Validation – XML Schemas

Nguyễn Đăng Khoa

Content

• Document Type Definitions (DTDs)• XML Schemas

XML Schemas (XSD)

• Define XML vocabularies and grammars• Describe the structure and content of XML

documents in more detail than DTDs• XML Schema 1.0 specifications were first

published by the W3C in 2001, with a second edition following in 2004

• XML Schema 1.1 became a W3C Recommendation in April 2012

XSD’s goals

• Check XML document is valid or not

XSD – Benefits

• Are created using basic XML• Fully support the Namespace Recommendation• Validate text element content based on built-in

and user-defined data types• Create complex and reusable content models• Enable the modeling of programming concepts

such as object inheritance and type substitution

XSD 1.0 - Specifications

• Part 1: Structures (http://www.w3.org/TR/xmlschema-1/)

• Part 2: Datatypes (http://www.w3.org/TR/xmlschema-2/)

XSD - Example

XSD – Namespace in XSD & XML

XSD – Explicitly namespace

XSD – Default namespace

XSD – XML doesn’t use namespace

URI to xsd

XSD – XML uses namespace

XSD – XML uses namespace

URI to xsdnamespace blank

XSD – XML uses namespace

XSD – XML uses namespace

XSD – Element and Attribute qualification

XSD – qualified vs. unqualified

qualified

unqualified

XSD – Global vs. Local

GlobalLocal

XSD – Global vs. Local

• Global declarations are declarations that appear as direct children of the <schema> element. Global element declarations can be reused throughout the XML Schema.

• Local declarations do not have the <schema> element as their direct parent and can be used only in their specific context.

XSD – elementFormDefault

• qualified: nested elements must belong to the target namespace of the schema

• unqualified is default value, a mix of qualified and unqualified elements

XSD – elementFormDefault – Example

Valid

XSD – elementFormDefault – Example

Invalid

Element 'first': This element is not expected. Expected is ({http://www.example.com/name}first)

XSD – elementFormDefault – Example

Valid

XSD – elementFormDefault – Example

Invalid

Element '{http://www.example.com/name}first': This element is not expected. Expected is (first)

XSD – attributeFormDefault – Example

• Is same elementFormDefault• unqualified is default value

XSD – attributeFormDefault – Example

Valid

XSD – attributeFormDefault – Example

Invalid

XSD – attributeFormDefault – Example

Invalid

XSD – Content Models

• Is allowable content (type) of elements and attributes

• There are 2 content models– <complexType>– <simpleType>

XSD - <complexType>

• Defines types that contain attributes or elements

• There are 3 ways of interpreting a list of elements– <sequence>: Elements must appear in the given

order– <choice>: Only one of the elements in the list may

appear– <all>: Elements can appear in any order, with each

child element occurring zero or one time

XSD – <complexType> – Example

XSD – <complexType> – Example

XSD – Rule of <all>

• The <all> declaration must be the only content model declaration that appears as a child of a <complexType> definition

• The <all> declaration can contain only <element> declarations as its children – No <sequence>, <choice>, <group> in it

• The <all> declaration’s children may appear once each in the instance document

XSD - <element>

XSD - <element> – Name

XSD - <element> – Type

XSD - <element> – Local Type

include the type declaration as a child of the element declaration

XSD - <element> – Global Type

XSD - <element> – Cardinality

XSD - <element> – Cardinality

Default: 1

XSD - <element> – Default value

XSD - <element> – Fixed value

XSD – Mixed Content

• Enable you to include both text and element content within a single content model

XSD – Simple Content

• Enable you to include only text within a single content model

XSD – Empty Content

XSD – Elements Wildcards

• Suppose you want to specify that your element can contain any of the elements declared in your namespace, or any elements from another namespace

XSD – Elements Wildcards

List of namespace URIs

XSD – Elements Wildcards

indicate that any element from the schema’s target namespace can be used

XSD – Elements Wildcards

indicate that elements not in any namespace can be used

XSD – Elements Wildcards

indicate that all elements from any namespace or no namespace are allowed

XSD – Elements Wildcards

indicate that elements from namespaces other than the schema’s target namespace can be used

XSD – Elements Wildcards

(Default) Elements represented by this <any> element must be declared. Furthermore, the element must be valid according to its declaration

XSD – Elements Wildcards

Elements represented by this <any> element need not be declared in the schema and need not be valid even if they are declared

XSD – Elements Wildcards

Elements represented by this <any> element must be validated if they are declared, but must not be validated if they are declared

XSD – Elements Wildcards – Rules

• The <any> declaration can appear only within a content model. • You are not allowed to create global <any> declarations

XSD – <group>

• Enable you to define reusable groups of elements

XSD – Exercise - No namespace

XSD – Exercise – Use namespace

XSD - <attribute>

XSD - <attributeGroup>

• Enable you to define reusable groups of attributes

XSD – Built-in Data Types

XSD – Built-in Data Types

XSD – Built-in Data Types

XSD – Built-in Data Types

XSD – Built-in Data Types

XSD – Built-in Data Types

• In addition to the types listed, the XML Schema Recommendation also allows the types defined within the XML Recommendation– ID– IDREF– IDREFS– ENTITY– ENTITIES– NOTATION– NMTOKEN– NMTOKENS

XSD – Exercise

XSD – User-Defined Data Types

• When you declare a <simpleType>, you must always base your declaration on an existing data type– Built-in– Custom

• <simpleType> definitions are often called derived types. There are three primary derived types:– Restriction types– List types– Union types

XSD – User-Defined Data Types

prevent a simple type from being subtyped

XSD – Restriction Type

• is a subset of its base type

Facet

XSD – Restriction Type – Constraining Facets

Constraint Description

enumeration Defines a list of acceptable values

fractionDigits Specifies the maximum number of decimal places allowed. Must be equal to or greater than zero

length Specifies the exact number of characters or list items allowed. Must be equal to or greater than zero

maxExclusive Specifies the upper bounds for numeric values (the value must be less than this value)

maxInclusive Specifies the upper bounds for numeric values (the value must be less than or equal to this value)

maxLength Specifies the maximum number of characters or list items allowed. Must be equal to or greater than zero

minExclusive Specifies the lower bounds for numeric values (the value must be greater than this value)

minInclusive Specifies the lower bounds for numeric values (the value must be greater than or equal to this value)

minLength Specifies the minimum number of characters or list items allowed. Must be equal to or greater than zero

pattern Defines the exact sequence of characters that are acceptable

totalDigits Specifies the exact number of digits allowed. Must be greater than zero

whiteSpace Specifies how white space (line feeds, tabs, spaces, and carriage returns) is handled

Ref: http://www.w3schools.com/schema/schema_facets.asp

XSD – List Type

• create a list of items

XSD – Union Type

• allow potential values for elements and attributes to have any of several types

XSD – Union Type