "Paul Kiel" <paul@xmlhelpline.com>
Cc: <xmlschema-dev@w3.org>
Hi Paul,

I think the two statements are not actually in conflict if
you take the following two clauses into account. The trick is
that union memberType gets expanded immediately as per
4.1.2.3 so that you will never see union in the post-expansion
memberTypes, which 2.5.1.3 is talking about. Assuming that
observation is correct, you should be able to specify union
as a memberType of another union.

2.5.1.3 Union datatypes

[Definition:] The datatypes that participate in the definition of a
·union· datatype are known as the memberTypes of that ·union· datatype.

4.1.2.3 Derivation by union

If {variety} is union for any Simple Type Definition components
resolved to above, then the that Simple Type Definition is replaced
by its {member type definitions}.

-Takuki Kamiya



----- Original Message -----
From: Paul Kiel
To: Ashok Malhotra
Cc: xmlschema-dev@w3.org
Sent: Thursday, January 31, 2002 9:17 AM
Subject: Re: union of a union legal?

> Thanks so much for the help Ashok.  I did see that sentence and had
> a hard time reconciling it with the one from the spec in my original
email.
>
> 2.5.1.3 Union datatypes
> "Any number (greater than 1) of ·atomic· or ·list· ·datatype·s can
> participate in a ·union· type"
>
> 4.1.2.3 Derivation by union
> "A ·union· datatype can be ·derived· from one or more ·atomic·, ·list·
> or other ·union· datatypes, known as the ·memberTypes· of that ·union·
datatype."
>
> The latter clearly states (as I read it) the union of union is possible.
> The former seems to indicate it is not possible (but does not explicitly
> state it is not possible).  Given the conflict, I went with the latter
which
> seemed to me to be more specific.
>
> I am still not clear on which sentence to believe.
> My apologies for belaboring the point.
>
> Paul
>
Received on Friday, 1 February 2002 21:16:06 GMT

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