Re: [xml-dev] Schema definition of element with optional children

[George Cristian Bina <george@oxygenxml.com>]

Hi Joe,

There are a couple of possibilities. One is to use xsi:type in the 
instance document to specify if you have a deleted or inserted, etc. 
address. A sample schema and instance document look like below

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
   elementFormDefault="qualified">
   <xs:element name="address" type="addressType"> </xs:element>
   <xs:complexType name="addressType" abstract="true"/>
   <xs:complexType name="inserted">
     <xs:complexContent>
       <xs:extension base="addressType">
         <xs:sequence>
           <xs:element ref="addressLine1"/>
           <xs:element ref="addressLine2"/>
           <xs:element ref="city"/>
           <xs:element ref="postCode"/>
           <xs:element ref="country"/>
         </xs:sequence>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>

   <xs:complexType name="deleted">
     <xs:complexContent>
       <xs:extension base="addressType"/>
     </xs:complexContent>
   </xs:complexType>

   <xs:element name="addressLine1">
     <xs:complexType/>
   </xs:element>
   <xs:element name="addressLine2">
     <xs:complexType/>
   </xs:element>
   <xs:element name="city">
     <xs:complexType/>
   </xs:element>
   <xs:element name="postCode">
     <xs:complexType/>
   </xs:element>
   <xs:element name="country">
     <xs:complexType/>
   </xs:element>
</xs:schema>

<address xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; 
xsi:type="inserted">
  <addressLine1/>
  <addressLine2/>
  <city/>
  <postCode/>
  <country/>
</address>

<address xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; 
xsi:type="deleted"/>

Another possibility is to declare the address element abstract and make 
two elements, for instance insertedAddress and deletedAddress that can 
substitute address. For that change the

<xs:element name="address" type="addressType" abstract="true"/>

from the above schema with:

<xs:element name="address" type="addressType" abstract="true"/>
   <xs:element name="insertedAddress" type="inserted" 
substitutionGroup="address"/>
   <xs:element name="deletedAddress" type="deleted" 
substitutionGroup="address"/>

and in that case the sample instances will look like:

<insertedAddress>
  <addressLine1/>
  <addressLine2/>
  <city/>
  <postCode/>
  <country/>
</insertedAddress>


<deletedAddress/>


If you want to keep the instance exactly as it is then you can use 
Schematron embedded rules, below there is a sample schema and instances.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"; 
elementFormDefault="qualified">
   <xs:element name="address">
     <xs:annotation>
       <xs:appinfo>
         <pattern xmlns="http://www.ascc.net/xml/schematron"; 
name="testAddress">
           <rule context="address[@recordStatus='deleted']">
             <assert test="count(*)=0">Deleted address should have no 
content.</assert>
           </rule>
         </pattern>
       </xs:appinfo>
     </xs:annotation>
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="addressLine1"/>
         <xs:element ref="addressLine2"/>
         <xs:element ref="city"/>
         <xs:element ref="postCode"/>
         <xs:element ref="country"/>
       </xs:sequence>
       <xs:attribute name="recordStatus" use="required">
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="inserted"/>
             <xs:enumeration value="deleted"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:attribute>
     </xs:complexType>
   </xs:element>
   <xs:element name="addressLine1">
     <xs:complexType/>
   </xs:element>
   <xs:element name="addressLine2">
     <xs:complexType/>
   </xs:element>
   <xs:element name="city">
     <xs:complexType/>
   </xs:element>
   <xs:element name="postCode">
     <xs:complexType/>
   </xs:element>
   <xs:element name="country">
     <xs:complexType/>
   </xs:element>
</xs:schema>


<address recordStatus="inserted">
  <addressLine1/>
  <addressLine2/>
  <city/>
  <postCode/>
  <country/>
</address>

<address recordStatus="deleted"/>

for an invalid instance like:

<address recordStatus="deleted">
  <addressLine1/>
  <addressLine2/>
  <city/>
  <postCode/>
  <country/>
</address>

you will get

SystemID: C:\george\workspace\oXygen\samples\test.xml
Location: 1:0
Description: Deleted address should have no content. (count(*)=0)

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


Joe Fawcett wrote:
> Dear All
> 
> I'm struggling to find the best way to restrict an element that holds 
> address data.
> If the address is to be deleted it will look like this:
> <address recordStatus="deleted"/>
> 
> if it's new or an update it will be along the lines of:
> 
> <address recordStatus="inserted">
>  <addressLine1></addressLine1>
>  <addressLine2></addressLine2>
>  <city></city>
>  <postCode></postCode>
>  <country></country>
> </address>
> 
> with various fields being optional, these are UK addresses only.
> 
> What's the most efficient way to declare this using XSD only as I 
> believe I can't say, "if recordStatus = 'deleted' then..." etc?
> 
> I believe I have to give a choice of two types but this seems tedious?
> 
> Thanks
> 
> Joe
> 
> 
> 
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