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Re: Enumeration component and restriction

From: Michael Marchegay <mmarcheg@optonline.net>
Date: Wed, 27 Aug 2003 16:00:54 +0200
Message-ID: <006d01c36ca3$a20d5e40$0302a8c0@esteban>
To: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
Cc: <xmlschema-dev@w3.org>

----- Original Message ----- 
From: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
To: "Michael Marchegay" <mmarcheg@optonline.net>
Cc: <xmlschema-dev@w3.org>
Sent: Wednesday, August 27, 2003 15:14
Subject: Re: Enumeration component and restriction


> "Michael Marchegay" <mmarcheg@optonline.net> writes:
>
> > I would like to have a clarification on the way to build the {value}
> > property of an enumeration component, and especially how those values
are
> > conveyed accross restrictions.
> >
> > For example, if a type (call it A) restricts a buil-in type by using
several
> > <enumeration> information item in the XML representation, and if another
> > type (call it B) restricts A by specifying some of the <enumeration>
> > information item specified in A, what components are in the {facets} of
A,
> > and what is its (their) value(s)?
>
> The set of all the [schema normalized value]s of the 'value'
> attributes of the <enumeration> children in the definition of B.
>
> > Example:
> > ---
> > <xs:simpleType name="A">
> >   <xs:restriction base="xs:token">
> >     <xs:enumeration value="x"/>
> >     <xs:enumeration value="y"/>
> >     <xs:enumeration value="z"/>
> >   </xs:restriction>
> > </xs:simpleType>
> >
> > <xs:simpleType name="B">
> >   <xs:restriction base="A">
> >     <xs:enumeration value="y"/>
> >   </xs:restriction>
> > </xs:simpleType>
> > ---
> >
> > Does the {facets} property of B contain:
> > 1 - One enumeration component whose {value} is {y}?
> > 2 - One enumeration component whose {value} is {x, y, z}?
> > 3 - Two enumeration components whose {value}s are {y} and {x, y, z}?
> >
> > XML Schema part. 2 - 4.3.5.3 makes me think that 3 would be the correct
> > answer...
>
> This section reads:
>
>   "If multiple <enumeration> element information items appear as
>   [children] of a <simpleType> the {value} of the enumeration
>   component should be the set of all such [value]s."
>
> I read that as saying the answer is (1), i.e. {y}.  How can you read
> it otherwise?

The definition of the {facets} property is:
---
{facets}
A set of facet components ·constituting a restriction· of the {facets} of
the {base type definition} with respect to a set of facet components
corresponding to the appropriate element information items among the
[children] of <restriction> (i.e. those which specify facets, if any), as
defined in Simple Type Restriction (Facets) (§3.14.3).
---

It says that Schema Representation Constraint: Simple Type Restriction
(Facets) shall by used for determining the {facets] property.

---
Schema Representation Constraint: Simple Type Restriction (Facets)
For a simple type definition (call it R) to restrict another simple type
definition (call it B) with a set of facets (call this S) all of the
following must be true:
[...]
3 The {facets} of R are the union of S and the {facets} of B, eliminating
duplicates. To eliminate duplicates, when a facet of the same kind occurs in
both S and the {facets} of B, the one in the {facets} of B is not included,
with the exception of enumeration and pattern facets, for which multiple
occurrences with distinct values are allowed.
---

3) uses the {facets} property of the base type definition, and says that
multiple occurence of a enumeration (I understand it as enumeration schema
component) are allowed with distinct values.

I deduce from it that a simple type definition can contain several
enumeration components in its {facets} property, and that the facets of the
enumeration component of the base type is added to the {facets} of the
derived type regardless of the presence of an enumeration component (built
from "local" <enumeration> information items, as described in 4.3.5.3).

I understand the last part of the last sentence as allowing multiple
enumeration *components*.  But it seems that in fact, it says that multiple
<enumeration> information items are allowed; those will be used for building
*one* enumeration component, that behaves just like other facet components
(it is overriden by the one defined locally within a restriction step).

Michael

>
> > And what for the following type?
> >
> > <xs:simpleType name="C">
> >   <xs:restriction base="A"/>
> > </xs:simpleType>
> >
> > Would it be one enumeration component with a {value} being {x, y, z}?
>
> Yes.
>
> ht
> -- 
>   Henry S. Thompson, HCRC Language Technology Group, University of
Edinburgh
>                       Half-time member of W3C Team
>      2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
>     Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
>      URL: http://www.ltg.ed.ac.uk/~ht/
>  [mail really from me _always_ has this .sig -- mail without it is forged
spam]
>
Received on Wednesday, 27 August 2003 10:00:57 GMT

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