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Re: [xml-dev] Help regarding an XML attribute.
- From: Eddie Robertsson <eddie@allette.com.au>
- To: Vance Christiaanse <cintech@twcny.rr.com>
- Date: Wed, 17 Oct 2001 09:44:05 +1000
> > If the <complexContent> alternative is chosen, the type definition
> > ·resolved· to by the ·actual value· of the base [attribute] must be
> > a complex type definition;
>
> It now seems as though the definition earlier in this message is still
> incorrect and the following is correct:
>
> <xsd:complexType ...>
> <xsd:simpleContent> <!-- Change 1 of 2 -->
> <xsd:extension base="xsd:string">
> <xsd:attribute .../>
> </xsd:extension>
> </xsd:simpleContent> <!-- Change 2 of 2 -->
> </xsd:complexType>
>
> We all agree now that "extension" is correct and "restriction" is not
> correct.
>
> Do we also agree that "simpleContent" is correct and "complexContent" is not
> correct?
Well, I guess it depends on the use case but if the resulting type should have
simple content then you use xs:simpleContent (when you want to extend a simple
type by adding an attribute as in the above case). On the other hand if you want
the resulting type to be complex you use xs:complexType. Priscilla gave the
following example in a previous thread:
<xs:complexType name="base">
<xs:sequence>
<xs:element name="child"/>
</xs:sequence>
<xs:attribute name="attr1" type="xs:integer"/>
</xs:complexType>
<xs:complexType name="derived">
<xs:complexContent>
<xs:restriction base="base">
<xs:attribute name="attr1" type="xs:short" use="required" default="1"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
Cheers,
/Eddie
>
> Vance
>
> PS: I agree that both schemas below that XML Spy 4.0.1 accepted are, indeed,
> illegal.
>
> > -----Original Message-----
> > From: Eddie Robertsson [mailto:eddie@allette.com.au]
> > Sent: Monday, October 15, 2001 11:35 PM
> > To: Vance Christiaanse
> > Cc: Ronald Bourret; Wayne Steele; Huylanp@oceanwide.com;
> > xml-dev@lists.xml.org
> > Subject: Re: [xml-dev] Help regarding an XML attribute.
> >
> >
> > > an attribute element is allowed
> > > within either a restriction element or an extension element that is
> > > within either a simpleContent element or a complexContent
> > element that is
> > > within a complexType element. (At least that's how I read it.)
> >
> > Yes, an attribute element is allowed within a restriction element
> > but _only_
> > if the type in the base attribute resolves to a complex type.
> > The spec [1] reads:
> >
> > "If the <simpleContent> alternative is chosen, the type
> > definition ·resolved·
> > to by the ·actual value· of the base [attribute] must be either a
> > complex type
> > definition whose {content type} is a simple type definition or,
> > only if the
> > <extension> alternative is also chosen, a simple type definition;"
> >
> > This says that the type resolved to by the base attribute can only be a
> > simpleType if the extension alternative is chosen.
> >
> > > Both of the following are judged legal by XML Spy 4.0.1.
> > >
> > > In other words, I think my original schema is legal.
> >
> > I might be reading the spec wrong but I believe the schema below
> > is in error
> > and XML Spy is wrong.
> >
> > Cheers,
> > /Eddie
> >
> > [1]
> > http://www.w3.org/TR/xmlschema-1/#section-Constraints-on-XML-Repre
> > sentations-of-Complex-Type-Definitions
> >
> >
> >
> > > But I might agree that using simpleContent and extension is probably the
> > > most intuitive way to write this.
> > >
> > > <?xml version="1.0" encoding="UTF-8"?>
> > > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
> > > elementFormDefault="qualified" attributeFormDefault="unqualified">
> > > <xs:element name="myOuter">
> > > <xs:complexType>
> > > <xs:complexContent>
> > > <xs:restriction base="xs:string">
> > > <xs:attribute name="color" type="xs:string"/>
> > > </xs:restriction>
> > > </xs:complexContent>
> > > </xs:complexType>
> > > </xs:element>
> > > </xs:schema>
> > >
> > > <?xml version="1.0" encoding="UTF-8"?>
> > > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
> > > elementFormDefault="qualified" attributeFormDefault="unqualified">
> > > <xs:element name="myOuter">
> > > <xs:complexType>
> > > <xs:simpleContent>
> > > <xs:restriction base="xs:string">
> > > <xs:attribute name="color" type="xs:string"/>
> > > </xs:restriction>
> > > </xs:simpleContent>
> > > </xs:complexType>
> > > </xs:element>
> > > </xs:schema>
> > >
> > > > -----Original Message-----
> > > > From: Eddie Robertsson [mailto:eddie@allette.com.au]
> > > > Sent: Monday, October 15, 2001 7:57 PM
> > > > To: Vance Christiaanse
> > > > Cc: Ronald Bourret; Wayne Steele; Huylanp@oceanwide.com;
> > > > xml-dev@lists.xml.org
> > > > Subject: Re: [xml-dev] Help regarding an XML attribute.
> > > >
> > > >
> > > > > <xsd:complexType ...>
> > > > > <xsd:complexContent>
> > > > > <xsd:restriction base="xsd:string">
> > > > > <xsd:attribute .../>
> > > > > </xsd:restriction>
> > > > > </xsd:complexContent>
> > > > > </xsd:complexType>
> > > >
> > > > Not exactly. To create a text only content complex type with
> > one or more
> > > > attributes you must _extend_ a simple type. So, the correct definition
> > > > would be:
> > > >
> > > > <xsd:complexType ...>
> > > > <xsd:complexContent>
> > > > <xsd:extension base="xsd:string">
> > > > <xsd:attribute .../>
> > > > </xsd:extension>
> > > > </xsd:complexContent>
> > > > </xsd:complexType>
> > > >
> > > > Cheers,
> > > > /Eddie
> > > >
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Ronald Bourret [mailto:rpbourret@rpbourret.com]
> > > > > > Sent: Monday, October 15, 2001 2:20 PM
> > > > > > To: Wayne Steele
> > > > > > Cc: Huylanp@Oceanwide.com; xml-dev@lists.xml.org
> > > > > > Subject: Re: [xml-dev] Help regarding an XML attribute.
> > > > > >
> > > > > >
> > > > > > Wayne Steele wrote:
> > > > > > >
> > > > > > > >From: Huy-Lan Phan <Huylanp@Oceanwide.com>
> > > > > > > ... I think only a complex element can have attributes ...
> > > > > > >
> > > > > > > You are correct. Only a complex element can have attributes.
> > > > > >
> > > > > > But don't forget that a complex type can have simple content.
> > > > > >
> > > > > > <complexType>
> > > > > > <simpleContent>
> > > > > > <restriction base="xsd:string" />
> > > > > > </simpleContent>
> > > > > > <attribute>...</attribute>
> > > > > > ...
> > > > > > </complexType>
> > > > > >
> > > > > > -- Ron
> > > > > >
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