XML Schema Basics, and Defining Simple Types - FIU SCIS

COP 4814

Florida International University
Kip Irvine

XML Schema Basics, and Defining
Simple Types

Updated: 2/23/2016
Based on Goldberg, Chapters 9 & 10

Irvine COP 4814

XML Schema Overview

• Also known as XML Schema Definition (XSD)
• Specifies the structure of valid XML documents

– defines a set of elements, their relationships to each
other, and the attributes that they can contain.

• Designed to address shortcomings of DTDs

– has a system of data types
– lets you define global and local elements
– likely to replace DTDs in the future as the standard

schema language

Latest info: http://w3.org/XML/Schema

Irvine COP 4814

Data Type Categories

• Atomic type

– XML element that only contains text

• List type

– collection of items

• Complex type

– XML element that contains child elements and/or
attributes

Irvine COP 4814

Sample XML File & Schema

<?xml version="1.0"?>
<wonder>

<name>Colossus of Rhodes</name>
<location>Greece</location>
<height>107</height>
</wonder>

<?xml version="1.0"?> incomplete Schema file

<element name="wonder">

<complexType>

<sequence>

<element name="name" type="string"/>

<element name="location" type="string"/>

<element name="height" type="string"/>

</sequence>

</complexType>

</element>

Irvine COP 4814

Complete Schema File

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<element name="wonder">
<complexType>
<sequence>
<element name="name" type="string"/>
<element name="location" type="string"/>
<element name="height" type="string"/>
</sequence>
</complexType>

</element>

</xs:schema>

Irvine COP 4814

Linking the XML Document

To the XML Schema file: Visual Studio doesn’t need this
extra line—you can just assign
<?xml version="1.0"?> a value to the Schemas
property of the XML file.

<wonder
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation="09-06.xsd" >

<name>Colossus of Rhodes</name>

<location>Greece</location>

<height>107</height>

</wonder> Web location, network
path, or local file

Irvine COP 4814

XML Annotations

Structured comments that can be processed by XML
parsers. Can appear anywhere, multiple times.

<xs:annotation>
<xs:documentation>
This XML Schema will be used to validate
documents from the student registration system.
</xs:documentation>

</xs:annotation>

Irvine COP 4814

Atomic Datatypes

• Contain a single value (cannot be divided).
• Based on one of the built-in types.

– Example: type="xs:string
• Restrictions can be included on their ranges and

character patterns, allowing you to create subtypes.
• Type categories:

– string, integer, boolean, date, decimal, etc.

Irvine COP 4814

Simple Types

Some of the more common types:

<xs:element name="height"
type="xs:string"/>

<xs:element name="year_built"
type="xs:integer"/>

<xs:element name="cost"
type="xs:decimal"/>

<xs:element name="is_standing"
type="xs:boolean"/>

<xs:element name="image"
type="xs:anyURI"/>

Web location, network
path, or local file

Irvine COP 4814

Irvine COP 4814

Standard Date/Time Formats

• xs:date:

yyyy-mm-dd "2005-04-26"

• xs:time:

hh:mm:ss "16:21:00"

• xs:dateTime

yyyy-mm-ddThh:mm:ss

"2005-04-26T16:21:00"

Irvine COP 4814

xs:duration

• xs:duration:

– PnYnMnDTnHnMnS

• 3 months, 4 days, 6 hours, 17 minutes:

– "P3M4DT6H17M"

• 90 days:

– "P90D"

• 4 days and 6 hours:

– "P4DT6H"

Irvine COP 4814

Other Date Types

Type Examples (April)
xs:gYear "1965" (April 1965)
xs:gMonth "--04" (April 26)
xs:gYearMonth "1965-04" (26th day)
xs:gMonthDay "--0426"
xs:gDay "---26"

Irvine COP 4814

Custom Type

• Identify the XML element you wish to define
• The "base" attribute identifies an existing type.
• Example: string of <= 1024 characters:

<xs:element name="story"> this custom type is
<xs:simpleType> anonymous
<xs:restriction base="xs:string">
<xs:length value="1024"/>
</xs:restriction>
</xs:simpleType>

</xs:element>

Irvine COP 4814

Named Custom Type

• Alternatively you can add a name attribute to the
xs:simpleType element:

<xs:element name="story">
<xs:simpleType name="story_type">
<xs:restriction base="xs:string">
<xs:length value="1024"/>
</xs:restriction>
</xs:simpleType>

</xs:element>

Irvine COP 4814

Applying a Custom Type

• The same named type can be used multiple times:

<xs:element name="story" type="story_type"/>
<xs:element name="summary" type="story_type"/>
<xs:element name="another_story" type="story_type"/>

Irvine COP 4814

Limiting Values to a Range

• Use xs:minInclusive and xs:maxInclusive:

<xs:element name="student_age">

<xs:simpleType>

<xs:restriction base="xs:integer">

<xs:minInclusive value="10">

<xs:maxInclusive value="120">

</xs:restriction>

</xs:simpleType>

</xs:element>

Also possible:
minExclusive, maxExclusive

Irvine COP 4814

Set of Possible Values

Use xs:enumeration

<xs:element name="student_level">
<xs:simpleType>

<xs:restriction base="xs:string">
<xs:enumeration value="undergraduate"/>
<xs:enumeration value="graduate"/>
<xs:enumeration value="unclassified"/>

</xs:restriction>
</xs:simpleType>
</xs:element>

Irvine COP 4814

Specifying an Exact Length

Example:

<xs:element name="panther_id">
<xs:simpleType>

<xs:restriction base="xs:string">

<xs:length value="7"/>

</xs:restriction>
</xs:simpleType>
</xs:element>

Irvine Also possible:
xs:minLength, xs:maxLength

COP 4814

Specifying a Matching Pattern

• Uses regular expression syntax
• Suppose the account_id element must contain

AB, followed by digits:

<xs:element name="account_id">
<xs:simpleType>

<xs:restriction base="xs:string">
<xs:pattern value="AB\d+"/>

</xs:restriction>
</xs:simpleType>
</xs:element>

Irvine COP 4814

Deriving a List Type

• When the XML file contains a list of values

– Example: dates when a student declared or
changed majors:

<xs:element name="catalog_dates"> this custom type is
<xs:simpleType> anonymous

<xs:list itemType="xs:date"/>

</xs:simpleType>
</xs:element>

Irvine COP 4814

Deriving a Named List Type

Use a named type if you plan to apply it more than
once.

<xs:simpleType name="dateList">
<xs:list itemType="xs:date"/>

</xs:simpleType>
.
<!-- create instances: -->
<xs:element name="catalog_dates"

type="dateList"/>
<xs:element name="enrollment_dates"

type="dateList"/>

Irvine COP 4814

Summary

• Use built-in types when you have no particular
restrictions on the values

• Use simple (atomic) derived types to control ranges
and lengths

• Use list types for repeated items
• Chapter 11 explains how to create complex types.

Irvine COP 4814