- From: Costello, Roger L. <costello@mitre.org>
- Date: Tue, 8 Mar 2011 09:36:53 -0500
- To: "xmlschema-dev@w3.org" <xmlschema-dev@w3.org>
Hi Folks, Here is an example of using xsd:choice. The content of <transportation> is a choice of either <train>, <plane>, or <automobile>. <xsd:element name="transportation"> <xsd:complexType> <xsd:choice> <xsd:element name="train" type="xsd:string"/> <xsd:element name="plane" type="xsd:string"/> <xsd:element name="automobile" type="xsd:string"/> </xsd:choice> </xsd:complexType> </xsd:element> Rather than using xsd:choice, the schema could be designed using xsd:sequence. The sequence consists of an element that ref's to an abstract mode-of-transportation element. The train, plane, and automobile elements are globally declared and are substitutable with mode-of-transportation. <xsd:element name="transportation"> <xsd:complexType> <xsd:sequence> <xsd:element ref="mode-of-transportation" /> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="mode-of-transportation" abstract="true" type="xsd:string" /> <xsd:element name="train" substitutionGroup="mode-of-transportation"/> <xsd:element name="plane" substitutionGroup="mode-of-transportation"/> <xsd:element name="automobile" substitutionGroup="mode-of-transportation"/> I believe that the two designs produce identical results. Suppose the xsd:choice element were jettisoned from the XML Schema specification. Would there be any loss of functionality? Put another way, can you provide a real-world, compelling example of a schema that uses xsd:choice which cannot be expressed using abstract element plus substitution groups? /Roger
Received on Tuesday, 8 March 2011 14:37:28 UTC