XSD / XSCHEMA Problem

[N.stolwijk]

I'm new to writing scheme.

And I'm breaking my teeth on this obviously easy one.
I would like to write a scheme which validates the following

<projects>
<project>
<id>text</id>
<name>text</name>
</project>
<project>
<name>text</name>
</project>
<project>
<id>text</id>
</project>
</projects>

But does not validate the following

<projects>
<project>
</project>
</projects>

Thus either the tag <id> or the tag <name> or both should be present.
The absence of both should result in non validation.

Thanx for the help,
I have already browsed lots of postings but couldn't find one which
could help me
Niko Stolwijk

[lluismf]

Your example generates this schema:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xs:element name="projects">
<xs:complexType>
<xs:sequence>
<xs:element maxOccurs="unbounded" ref="project"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="project">
<xs:complexType>
<xs:sequence>
<xs:element minOccurs="0" ref="id"/>
<xs:element minOccurs="0" ref="name"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="id" type="xs:NCName"/>
<xs:element name="name" type="xs:NCName"/>
</xs:schema>

The minOccurs restriction applies to individual elements, you cannot
make cross-element validations (in your case a logical OR). I'm afraid
XSD is not still powerful enough to do things like that.

Cheers
Lluis

[George Bina]

What you want is
(id, name) | id | name
As this is ambiguous content (when the parser encounters id it cannot
decide if it should follow the (id, name) or the id model) you need to
write it in a non ambiguous way (XML Schema does not accept ambiguos
content) and that can be done as follows:

(id, name?) | name

That means either id optionally followed by name or name.

In XML Schema notation that will be:
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element ref="id"/>
<xs:element minOccurs="0" ref="name"/>
<xs:sequence>
<xs:element ref="name"/>
</xs:choice>
</xs:complexType>

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com

[N.stolwijk]

Thanks for the schema.

I'm sad it's not possible to write it the way I would like it. So I have
decided to make an annotation in the schema. :-(

I have found simmilar solutions like yours, but they all allow the
absence of both tags, which I wanted to prevent.
Niko Stolwijk

Your example generates this schema:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xs:element name="projects">
<xs:complexType>
<xs:sequence>
<xs:element maxOccurs="unbounded" ref="project"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="project">
<xs:complexType>
<xs:sequence>
<xs:element minOccurs="0" ref="id"/>
<xs:element minOccurs="0" ref="name"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="id" type="xs:NCName"/>
<xs:element name="name" type="xs:NCName"/>
</xs:schema>

The minOccurs restriction applies to individual elements, you cannot
make cross-element validations (in your case a logical OR). I'm afraid
XSD is not still powerful enough to do things like that.

Cheers
Lluis

[N.stolwijk]

Thanks for the schema.

I'm sad it's not possible to write it the way I would like it. So I have
decided to make an annotation in the schema. :-(

I have found simmilar solutions like yours, but they all allow the
absence of both tags, which I wanted to prevent.
Niko Stolwijk

What you want is
(id, name) | id | name
As this is ambiguous content (when the parser encounters id it cannot
decide if it should follow the (id, name) or the id model) you need to
write it in a non ambiguous way (XML Schema does not accept ambiguos
content) and that can be done as follows:

(id, name?) | name

That means either id optionally followed by name or name.

In XML Schema notation that will be:
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element ref="id"/>
<xs:element minOccurs="0" ref="name"/>
<xs:sequence>
<xs:element ref="name"/>
</xs:choice>
</xs:complexType>

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com

[Lluis]

George's solution works fine !
I have to study a bit more :-)

[jammypac]

If you don't care about the order id and name are listed you could use
the following:

<xs:complexType>
<xs:choice minOccurs="1" maxOccurs="2">.
<xs:element ref="id"/>
<xs:element ref="name"/>
</xs:choice>
</xs:complexType>

This at least prevents empty content. Unfortunately it would allow for
id followed by id, or name followed by name.

-Jammy