Restrictions on a Set of Values To limit the content of an XML element to a set of acceptable values, we would use the enumeration constraint.

<xs:restriction base="xs:string"> <xs:enumeration value="Audi"/> <xs:enumeration value="Golf"/> <xs:enumeration value="BMW"/> </xs:restriction>

type="carType"/>

<xs:simpleType name="carType">

the type "carType" can be used by other elements

series of numbers or letters that can be used, we would use the pattern constraint.

<xs:minLength value="5"/> <xs:maxLength value="8"/>

<xs:pattern value="male|female"/>

The whiteSpace constraint is set to "preserve", which means that the XML processor WILL NOT remove any white space characters:

<xs:whiteSpace value="preserve"/>

The whiteSpace constraint is set to "replace", which means that the XML processor WILL REPLACE all white space characters (line feeds, tabs, spaces, and carriage returns) with spaces:

<xs:whiteSpace value="replace"/>

<xs:length value="8"/>

<xs:restriction base="xs:string"> <xs:pattern value="[a-z]"/>

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

<xs:complexType name="fullpersoninfo"> <xs:complexContent> <xs:extension base="personinfo">

Attributes are optional by default. To specify that the attribute is required, use the "use" attribute: <xs:attribute name="lang" type="xs:string" use="required"/>

targetNamespace="http://www.w3schools.com" indicates that the elements defined by this schema (note, to, from, heading, body.) come from the "http://www.w3schools.com" namespace.

xmlns:xs="http://www.w3.org/2001/XMLSchema" indicates that the elements and data types used in the schema come from the "http://www.w3.org/2001/XMLSchema" namespace.

This attribute has two values. The first value is the namespace to use. The second value is the location of the XML schema to use for that namespace

xmlns="http://www.w3schools.com" indicates that the default namespace is "http://www.w3schools.com".

Referencing a Schema in an XML Document

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3schools.com note.xsd"

prefixed with xs:

You don't have to learn a new language You can use your XML editor to edit your Schema files You can use your XML parser to parse your Schema files You can manipulate your Schema with the XML DOM You can transform your Schema with XSLT

XML Schemas are Extensible

Reuse your Schema in other Schemas Create your own data types derived from the standard types Reference multiple schemas in the same document

Well-Formed is not Enough

XML Schema became a W3C Recommendation 02. May 2001.

CDATA Everything inside a CDATA section is ignored by the parser.

A CDATA section starts with "<![CDATA[" and ends with "]]>":

<h:table xmlns:h="http://www.w3.org/TR/html4/">

<f:table xmlns:f="http://www.w3schools.com/furniture">

xmlns:namespace-prefix="namespaceURI"

Note that the address used to identify the namespace is not used by the parser to look up information. The only purpose is to give the namespace a unique name.

Uniform Resource Identifier (URI) A Uniform Resource Identifier (URI) is a string of characters which identifies an Internet Resource. The most common URI is the Uniform Resource Locator (URL) which identifies an Internet domain address.

not so common type of URI is the Universal Resource Name (URN)

Default Namespaces Defining a default namespace for an element saves us from using prefixes in all the child elements.

<table xmlns="http://www.w3.org/TR/html4/">

XML was designed to describe data and to focus on what data is. HTML was designed to display data and to focus on how data looks.

XML was created to structure, store and to send information.

It is just pure information wrapped in XML tags

XML tags are not predefined. You must "invent" your own tags. The tags used to mark up HTML documents and the structure of HTML documents are predefined.

XML allows the author to define his own tags and his own document structure.

XML will be used to describe the data, while HTML will be used to format and display the same data

XML is a cross-platform, software and hardware independent tool for transmitting information.

Use of Elements vs. Attributes Data can be stored in child elements or in attributes.

Should you avoid using attributes? Some of the problems with using attributes are: attributes cannot contain multiple values (child elements can) attributes are not easily expandable (for future changes) attributes cannot describe structures (child elements can) attributes are more difficult to manipulate by program code attribute values are not easy to test against a Document Type Definition (DTD) - which is used to define the legal elements of an XML document

Try to use elements to describe data. Use attributes only to provide information that is not relevant to the data.