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inquirydog 08-09-2004 04:01 AM

either/or elements in xml schema
 
I am trying to store my computer network information in an xml file,
and plan to write an xml schema for the file. The general format of
the xml should be like this

<networkinfo>
<ipaddress>1.2.3.4</ipaddress>
<hostname>qwerty</hostname>
<dnsserver>7.7.7.7</dnsserver>
</networkinfo>

The xml schema for this is simple (so simple that I won't
mention it). The problem is that on some computers, the network
information should be determined by dhcp, and all of the usual
information is not needed. In these cases the xml should look like
this

<networkinfo>
<dhcp />
</networkinfo>

I don't know how to write an xml schema that requires either n
elements (ie- ipaddress, hostname, and dnsserver), or a single
different element (ie- dhcp). I could bin the n elements in another,
and then use xsd:choice, although it seems a waste to add another tag
for this reason only.

I thank anyone in advance for suggestions.

thank
-I

ps- extra credit if you can extend this to describe an arbitrary
number of ethernet cards (eth0 ipaddress, eth1 ipaddress, etc.)

Helmut Dirtinger 08-09-2004 06:10 AM

Re: either/or elements in xml schema
 

"inquirydog" <inquirydog@hotmail.com> schrieb im Newsbeitrag
news:8063666c.0408082001.2b922083@posting.google.c om...
> I am trying to store my computer network information in an xml file,
> and plan to write an xml schema for the file. The general format of
> the xml should be like this
>
> <networkinfo>
> <ipaddress>1.2.3.4</ipaddress>
> <hostname>qwerty</hostname>
> <dnsserver>7.7.7.7</dnsserver>
> </networkinfo>
>
> The xml schema for this is simple (so simple that I won't
> mention it). The problem is that on some computers, the network
> information should be determined by dhcp, and all of the usual
> information is not needed. In these cases the xml should look like
> this
>
> <networkinfo>
> <dhcp />
> </networkinfo>
>
> I don't know how to write an xml schema that requires either n
> elements (ie- ipaddress, hostname, and dnsserver), or a single
> different element (ie- dhcp). I could bin the n elements in another,
> and then use xsd:choice, although it seems a waste to add another tag
> for this reason only.
>
> I thank anyone in advance for suggestions.
>
> thank
> -I
>
> ps- extra credit if you can extend this to describe an arbitrary
> number of ethernet cards (eth0 ipaddress, eth1 ipaddress, etc.)


Hi

as I understand the problem this should be a solution

The Schema:

<xs:schema elementFormDefault="qualified" attributeFormDefault="unqualified"
xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name="networkinfo" type="info"/>

<xs:complexType name="info" abstract="true"/>

<xs:complexType name="standardinfo">
<xs:complexContent>
<xs:extension base="info">
<xs:sequence>
<xs:element name="ipadress" type="xs:string"/>
<xs:element name="hostname" type="xs:string"/>
<xs:element name="dnsserver" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>

<xs:complexType name="dhcpinfo">
<xs:complexContent>
<xs:extension base="info">
<xs:sequence>
<xs:element name="dhcp" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
</xs:schema>

and a sampleinstance

<networkinfo xsi:type="standardinfo">
<ipadress/>
<hostname/>
<dnsserver/>
</networkinfo>

note that the schema uses three types: an abract info type and two types
(standardinfo and dhcpinfo) that extend the abstract type. the only element
is of typ info. For the instance document this means that you have replace
the type of the element by one of the none abstact subtypes. (with the
xsi:type attribute). An Instance of dhcpinfo would look like:

<networkinfo xsi:type="dhcpinfo">
<dhcp/>
</networkinfo>

greetings

hd



Priscilla Walmsley 08-09-2004 12:34 PM

Re: either/or elements in xml schema
 
Hi,

You could also do something simpler using xsd:choice, like:

<xs:element name="networkinfo" type="info"/>
<xs:complexType name="info">
<xs:choice>
<xs:sequence>
<xs:element name="ipadress" type="xs:string"/>
<xs:element name="hostname" type="xs:string"/>
<xs:element name="dnsserver" type="xs:string"/>
</xs:sequence>
<xs:element name="dhcp" type="xs:string"/>
</xs:choice>
</xs:complexType>

Hope that helps,
Priscilla
-----------------------------------------------------
Priscilla Walmsley
Author, Definitive XML Schema (Prentice Hall PTR)
http://www.datypic.com
-----------------------------------------------------

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