W3C home > Mailing lists > Public > xmlschema-dev@w3.org > December 2002

RE: Newbie question

From: Vineet Chaoji <chaoji@roguewave.com>
Date: Sun, 29 Dec 2002 21:33:37 -0800
Message-ID: <F888C30C3021D411B9DA00B0D0209BE804DBE48F@cvo-exchange.cvo.roguewave.com>
To: "'Jeni Tennison'" <jeni@jenitennison.com>
Cc: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>

Thanks Jeni, for the detailed response. I have one enhancement to my
question.
Does to answer to my questions change if I add the clause that the base and
derived complex types are in different target namespaces as follows:

<xsd:schema targetNamespace="Alma/CommonEntity"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ent="Alma/CommonEntity"
elementFormDefault="qualified" attributeFormDefault="unqualified"
version="1">
      ...................

	<xsd:complexType name="EntityT">
		<xsd:attribute name="entityTypeName"
type="ent:EntityTypeNameT" use="required"/>
	</xsd:complexType>
</xsd:schema>


<xsd:schema targetNamespace="Alma/ObsProject" xmlns:prj="Alma/ObsProject"
xmlns:ent="Alma/CommonEntity" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified"
version="1">

   ......
	<xsd:complexType name="ObsProjectEntityT">
		<xsd:complexContent>
			<xsd:restriction base="ent:EntityT">
				<xsd:attribute name="entityTypeName"
type="ent:EntityTypeNameT" use="required" fixed="ObsProject"/>
			</xsd:restriction>
		</xsd:complexContent>
	</xsd:complexType>
</xsd:schema>

Looking at the specs it seems that your answers assumed that both the
complex types are in the same target namespace. But I dont understand how
does the target namespace influence the answer to my questions. In context
of my schema, I think, that the derived complex type should have the
use="required" irrespective of what its target namespace is.

Am I wrong? And if I am, why?

Thanks,
Vineet

-----Original Message-----
From: Jeni Tennison [mailto:jeni@jenitennison.com]
Sent: Sunday, December 29, 2002 8:56 AM
To: Vineet Chaoji
Cc: 'xmlschema-dev@w3.org'
Subject: Re: Newbie question


Hi Vineet,

> Consider the following complexTypes
>
> <xsd:complexType name="EntityT">
>   <xsd:attribute name="entityTypeName" type="ent:EntityTypeNameT"
> use="required"/>
> </xsd:complexType>
>
> <xsd:complexType name="ObsProjectEntityT">
>   <xsd:complexContent>
>       <xsd:restriction base="ent:EntityT">
>          <xsd:attribute name="entityTypeName" type="ent:EntityTypeNameT"
> fixed="ObsProject"/>
>       </xsd:restriction>
>   </xsd:complexContent>
> </xsd:complexType>
>
> ObsProjectEntityT restricts EntityT.
> Now my question is whether it is necessary to have the use="required" in
> ObsProjectEntityT when it puts constraints on the attribute
entityTypeName.
>
> Is it that attributes ('use' in this case) not defined in the restricting
> complexType are assumed to be picked from the base complexType?

No. The derived complex type either inherits the entire attribute
declaration or overrides the attribute declaration completely [1]; it
does not inherit individual attributes.

> As per my understanding, the derived complexType should represent a
> subset of the base complexType and the absence of use="required"
> (which implies use="optional") in the derived complexType violates
> this rule.

That is correct. [2] states that either the base attribute use must
not be required or the restricted attribute use must be required, so
in this case, since the attribute use in the base type is required the
corresponding attribute use in the restricted type must also be
required. In other words you need use="required" on the attribute
declaration in the derived complex type.

Cheers,

Jeni

[1] http://www.w3.org/TR/xmlschema-1/#c-add1
[2] http://www.w3.org/TR/xmlschema-1/#c-rad

---
Jeni Tennison
http://www.jenitennison.com/
Received on Monday, 30 December 2002 00:35:23 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 11 January 2011 00:14:35 GMT