XML Schemas

1. XML Schemas J. Pontes November 15, 2004

2. Schemas • Defines what a set of one or more document can look like. • What elements it contains, order, content, and attributes. • These documents are written in XML Schema language

3. DTD Disadvantages compared to XML • Cannot be parsed by an XML parser • All declarations in DTD are global (impossible to define two elements with same name.) • DTD cannot control what kind of information a given element or attribute can contain.

4. What XML Schema Buys You • One can define both global elements (used same way all along document) and local elements (particular meaning in a particular context). • XML Schemas contain a system of data types. • Gives more control over XML document

5. Schema: types of content • Simple Type – text only • Complex Types – contain other elements or attributes.

6. Simple Type • Date • Integer • String • Customer built types • In DTD we used #OCDATA to capture a name, a date or practically anything.

7. Complex Type • Describe the structure of a document, rather than content. • Complex Types • Elements that contain elements • Elements that contain element and text • Elements that contain only text • Elements that are empty • Each may contain attributes

8. Examples of Built-in Simple Types <xsd:element name=“weight” type=“xsd:string”/> <xsd:element name=“population” type=“xsd:integer” />

9. Custom Simple Type <xsd:simpleType name=“zipcodeType”> <xsd:restriction base=“xsd:string”> <xsd:pattern value=“\d{5}(-\d{4}?” /> </xsd:restriction> <xsd:simpleType> This type limits the content of elements (zipcodeType) to a string with 5 digits, an optional hyphen and 4 extra digits.

10. Complex Type Definition <xsd:complexType name=“endType”> <xsd:sequence> <xsd:element name=“animal” type=“animalType” minOccurs=“1” maxOccurs=“unbounded”/> </xsd:sequence> <xsd:complexType> Defines endType. It contains another element animal defined with another complex type animalType to define a particular element

11. Local end Global declarations • Global • Declared at top level of a schema, just immediately below xsd:schema element. They are available to be used throughout the the rest of the schema. • Global element declaration do not determine where an element can appear in the XML document – they only determine what the element will look like. • A global element declaration must be explicitly referenced in order to have it appear in a corresponding XML document. • Simple • Locally declared elements. Limited to the complex type definition in which they are declared and may not not be used elsewhere in the schema. • Such locally declared elements are automatically referenced.

12. Example of Local and Global Elements <?xml version=“1.0”?> <xsd:schema smlns:xsd=“http://www.w3.org/2000/10/XMLSchema> <xsd:element name=“endanged_species” type=“endType”/> <xsd:element name=“name” type=“xsd:string”/> <xsd:complexType name=“endType”> <xsd:sequence> <xsd:element name=“animal”> <xsd:complexType> <xsd:sequence> <xsd:element ref=“name” minOccurs=“2”/> <xsd:element name=“source” type=“sourceType”/> … </xsd:complexType> automatically referenced. manually referenced. Same name different definitions.

13. Cont’d <xsd:complexType name=“habitatType”> <xsd:sequence> <xsd:element name=“river”> <xsd:complexType> <xsd:sequence> <xsd:element ref=“name” minOccurs=“1” maxOccurs=“unbounded”/> <xsd:element name=“source” type=“xsd:string”/> … </xsd:complexType> … Same name different definitions.

14. Beginning a Simple Schema <?xml version=“1.0”?> //Declaring XML <xsd:schema xmlns:xsd=“ http://www.w3.org/2000/10/XMLSchema ” • Any element or type that is prefixed with xsd: will be recognized as coming from namespace* • Schema rules go in this space. </xsd:schema> • Save you schema as a text only with the .xsd extension.

15. Indicating a Location <?xml version=“1.0”?> <endanged_species xmlns:xsd=“http://www.w3.org/2000/10/XMLSchema-instance ” xsi:noNamespaceSchemaLocation= “ http://www.cookwook.com/ns/end_species/end_species.xsd ”> * * file.xsd previously created.

16. Making Schemas Annotations <?xml version=“1.0”?> <xsd:schema xmlns:xsd=“ http://www.w3.org/2000/10/XMLSchema ” <xsd:annotation> <xsd:documentation> This schema will be used to validate the set of XML documents for the Endangered Species Project. </xsd:documentation> </xsd:annotation>

17. Defining Simple Types • When declaring an element, you choose its name and what kind of content it should contain. • xsd:string – string of characters • xsd:decimal – decimal number • xsd:boolean – true of false • xsd:date – CCYY-MM-DD • xsd:time - • xsd:uriReference - element will contain an URL • xsd:language – two letter language listed in ISO639 • Custom – name of a custom simple type. • Code.xsd <xsd:elementname="weight" type="xsd:string" /> <xsd:elementname="population" type="xsd:integer" /> • Code.xml <weight>500 pounds</weight> <population>28</population> When a value is an integer or a string?

18. More XML Data Types • Click Here for More Data Types

19. Date and Time Data Types • Code.xsd <xsd:element name=“gestation” type=“xsd:timeDuration”/> (represent a certain amount of time) • Code.xml <gestation>P3M15D</gestation> (PnYnMnDTnHnMnS) n - non negative Period T begins optional time section

20. Date and Type Data Types • Code.xsd xsd:element name=“bedtime” type=“xsd.time:/> • Code.xml <bedtime>20:15:05-05:00>/bedtime>

21. Additional xsd:time • xsd:time (hh:mm:ss.sss) • xsd:timeInstant (CCYY-MM-DDTh:mm:ss.sss) • xsd:date CCYY-MM-DD • xsd:month (CCYY-MM • xsd:year (CCYY) • xsd:century (CC) • xsd:recurringDate • xsd:recurringDay

22. Number Type • xsd:decimal • xsd:integer • xsd:positiveinteger • xsd:negativeinteger • xsd:float • xsd:double

23. XML Validator • STG XML Validation