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RE: using xsd:choice + element value

From: Matt Long <mlong@phalanxsys.com>
Date: Mon, 27 May 2002 06:35:54 -0500
To: "'Eddie Robertsson'" <erobertsson@allette.com.au>
Cc: <xmlschema-dev@w3.org>
Message-ID: <000f01c20572$ab5266b0$3cfff6d0@gulag>
Eddie,

Hmmmmm...

The primary issue is that a schema needs to implement a 'choice' based
on a prior element 'value'.   The animal schema below illustrates the
point that the qualifier value of "dog | cat" cannot qualify the choice
elements (dogName | catName).  In other words the schema is valid with

	<animalType>cat</animal>
	<dogName>Scooby</dogName>

which is not the intent and therefore is not properly communicated.  Is
this simply not possible???

<xsd:simpleType name="qualifier">
	<xsd:enumeration value="dog"/>
	<xsd:enumeration value="cat"/>
</xsd:simpleType>

<xsd:element name="animal" type="animalType"/>

<xsd:complexType name="animalType">
	<xsd:sequence>
		<xsd:element name="animalQualifier" type="qualifier"/>
		<xsd:choice>
			<xsd:element name="dogName" type="xsd:string"/>
			<xsd:element name="catName" type="xsd:string"/>
		</xsd:choice>
	</xsd:sequence>
</xsd:complexType>

> -----Original Message-----
> From: Eddie Robertsson [mailto:erobertsson@allette.com.au]
> Sent: Sunday, May 26, 2002 7:11 PM
> To: mlong@phalanxsys.com
> Cc: xmlschema-dev@w3.org
> Subject: Re: using xsd:choice + element value
> 
> Hi Matt,
> 
> No, you can't do that using the design you have in your schema.
However,
> if I understand your problem correct I think you can use the technique
> of using xsi:type in the instance document to specify which type an
> element should use from the instance document. Here is a modified
> version of your schema where complexTypes are used instead of groups:
> 
> <xsd:element name=”whatIsIt” type=”baseType”/>
> 
> <!-- Empty type that is used as a common base for personType and
> placeType -->
> <xsd:complexType name="baseType"/>
> 
> <!-- Type defining the person -->
> <xsd:complexType name=”personType”>
>     <xsd:complexContent>
>         <xsd:extension base="baseType">
>             <xsd:sequence>
>                 <xsd:element name=”firstName” type=”xsd:string”/>
>                 <xsd:element name=”lastName” type=”xsd:string”/>
>             </xsd:sequence>
>         </xsd:extension>
>     </xsd:complexContent>
> </xsd:complexType>
> 
> <!-- Type defining the place -->
> <xsd:complexType name=”placeType”>
>     <xsd:complexContent>
>         <xsd:extension base="baseType">
>             <xsd:sequence>
>                 <xsd:element name=”country” type=”xsd:string”/>
>                 <xsd:element name=”city” type=”xsd:string”/>
>             </xsd:sequence>
>         </xsd:extension>
>     </xsd:complexContent>
> </xsd:complexType>
> 
> Note that the whatIsIt element have the type baseType. Also, I have
> removed you qualifier element because instead of using an element to
> qualify which type is used we're going to use xsi:type in the instance
> to specify which of the derived types the whatIsIt element has. E.g.
> 
> <whatIsIt xsi:type="personType">
>     <firstName>aaa</firstName>
>     <lastName>bbb</lastName>
> </whatIsIt>
> 
> This will only validate the whatIsIt element if it has subelements
> matching the personType. The same applies for the placeType:
> 
> <whatIsIt xsi:type="placeType">
>     <country>aaa</country>
>     <city>bbb</city>
> </whatIsIt>
> 
> Is this something that would fit your requirement?
> 
> Cheers,
> /Eddie
> 
> 
> > Is it possible to utilize ‘choice’ from an element value (not purely
> > the existence of the element name)
> >
> > Example: a schema with a qualifier (1=person, 2=place)…so the
question
> > is how can one determine the group ref from the element value of
> > ‘qualifier’ element (or is it simply not possible)?
> >
> > -Matt Long
> >
> > Phalanx Systems, LLC
> >
> > <xsd:element name=”whatIsIt” type=”z:infoType”/>
> >
> > <xsd:complexType name=”infoType”>
> >
> > <xsd:sequence>
> >
> > <xsd:element name=”qualifier” type=”z:myQualType”/>
> >
> > <!—how can ‘qualifier’ qualify the choice of group reference 
> >
> > <xsd:choice>
> >
> > <xsd:group ref=”z:personGroup”/>
> >
> > <xsd:group ref=”z:placeGroup”/>
> >
> > </xsd:choice>
> >
> > </xsd:sequence>
> >
> > </xsd:complexType>
> >
> > <xsd:group name=”personGroup”>
> >
> > <xsd:sequence>
> >
> > <xsd:element name=”firstName” type=”xsd:string”/>
> >
> > <xsd:element name=”lastName” type=”xsd:string”/>
> >
> > </xsd:sequence>
> >
> > </xsd:group>
> >
> > <xsd:group name=”placeGroup”>
> >
> > <xsd:sequence>
> >
> > <xsd:element name=”country” type=”xsd:string”/>
> >
> > <xsd:element name=”city” type=”xsd:string”/>
> >
> > </xsd:sequence>
> >
> > </xsd:group>
> >
> > <xsd:simpleType name=”myQualType”>
> >
> > <xsd:restriction base=”xsd:string”>
> >
> > <xsd:enumeration value=”1”/>
> >
> > <xsd:enumeration value=”2”/>
> >
> > </xsd:restriction>
> >
> > </xsd:simpleType>
> >
Received on Monday, 27 May 2002 08:10:00 UTC

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