But Roger, why not
<xs:sequence>
<xs:element name="Title" type="xs:string"/>
<xs:choice>
<xs:element name="ISBN" type="xs:string"/>
<xs:element name="Edition" type="xs:string"/>
</xs:choice>
</xs:sequence>
Greetings, Frank
Hi Folks,
This XML Schema choice:
<xs:choice>
<xs:sequence>
<xs:element name="Title" type="xs:string"/>
<xs:element name="ISBN" type="xs:string"/>
</xs:sequence>
<xs:sequence>
<xs:element name="Title" type="xs:string"/>
<xs:element name="Edition" type="xs:string"/>
</xs:sequence>
</xs:choice>
results in this error:
Title and Title violate "Unique Particle Attribution".
During validation against this schema, ambiguity
would be created for those two particles.
The branches of a choice cannot start with the same element name.
Suppose, for whatever reason, you need the choices to start with the Title element, what to do?
Here's a hack: Create a base complexType and for each branch of the choice create a subtype:
<xs:complexType name="Publication" abstract="true" />
<xs:complexType name="BookPublication">
<xs:complexContent>
<xs:extension base="Publication">
<xs:sequence>
<xs:element name="Title" type="xs:string"/>
<xs:element name="ISBN" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="MagazinePublication">
<xs:complexContent>
<xs:extension base="Publication">
<xs:sequence>
<xs:element name="Title" type="xs:string"/>
<xs:element name="Edition" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
Declare an element with the base type, Publication, as its type:
<xs:element name="Item" type="Publication"/>
In an XML instance document, if you want the <Item> element to hold book data (Title, ISBN), do this:
<Item xsi:type="BookPublication">
<Title>...</Title>
<ISBN>...</ISBN>
</Item>
If you want the <Item> element to hold magazine data (Title, Edition), do this:
<Item xsi:type="MagazinePublication">
<Title>...</Title>
<Edition>...</Edition>
</Item>
TaDa!
/Roger
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