XML Schema

1
XML Schema

• Leonidas Fegaras

2
XML Schema

• Replaces DTD
• Object-Oriented schemas
• Richer set of basic types
• Better ways of deriving new type declarations
  from old ones
• type extension
• type restriction
• Database-style key concept
• Uses namespaces
• Compatible with other standards

3
Base Types

• string, float, double, decimal, boolean
• timeDuration
• P10Y1M5T1H20M5S 10years1month5days1hour20'5'
  '
• binary
• uriReference
• QName
• ID, IDref
• A basic type may have properties, called facets
• length, minLength, maxLength
• minInclusive, maxInclusive, minExclusive,
  maxExclusive
• enumeration for string
• pattern for string
• encoding for binary (eg, base64)

4
Predefined Derived Types

• Derived by restrictions on facets
• ltxsdsimpleType name'integer' basexsddecimal'gt
• ltscale value'0'gt
• lt/xsdsimpleTypegt
• or multiplied in lists
• ltxsdsimpleType name'IDREFS' base'xsdIDREF'
  derivedBy'xsdlist'/gt
• Other built-in derived types
• Name
• int
• long
• short
• byte
• positiveInteger

5
Defining Simple Types

• Enumeration
• ltxsdsimpleType name'animal' base'xsdstring'gt
• ltxsdenumeration value'dog'/gt
• ltxsdenumeration value'cat'/gt
• lt/xsdsimpleTypegt
• Range restriction
• ltxsdsimpleType name'employeeAge'
  base'xsdpositiveInteger'gt
• ltxsdminInclusive value'18'/gt
  ltxsdmaxInclusive value'70'/gt
• lt/xsdsimpleTypegt
• Pattern
• ltxsdsimpleType name'ssn' base'xsdstring'gt
• ltxsdpattern value'\d3-\d2-\d4'gt
• lt/xsdsimpleTypegt
• List
• ltxsdsimpleType name'animals' base'animal'
  derivedBy'xsdlist'/gt

6
Elements

• Example
• ltxsdelement name'employee'gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name'name' type'xsdstring'/gt
• ltxsdelement name'address' type'xsdstring'/gt
• ltxsdelement name'ssn' type'ssn'/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• It corresponds to the DTD
• lt!ELEMENT employee (name,address,ssn)gt
• lt!ELEMENT name (PCDATA)gt
• lt!ELEMENT address (PCDATA)gt
• lt!ELEMENT ssn (PCDATA)gt

7
Element Attributes

• Element attributes can only appear inside
  xsdcomplexType in an xsdelement
• ltxsdattribute name'ssn' type'ssn'
  use'required'/gt
• ltxsdattribute name'father' type'xsdstring'
  use'optional'/gt
• Keys can be defined using XPath expressions
• ltxsdkey name'ssn'gt
• ltxsdselectorgtdept/personlt/xsdselectorgt
• ltxsdfieldgt_at_ssnlt/xsdfieldgt
• lt/xsdkeygt
• the selector defines the applicable elements
• the field defines the data that are unique
  withing the applicable elements
• xsdunique may be used to define unique
  combination of values
• Foreign keys are like IDRefs, but well-typed
• ltxsdkeyref refer'ssn'gt
• ltxsdselectorgtdept/personlt/xsdselectorgt
• ltxsdfieldgt_at_motherlt/xsdfieldgt
• ltxsdkeyrefgt

8
Other Specifiers of xsdelement

• Other attributes of xsdelement
• minOccurs minimum number of occurrences
• default '1'
• maxOccurs maximum number of occurrences
• default '1' if minOccurs is not given
• default '' otherwise
• optional is when minOccurs'0' and maxOccurs1'
• nullable 'true'
• ref 'type-name'
• Other attributes of xsdcomplexType
• content 'empty'
• content 'mixed'
• content 'elementOnly'
• derivedBy 'extension'
• derivedBy 'restriction'

9
xsdcomplexType

• Any content
• ltxsdanygt
• Concatenation (A1, A2, ..., An)
• ltxsdsequencegt A1 A2 ... An lt/xsdsequencegt
• Alternation (A1 A2 ... An)
• ltxsdchoicegt A1 A2 ... An lt/xsdchoicegt
• All but in any order (A1 A2 ... An)
• ltxsdallgt A1 A2 ... An lt/xsdallgt

10
Using xsdcomplexType

• ltxsdsimpleType name'state' base'xsdstring'gt
• ltxsdenumeration value'TX'gt
• ltxsdenumeration value'CA'gt
• lt/xsdsimpleTypegt
• ltxsdsimpleType name'zip' base'xsdstring'gt
• ltxsdpattern value'\d5'gt
• lt/xsdsimpleTypegt
• ltxsdcomplexType name'Address'
  content'elementOnly'gt
• ltxsdsequencegt
• ltxsdelement name'name' type'xsdstring'/gt
• ltxsdelement name'street'
  type'xsdstring'/gt
• ltxsdelement name'state' type'state'/gt
• ltxsdelement name'zip' type'zip'/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• ltxsdelement name'PurchaseOrder'gt
• ltxsdcomplexType content'elementOnly'gt
• ltxsdsequencegt
• ltxsdelement name'From' type'Address'/gt

11
Reusing Types

• Extending types
• ltxsdcomplexType name'GraduateStudent'
  base'Student' derivedBy'extension'gt
• ltxsdelement name'gpa' type'xsdpositiveInt
  eger'/gt
• lt/xsdcomplexTypegt
• Restricting types
• ltxsdsimpleType name"SKU"gt
• ltxsdrestriction base"xsdstring"gt
• ltxsdpattern value"\d3-A-Z2"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt

12
Using Schemas

• Schema po.xsd
• ltschema xmlns"http//www.w3.org/2001/XMLSchema"gt
• ltelement name'PurchaseOrder'gt
• ltcomplexType content'elementOnly'gt
• ...
• lt/complexTypegt
• lt/elementgt
• lt/schemagt
• Using targetNamespace
• ltschema xmlns"http//www.w3.org/2001/XMLSchema"
• xmlnspo"http//lambda.uta.edu/PO"
• targetNamespace"http//lambda.uta.edu/PO"
  gt
• ltelement name'PurchaseOrder'gt
• ltcomplexType content'elementOnly'gt
• ...
• lt/complexTypegt
• lt/elementgt
• lt/schemagt
• XML data that conforms to this XML Schema