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XML Schema

XML Schema. 3 – 4 June 2004. www.eu-egee.org. EGEE is a project funded by the European Union under contract IST-2003-508833. Objectives. Development background xs:schema element General structure overall structure Annotations Defining elements Associating documents with schemas.

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XML Schema

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  1. XML Schema 3 – 4 June 2004 www.eu-egee.org EGEE is a project funded by the European Union under contract IST-2003-508833

  2. Objectives • Development background • xs:schema element • General structure • overall structure • Annotations • Defining elements • Associating documents with schemas Introduction to web services, 3-4 June 2004 - 2

  3. Development of Schema • Originally the tags in a XML document were defined in Document Type Definition (DTD) document. • This was not itself a XML document. • DTDs could be inline or separate documents. • DTDs did not inherently define namespaces • So schemas were developed which were XML documents, are separate from instances and namespaces were integral. Introduction to web services, 3-4 June 2004 - 3

  4. Reference to a Schema <?xml version="1.0"?> <note xmlns="http://www.nesc.ac.uk" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.nesc.ac.uk note.xsd"> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> Introduction to web services, 3-4 June 2004 - 4

  5. Simple Schema <?xml version="1.0"?> <xs:schema xmlns:xs=http://www.w3.org/2001/XMLSchema targetNamespace="http://www.nesc.ac.uk" xmlns="http://www.nesc.ac.uk" > <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="to" type="xs:string"/> <xs:element name="from" type="xs:string"/> <xs:element name="heading" type="xs:string"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> Introduction to web services, 3-4 June 2004 - 5

  6. Common Schema data types • xs:string • xs:decimal • xs:integer • xs:boolean • xs:date • xs:time Introduction to web services, 3-4 June 2004 - 6

  7. Defining Elements • Elements defined with element element • Name given by name attribute • Content and attributes given in two ways: • content of element element defines type • or type attribute refers to type <xs:element name="order"> <xs:complexType> ... </xs:complexType> </xs:element> <xs:element name="order" type="order" /> <xs:complexType name="order"> ... </xs:complexType> Introduction to web services, 3-4 June 2004 - 7

  8. Defining Text-Only Elements • Text-only elements have simple type • basic type is xs:string • also do numbers with xs:decimal • more simple data types later <xs:element name="surname" type="xs:string" /> <surname>Poe</surname> <xs:element name="price" type="xs:decimal" /> <price>24.99</price> Introduction to web services, 3-4 June 2004 - 8

  9. Defining Empty • Empty elements have complex type with no content <xs:element name="br"> <xs:complexType /> </xs:element> <br /> Introduction to web services, 3-4 June 2004 - 9

  10. Open Elements • Unconstrained elements are of type xs:anyType • default when no type is specified <xs:element name="description" /> <description> This can contain <emph>any</emph> content at all. </description> Introduction to web services, 3-4 June 2004 - 10

  11. Defining Element Values • Apply to Post-Schema-Validation Infoset (PSVI) • available to stage after validation • Values fixed on element definition • default attribute gives default <xs:element name="surname" type="xs:string" default="Doe" /> <surname /> Functionally equivalent <surname>Doe</surname> Introduction to web services, 3-4 June 2004 - 11

  12. Fixed attribute fixed attribute gives fixed (or null) value <xs:element name="surname" type="xs:string" fixed="Doe" /> <surname /> valid <surname>Doe</surname> valid <surname>Smith</surname> invalid Introduction to web services, 3-4 June 2004 - 12

  13. Missing Element Values • Element still validated even if has no value • only allowed if nillable is true • xsi:nil="true" used in instance <xs:element name="date-of-birth" type="xs:date" nillable="true"/> <date-of-birth>1972-05-30</date-of-birth> valid <date-of-birth /> invalid <date-of-birth xsi:nil="true"/> valid Introduction to web services, 3-4 June 2004 - 13

  14. Making an attribute optional • All attributes are optional by default. To explicitly specify that the attribute is optional, use the "use" attribute: • <xs:attribute name="lang" type="xs:string" use="optional“ /> • To make an attribute required: • <xs:attribute name="lang" type="xs:string" use="required“ /> Introduction to web services, 3-4 June 2004 - 14

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