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eXtensible Markup LanguageLectu rer : Phan Vo Minh Than g MSc.

eXtensible Markup Language

XML Schemashttp://www.w3.org/TR/xmlschema-0/ (Primer)http://www.w3.org/TR/xmlschema-1/ (Structures)http://www.w3.org/TR/xmlschema-2/ (Datatypes)Thanks to Roger L. Costello

eXtensible Markup Language Phan Vo Minh Thang

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XML Lectures Notes XML Schemas

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< e s o 0 > < ate a > ectu es otes Sc e as

Purpose of XML Schemas (and DTDs)

Specify: the structureof instance documents

"this element contains these elements, which contains these other

elements, etc"

the datatypeof each element/attribute

"this element shall hold an integer with the range 0 to 12,000" (DTDsdon't do too well with specifying datatypes like this)

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Motivation for XML Schemas

People are dissatisfied with DTDs

It's a different syntax

You write your XML (instance) document using one syntaxand the DTD using another syntax --> bad, inconsistent

Limited datatype capability

DTDs support a very limited capability for specifyingdatatypes. You can't, for example, express "I want the element to hold an integer with a range of 0to 12,000"

Desire a set of datatypes compatible with those found indatabases

DTD supports 10 datatypes; XML Schemas supports

44+ datatypes

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Highlights of XML Schemas XML Schemas are a tremendous advancement over DTDs:

Enhanced datatypes

44+ versus 10

Can create your own datatypes

Example: "This is a new type based on the string type and elements ofthis type must follow this pattern: ddd-dddd, where 'd' represents a digit".

Written in the same syntax as instance documents less syntax to remember

Object-oriented'ish

Can extend or restrict a type (derive new type definitions on the basis of old ones)

Can express sets, i.e., can define the child elements to occur in any order

Can specify element content as being unique (keys on content) and uniquenesswithin a region

Can define multiple elements with the same name but different content

Can define elements with nil content

Can define substitutable elements - e.g., the "Book" element is substitutable for the

"Publication" element.

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Let's Get Started!

Convert the BookStore.dtd (next page) to the XMLSchema syntax

for this first example we will make a straight, one-to-one

conversion, i.e., Title, Author, Date, ISBN, and Publisher will holdstrings, just like is done in the DTD

We will gradually modify the XML Schema to use stronger types

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BookStore.dtd

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ATTLIST

ELEMENT

ID

#PCDATA

NMTOKEN

ENTITY

CDATA

BookStore

Book

Title

Author

Date

ISBNPublisher

This is the vocabulary that

DTDs provide to define yournew vocabulary

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element

complexType

schema

sequence

http://www.w3.org/2001/XMLSchema

string

integer

boolean

BookStore

Book

Title

Author

Date

ISBNPublisher

http://www.books.org (targetNamespace)

This is the vocabulary that

XML Schemas provide to define your

new vocabulary

One difference between XML Schemas and DTDs is that the XML Schema vocabulary

is associated with a name (namespace). Likewise, the new vocabulary that you

define must be associated with a name (namespace). With DTDs neither set of

vocabulary is associated with a name (namespace) [because DTDs pre-dated namespaces].

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BookStore.xsd (see example01)xsd = Xml-Schema Definition

(explanations on

succeeding pages)

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ISBN, Publisher)>

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All XML Schemas hav

"schema" as the rootelement.

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The elements anddatatypes that

are used to construct

schemas

- schema

- element

- complexType- sequence

- string

come from the

http:///XMLSchem

namespace

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element

complexType

schema

sequence

http://www.w3.org/2001/XMLSchema

string

integer

boolean

XMLSchema Namespace

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Indicates that the

elements defined

by this schema

- BookStore

- Book

- Title- Author

- Date

- ISBN

- Publisher

are to go in the

http://www.books.org

namespace

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BookStore

Book

Title

Author

Date

ISBNPublisher

http://www.books.org (targetNamespace)

Book Namespace (targetNamespace)

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This is referencing a

Book element declaration

The Book in what

namespace? Since there

is no namespace qualifier

it is referencing the Book

element in the default

namespace, which is the

targetNamespace! Thus,this is a reference to the

Book element declaration

in this schema.

The default namespace is

http://www.books.org

which is the

targetNamespace!

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This is a directive to any

instance documents which

conform to this schema:Any elements used by the

instance document which

were declared in this

schema must be namespace

qualified.

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Referencing a schema in an XMLinstance document

My Life and Times

Paul McCartney

July, 1998

94303-12021-43892

McMillin Publishing

...

1. First, using a default namespace declaration, tell the schema-validator that all of the elements

used in this instance document come from the http://www.books.org namespace.

2. Second, with schemaLocation tell the schema-validator that the http://www.books.org

namespace is defined by BookStore.xsd (i.e., schemaLocation contains a pair of values).

3. Third, tell the schema-validator that the schemaLocation attribute we are using is the one in

the XMLSchema-instance namespace.

1

2

3

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schemaLocationtype

noNamespaceSchemaLocation

http://www.w3.org/2001/XMLSchema-instance

nil

XMLSchema-instance Namespace

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Referencing a schema in an XML instance document

BookStore.xml BookStore.xsd

targetNamespace="http://www.books.org"schemaLocation="http://www.books.org

BookStore.xsd"

- defines elements in

namespace http://www.books.org

- uses elements from

namespace http://www.books.org

A schema defines a new vocabulary. Instance documents use that new vocabulary.

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Note multiple levels of checking

BookStore.xml BookStore.xsd XMLSchema.xsd

(schema-for-schemas)

Validate that the xml document

conforms to the rules described

in BookStore.xsd

Validate that BookStore.xsd is a valid

schema document, i.e., it conforms

to the rules described in theschema-for-schemas

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Default Value for minOccurs and maxOccurs

The default value for minOccurs is "1" The default value for maxOccurs is "1"

Equivalent!

Do Lab1

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Qualify XMLSchema, Default targetNamespace

In the first example, we explicitly qualified all elements from the XML Schemanamespace. The targetNamespace was the default namespace.

BookStore

Book

Title

Author

Date

ISBNPublisher

http://www.books.org (targetNamespace)http://www.w3.org/2001/XMLSchema

element

complexType

schema

sequence

string

integer

boolean

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Default XMLSchema,

Qualify targetNamespace Alternatively (equivalently), we can design our schema so that XMLSchema is

the default namespace.

BookStore

Book

Title

Author

Date

ISBNPublisher


element

complexType

schema

sequence

string

integer

boolean

h l "htt // 3 /2001/XMLS h "

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(see example02)

Note that

http:///XMLSchema

is the default

namespace.Consequently, there

are no namespace

qualifiers on

- schema

- element

- complexType

- sequence

- string

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Here we are

referencing aBook element.

Where is that

Book element

defined? In

what namespace?

The bk: prefix

indicates what

namespace this

element is in. bk:

has been set to

be the same as the

targetNamespace.

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bk: References the targetNamespace

BookStore

Book

Title

Author

Date

ISBNPublisher


bk

Do Lab1.1

element

complexType

schema

sequence

string

integer

boolean

Consequently, bk:Bookrefers to the Book element in the targetNamespace.

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Inlining Element Declarations

In the previous examples we declared an element andthen we refed to that element declaration. Alternatively,we can inlinethe element declarations.

On the following slide is an alternate (equivalent) way ofrepresenting the schema shown previously, using inlinedelement declarations.

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(see example03)

Note that we have moved

all the element declarations

inline, and we are nolonger ref'ing to the

element declarations.

This results in a much

more compact schema!

This way of designing the schema - by inlining everything - is called theRussian Doll design.

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Do Lab 2

(see example03)

Anonymous types (no name)

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yp

The following slide shows an alternate (equivalent)schema which uses a named complexType.

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(see example04)

Named typeThe advantage of

splitting out Book's

element declaration

and wrapping them

in a named type is

that now this type

can be reusedby

other elements.

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is equivalent to:

Element A references thecomplexType foo.

Element A has the

complexType definition

inlinedin the element

declaration.

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but not Both! An element declaration can have a type attribute, or a

complexType child element, but it cannot have both a typeattribute and a complexType child element.

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Summary of Declaring Elements (two

ways to do it)

A simple type

(e.g., xsd:string)or the name of

a complexType

(e.g., BookPublication)

1

2

A nonnegative

integer

A nonnegative

integer or "unbounded"

Note: minOccurs and maxOccurs can only

be used in nested (local) element declarations

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Defining the Date element to be of type string is unsatisfactory (it allows any

string value to be input as the content of the Date element, including non-datestrings).

We would like to constrain the allowable content that Date can have. Modify theBookStore schema to restrict the content of the Date element to just date values

(actually, year values. See next two slides).

Similarly, constrain the content of the ISBN element to content of this form: d-ddddd-ddd-d or d-ddd-ddddd-d or d-dd-dddddd-d, where 'd' stands for 'digit'

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A built-in datatype(i.e., schema validators know about this datatype)

This datatype is used to represent a specific day (year-month-day)

Elements declared to be of type date must follow this form: CCYY-MM-DD

range for CC is: 00-99

range for YY is: 00-99

range for MM is: 01-12

range for DD is:

01-28 if month is 201-29 if month is 2 and the gYear is a leap gYear

01-30 if month is 4, 6, 9, or 11

01-31 if month is 1, 3, 5, 7, 8, 10, or 12

Example: 1999-05-31 represents May 31, 1999

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A built-in datatype (Gregorian calendar year)

Elements declared to be of type gYear must follow this form: CCYY

range for CC is: 00-99

range for YY is: 00-99 Example: 1999 indicates the gYear 1999

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(see example05)

targetNamespace="http://www.books.org"

xmlns="http://www.books.org"

elementFormDefault="qualified">

Here we are defining a

new (user-defined) data-

type, called ISBNType.

Declaring Date to be of

type gYear, and ISBN to

be of type ISBNType

(defined above)

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< sd:s p e ype a e S N ype >

"I hereby declare a new type called ISBNType. It is a restricted form of

the string type. Elements declared of this type must conform to one of the following patterns:

- First Pattern: 1 digit followed by a dash followed by 5digits followed by another dash followed by 3 digits followed by

another dash followed by 1 more digit, or

- Second Pattern: 1 digit followed by a dash followed by 3

digits followed by another dash followed by 5 digits followed by

another dash followed by 1 more digit, or- Third Pattern: 1 digit followed by a dash followed by 2

digits followed by another dash followed by 6 digits followed by

another dash followed by 1 more digit."

These patterns are specified usingRegular Expressions. In a few slideswe will see more of the Regular Expression syntax.

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The vertical bar means "or"

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When do you use the complexType element and when doyou use the simpleType element?

Use the complexType element when you want to define childelements and/or attributes of an element

Use the simpleType element when you want to create a new typethat is a refinement of a built-in type (string, date, gYear, etc)

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Primitive Datatypes

string

boolean

decimal

float

double

duratio

dateTime

time

date

gYearMonth

gYear

gMonthDay

n

Atomic, built-in

"Hello World"

{true, false, 1, 0}

7.08

12.56E3, 12, 12560, 0, -0, INF, -INF, NAN

12.56E3, 12, 12560, 0, -0, INF, -INF, NAN

P1Y2M3DT10H30M12.3S

format: CCYY-MM-DDThh:mm:ss

format: hh:mm:ss.sss

format: CCYY-MM-DD

format: CCYY-MM

format: CCYY

format: --MM-DD

Note: 'T' is the date/time separatorINF = infinity

NAN = not-a-number

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Primitive Datatypes gDay

gMonth

hexBina

base64Binar

anyUR

QNam

NOTAT

ry

y

I

e

ION

Atomic, built-in format: ---DD(note the 3 dashes)

format: --MM

a hex string

a base64 string

http://www.xfront.com

a namespace qualified name

a NOTATION from the XML spec

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Derived types normalizedString

token

language

IDREFS

ENTITIES

NMTOKEN

NMTOKENS

Name

NCName

ID

IDREF

ENTITY

integer nonPositiveInteger

Subtype of primitive datatype A string without tabs, line feeds, or carriage returns

String w/o tabs, l/f, leading/trailing spaces,consecutive spaces

any valid xml:lang value, e.g., EN, FR, ...

must be used only with attributes




part (no namespace qualifier) must be used only with attributes



456

negative infinity to 0

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Built-in Datatypes (cont.)

Derived types

negativeInteger

long

int

short

byte

nonNegativeInteger

unsignedLong

unsignedInt

unsignedShort

unsignedByte

positiveInteger

Subtype of primitive datatype

negative infinity to -1

-9223372036854775808 to 9223372036854775807

-2147483648 to 2147483647

-32768 to 32767

-127 to 128

0 to infinity

0 to 18446744073709551615

0 to 4294967295

0 to 65535

0 to 255

1 to infinity

Do Lab 3Note: the following types can only be used with attributes (which we will discuss later):

ID, IDREF, IDREFS, NMTOKEN, NMTOKENS, ENTITY, and ENTITIES.

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A new datatype can be defined from an existing datatype (called the "base"

type) by specifying values for one or more of the optional facetsfor the basetype.

Example. The string primitive datatype has six optional facets:

length

minLength

maxLength

pattern

enumeration

whitespace (legal values: preserve, replace, collapse)

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Specifying Facet Values

1. This creates a new datatype called 'TelephoneNumber'.

2. Elements of this type can hold string values,3. But the string length must be exactly 8 characters long and

4. The string must follow the pattern: ddd-dddd, where 'd' represents a 'digit'.

(Obviously, in this example the regular expression makes the length facet

redundant.)

1

2

3

4

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This creates a new type called shape.

An element declared to be of this type

must have either the value circle, or triangle, or square.

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The integer datatype has 8 optional facets:

totalDigits

pattern

whitespace

enumeration

maxInclusive

maxExclusive

minInclusive

minExclusive

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This creates a new datatype called 'EarthSurfaceElevation'.

Elements declared to be of this type can hold an integer.However, the integer is restricted to have a value between

-1290 and 29035, inclusive.

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Facets:- length

- minlength

- maxlength

- pattern- enumeration

- minInclusive

- maxInclusive

- minExclusive

- maxExclusive...

Sources:

- string

- boolean

- number- float

- double

- duration

- dateTime

- time...

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"or" them together?

An element declared to be of type TelephoneNumber

must be a string of length=8 andthe string must

follow the pattern: 3 digits, dash, 4 digits.

An element declared to be of type shape

must be a string with a value ofeithercircle, or

triangle, orsquare.

Patterns, enumerations => "or" them together

All other facets => "and" them together

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Thus far we have created a simpleType using one of thebuilt-in datatypes as our base type.

However, we can create a simpleType that uses another

simpleType as the base. See next slide.

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This simpleType uses EarthSurfaceElevation as its base type.

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Sometimes when we define a simpleType we want to

require that one (or more) facet have an unchangingvalue. That is, we want to make the facet a constant.

simpleTypes which

derive from this

simpleType may

not change this

facet.

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Error! Cannot

change the valueof a fixed facet!

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Example. Create a schema element declaration for an elevation element.Declare the elevation element to be an integer with a range -1290 to 29035

5240

Here's one way of declaring the elevation element:

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Here's an alternative method for declaring elevation:

The simpleType definition is

defined inline, it is an anonymous

simpleType definition.

The disadvantage of this approach is

that this simpleType may not be

reused by other elements.

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ways to do it)

1

2

3

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g ,

for programs. Use for providing a comment to humans

Use for providing a comment to programs

The content is any well-formed XML

Note that annotations have no effect on schema validation

The following constraint is not expressible with XML Schema: The value of element A should be greater

than the value of element B. So, we need to use a separate tool (e.g., Schematron) to check this constraint.

We will express this constraint in the appinfo section (below).

A should be greater than B

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You cannot put annotations at just any random location in

the schema.

Here are the rules for where an annotation element cango:

annotations may occur before and after any global component

annotations may occur only at the beginning of non-global

components

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targetNamespace="http://www.books.org"

xmlns="http://www.books.org"


Can put

annotations

only at

theselocations

Suppose that you want to annotate, say, the Date element

declaration. What do we do? See next page ...

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g p p g

xmlns="http://www.books.org"elementFormDefault="qualified">

This is how to annotate the Date element!

Inline the annotation within the Date element declaration.

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In the previous example we showed

with no attributes. Actually, it can have two attributes:

source: this attribute contains a URL to a file which containssupplemental information

xml:lang: this attribute specifies the language that thedocumentation was written in

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Element

In the previous example we showed

with no attributes. Actually, it can have one attribute: source: this attribute contains a URL to a file which contains

supplemental information

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y p

Schemas.

Let's back up for a moment and look at XML Schemasfrom a "big picture" point of view.

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Code to check thestructure and content

(datatype) of the data

Code to actually

do the work

"In a typical program, up to 60% of the code is spent checking the data!"

- source unknown

Continued -->

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Code to check thestructure and content

of the data

Code to actually

do the work

If your data is structured asXML, and there is a schema,

then you can hand the

data-checking task off to a

schema validator.

Thus, your code is reduced

by up to 60%!!!

Big $$ savings!

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SupplierConsumer

P.O.

Schema

Validator

P.O.

Schema

Software

to Process

P.O.

"P.O. is

okay" P.O.

(Schema at third-party, neutral web site)

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Data Model

With XML Schemas you specify how your XML data will beorganized, and the datatypes of your data. That is, with XMLSchemas you model how your data is to be represented in an

instance document.

A Contract

Organizations agree to structure their XML documents in

conformance with an XML Schema. Thus, the XML Schemaacts as a contract between the organizations.

A rich source of metadata

An XML Schema document contains lots of data about the data in

the XML instance documents, such as the datatype of the data,the data's range of values, how the data is related to anotherpiece of data (parent/child, sibling relationship), i.e., XMLSchemas contain metadata

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validate your data (so that you don't have to write code to do it)

However, there are many other uses for XML Schemas. Schemas area wonderful source of metadata.

Truly, your imagination is the only limit on its usefulness.

On the next slide I show how to use the metadata provided by XMLSchemas to create a GUI. The slide after that shows how to

automatically generate an API using the metadata in XML Schemas.Following that is a slide showing how to create a "smart editor" usingXML Schemas.

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P.O.

SchemaGUI

BuilderP.O.

HTMLSupplier

Web

Server

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P.O.

SchemaAPI

BuilderP.O.

API

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P.O.

SchemaSmart Editor

(e.g., XML Spy)

Helps you build your

instance documents.

For example, it pops

up a menu showingyou what is valid next.

It knows this by looking

at the XML Schema!

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XML Schema

ValidateXML

documents

Automatic

GUI generationSemantic Web???

AutomaticAPI generation

Smart Editor

Do Lab 4

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Recall that the string datatype has a pattern facet.The value of a pattern facet is a regular expression.

Below are some examples of regular expressions:

Regular Expression

- Chapter \d- Chapter \d

- a*b

- [xyz]b- a?b

- a+b

- [a-c]x

Example

- Chapter 1- Chapter 1

- b, ab, aab, aaab,

- xb, yb, zb- b, ab

- ab, aab, aaab,

- ax, bx, cx

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[a-c]x

[-ac]x

[ac-]x [^0-9]x

\Dx

Chapter\s\d

(ho){2} there

(ho\s){2} there

.abc

(a|b)+x

ax, bx, cx

-x, ax, cx

ax, cx, -x any non-digit char followed by x

any non-digit char followed by x

Chapter followed by a blankfollowed by a digit

hoho there

ho ho there any (one) char followed by abc

ax, bx, aax, bbx, abx, bax,...

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a{1,3}x

a{2,}x

\w\s\w

ax, aax, aaax

aax, aaax, aaaax,

word character (alphanumericplus dash) followed by a spacefollowed by a word character

[a-zA-Z-[Ol]]* A string comprised of any

lower and upper case letters,except "O" and "l"

\. The period "." (Without the

backward slash the period means"any character")

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\t\\\|\-\^\?\*\+\{\}\[\]

tabThe backward slash \The vertical bar |The hyphen -The caret ^The question mark ?The asterisk *The plus sign +The open curly brace {The close curly brace }The open paren (

The close paren )The open square bracket [The close square bracket ]

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\p{Lu}

\p{Ll}

\p{N}

\p{Nd}

\p{P}

\p{Sc}

An uppercase letter, from any language

A lowercase letter, from any language

A number - Roman, fractions, etc

A digit from any language

A punctuation symbol

A currency sign, from any language

"currency sign from any

language, followed by one

or more digits from any

language, optionally

followed by a period andtwo digits from any

language"

$45.99

300

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[1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]

0 to 99 100 to 199 200 to 249 250 to 255

This regular expression restricts a string to have

values between 0 and 255. Such a R.E. might be useful in describing an

IP address ...

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Datatype for representing IP addresses. Examples,

129.83.64.255, 64.128.2.71, etc.

This datatype restricts each field of the IP address

to have a value between zero and 255, i.e.,

[0-255].[0-255].[0-255].[0-255]Note: in the value attribute (above) the regular

expression has been split over two lines. This is

for readability purposes only. In practice the R.E.

would all be on one line.

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Consider this XML document: (line break characters areexplicitly shown)

\r\n

\r\n

This is a \r\n

simple paragraph. What \r\n

do you think of it? \r\n

\r\n

When an XML parser reads in this document it

"normalizes" ALL line breaks. Thus, after normalizationthe XML document looks like this:

\n

\n

This is a \n

simple paragraph. What \ndo you think of it? \n

\n

Consequence: you don't have to be concerned about different

platforms using different line break characters since all XML

documents will have their line break characters normalized to \n

regardless of the platform. (So, if you're writing an XML

Schema regex expression you can simply use \n to indicate linebreak, regardless of the platform.)

2. The xml:space="preserve" attribute has no impact on line

break normalization.

3. Suppose that you want a line break character in your XMLdocument, other than \n. For example, suppose that you want \r

in your XML document. By default, it would get normalized to

\n. To prevent this, use a character reference:

Do Lab 5

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We can do a form of subclassing complexTypedefinitions. We call this "derived types"

derive by extension: extend the parent complexType withmore elements

derive by restriction: create a type which is a subset of thebase type. There are two ways to subset the elements:

redefine a base type element to have a restricted range ofvalues, or

redefine a base type element to have a more restricted number

of occurrences.

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< sd:co p e ype a e >

Note that

BookPublication extends

the Publication

type, i.e., we are doing

Derive by Extension

(see example06)

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Elements declared to be of type BookPublication will have 5 child elements - Title, Author,

Date, ISBN, and Publisher. Note that the elements in the derived type are appended to the

elements in the base type.

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Title

AuthorDate

ISBN

Publisher

Publication

BookPublication

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TitleAuthor

Date

BookPublication

ISBNPublisher

"extends"

Do Lab 6

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Elements of type SingleAuthorPublication will have 3 child elements - Title, Author, and Date.

However, there must be exactly one Author element.

Note that in the restriction type you must repeat all the declarations from the base type (except when

the base type has an element with minOccurs="0" and the subtype wishes to delete it. See next slide).

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Note that in this

subtype we haveeliminated the

Author element,

i.e., the subtype is

just comprised of

an unboundednumber of Title

elements followed

by a single Date

element.If the base type has an element with minOccurs="0", and the subtype wishes to

not have that element, then it can simply leave it out.

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I simply show the delta (i.e., show those declarations that are changed)?

What's the advantage of doing derived by restriction if I have to repeateverything? I'm certainly not saving on typing.

Answer:

Even though you have to retype everything in the base type there areadvantages to explicitly associating a type with a base type. In a few slideswe will see element substitution- the ability to substitute one element for

another. A restriction of element substitution is that the substitutingelement have a type that derives from the type of the element it issubstituting. Thus, it is beneficial to link the type.

Also, later we will see that an elements content model may be substitutedby the content model of derived types. Thus, the content of an elementthat has been declared to be of type Publication can be substituted with aSingleAuthorPublication content since SingleAuthorPublication derivesfrom Publication. We will discuss this type substitutabilityin detail later.

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, j ,derivations.

Rationale: "For example, I may create a complexType and make it publiclyavailable for others to use. However, I don't want them to extend it with

their proprietary extensions or subset it to remove, say, copyrightinformation." (Jon Cleaver)

Publication cannot be extended nor restricted

Publication cannot be restricted

Publication cannot be extended

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declaredare those that have a representation in an XML instancedocument.

You definecomponents that are used just within the schema document(s).

Schema components that are definedare those that have norepresentation in an XML instance document.

Declarations:

- element declarations

- attribute declarations

Definitions:

- type (simple, complex) definitions

- attribute group definitions- model group definitions

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ypchildren of

Local element declarations, local type definitions:

These are element declarations/type definitions that are nestedwithin other elements/types.

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Global type definition

Global element declaratio

Local element declarationsLocal type definition

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p p Answer: only global elements/types can be referenced (i.e.,

reused). Thus, if an element/type is local then it is effectively

invisible to the rest of the schema (and to other schemas).

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In Boston we use the words "T" and "subway" interchangeably.For example, "we took the T into town", or "we took the subwayinto town".

Thus, "T" and "subway" are substitutable. Which one is usedmay depend upon what part of the state you live in, what moodyou're in, or any number of factors.

We would like to be able to express this substitutability in XMLSchemas.

That is, we would like to be able to declare in a schema an element called

"subway", an element called "T", and state that "T"may be substituted for"subway". Instance documents can then use either or ,depending on their preference.

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g yhead element.

subway is the headelement

T is substitutable for subway

So what's the big deal?

- Anywhere a head element can be used in an instance document,

any member of the substitutionGroup can be substituted!

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q

Red Line

Instance doc:

Red Line

Alternative

instance doc

(substitute Tfor subway):

This example shows the element being substituted with

the element.

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is shown a Spanish version of the element.

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Red Line

Schema:

Instance doc:

Linea Roja

Alternative

instance doc(customized

for our

Spanish

clients):

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If the type of a substitutionGroup element is the same as the headelement then you can omit it (the type)

In our Subway example we could have omitted the type attribute in thedeclaration of the T element since it is the same as Subways type(xsd:string).

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This type must be the same as "xxx" or,

it must be derived from "xxx".

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PublicationType

BookType MagazineType

In order for Book and Magazine to be in a substitutionGroup with

Publication, their type (BookType and MagazineType, respectively)must be the same as, or derived from Publication's type (PublicationType)

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Illusions: The Adventures of a Reluctant Messiah

Richard Bach1977

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0-440-34319-4

Dell Publishing Co.

Natural Health

1999

The First and Last Freedom

J. Krishnamurti

1954

0-06-064831-7

Harper & Row

can contain any element in the substitutionGroup with Publication!

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q

Red Line

Instance doc:

Red Line

Not allowed!

Note: there is no error in declaring T to be substitutable with subway.

The error occurs only when you try to do substitution in the instance document.

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1. Transitive: if element A can substitute for element B, and element B can substitutefor element C, then element A can substitute for element C.

A --> B --> C then A --> C

2. Non-symmetric: if element A can substitute for element B, it is not the case that element Bcan substitute for element A.

Do Lab 7

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Category (autobiography | non-fiction | fiction) #REQUIRED

InStock (true | false) "false"

Reviewer CDATA " ">

BookStore.dtd

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(see example07)

InStock (true | false) "false"

Reviewer CDATA " "

Category (autobiography | non-fiction | fiction) #REQUIRED

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"Instance documents are required to have the Category attribute(as indicated by use="required"). The value of Category must be

either autobiography, non-fiction, or fiction (as specified by the

enumeration facets)."

Note: attributes can only have simpleTypes (i.e., attributes cannot

have child elements).

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required

optional

prohibited

The "use" attribute must be

optional if you use

default or fixed.

xsd:string

xsd:integer

xsd:boolean...

1

2

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When declaring a global attribute do not specify a "use"

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g y q

Local attribute declaration. Use the

"use" attribute here.

Global attribute declaration. Must NOT

have a "use" ("use" only makes sense in

the context of an element)

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attributeGroup.

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(see example08)

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y pthey are defined (nested) within.

"bar and boo are

attributes of foo"

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These attributesapply to the

element they are

nested within (Book)

That is, Book has three

attributes - Category,InStock, and Reviewer.

Do Lab 8.a,

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Example. Consider this:

5440

The elevation element has these two constraints:

- it has a simple (integer) content- it has an attribute called units

How do we declare elevation? (see next slide)

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yp g q

1. elevation contains an attribute.- therefore, we must use

2. However, elevation does not contain child elements (which is what we generally

use to indicate). Instead, elevation contains simpleContent.

3. We wish to extend the simpleContent (an integer) ...

4. with an attribute.

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Let's restrict elevation to hold an integer with a range 0 -

12,000 and let's restrict units to hold either the string "feet"or the string "meters"

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An alternative formulation of the above shapes example is to inline the simpleType definition:

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An alternate formulation of the above Person example is to create a named complexType and then use that type:

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Example. Large, green, sour

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X must be a complexType

Y must be a simpleType

versus

Do Lab 8.b,

8.c

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element declarations, no attribute declarations allowed!

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An example showing the use of the element

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...

Cannot inline the

group definition.

Instead, you must

use a refhere and

define the group

globally.

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xmlns= http://www.travel.org


(see example10)

Note: the choice is an exclusive-or, that is, transportation can contain

only one element - either train, or plane, or automobile.

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xmlns= http://www.binary.org


XML Schema:

Notes:

1. An element can fix its value, using the fixed attribute.2. When you don't specify a value for minOccurs, it defaults to "1".

Same for maxOccurs. See the last example (transportation) where

we used a element with no minOccurs or maxOccurs.

(see example 11)

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0

or equivalently:

red

or equivalently:

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XML Schema:

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p://www. . g


XML Schema:

means that Book must contain all five child elements, butthey may occur in any order.

(see example 12)

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The element cannot be nested within either ,

, or another

The contents of must be just elements. It cannot contain or

Do Lab 9

DTD:

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targetNamespace http://www.photography.org

xmlns="http://www.photography.org"


Schema:

Instance

doc (snippet):

Do Lab 10

(see example 13)

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Consequences of having no namespace

1. In the instance document dont namespace qualify the elements.

2. In the instance document, instead of using schemaLocation usenoNamespaceSchemaLocation.

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(see example14)

My Life and Times

Paul McCartney

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1998

1-56592-235-2

McMillin Publishing

(see example14)

1. Note that there is no default namespace declaration. So, none of the elements are

associated with a namespace.

2. Note that we do not use xsi:schemaLocation (since it requires a pair of values - a namespace

and a URL to the schema for that namespace). Instead, we use xsi:noNamespaceSchemaLocation.

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Validation can apply to the entire XML instance document,or to a single element.

My Life and TimesPaul McCartney

1998

1-56592-235-2

Macmillan Publishing

Validating against

two schemas

The elements are

defined in Book.xsd, and

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Richard Bach1977

0-440-34319-4

Dell Publishing Co.

The First and Last Freedom

J. Krishnamurti

19540-06-064831-7

Harper & Row

John Doe

123-45-6789

Sally Smith

000-11-2345

Library.xml

(see example 15)

defined in Book.xsd, and

the elementsare defined in Employee.xsd.

The , ,

and elements

are not defined in any schema!

1. A schema validator will

validate each Book element

against Book.xsd.

2. It will validate each

Employee element againstEmployee.xsd.

3. It will not validate the other

elements.

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xsv performs lax validation. Thus, it will accept the instance document on the previous

slide (but it will note validation="lax" in its output)

All the other validators do strict validation. Consequently, they will reject the instancedocument on the previous slide.

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schema (i.e., the schema that is doing the include)

The net effect of include is as though you had typed all the definitionsdirectly into the containing schema

LibraryBook.xsd LibraryEmployee.xsd

Library.xsd

d l T

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Library.xsd (see example 16)

These are

referencing

element

declarations

in the otherschemas.

Nice!

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p p

Chameleon components.

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Product.xsd (see example17)

Note that this schema has no targetNamespace!

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Company.xsd (see example17)

This schema s Product.xsd. Thus, the components in Product.xsd are namespace-coerced

to the company targetNamespace. Consequently, we can reference those components just as thoughthey had originally been declared in a schema with the same targetNamespace.

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Namespace

A

A.xsd

Namespace

B

B.xsd

C.xsd

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Camera.xsd

Nikon.xsd Olympus.xsd Pentax.xsd

Nikon.xsd

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targetNamespace= http://www.olympus.com

xmlns="http://www.olympus.com"


Olympus.xsd

Pentax.xsd

These import

elements give

us access to

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schemaLocation Olympus.xsd />

Camera.xsd (see example 18)

the componentsin these other

schemas.

Here I amusing the

body_type

that is

defined

in theNikon

namespac

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Nikon.xsd

http://www.olympus.com

Olympus.xsd

http://www.pentax.com

Pentax.xsd">

Ergonomically designed casing for easy handling

300mm

1.2

1/10,000 sec to 100 sec

Olympus, andPentax namespaces.

Camera.xml (see example 18)

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The next slide shows the non-redundant version.

Ergonomically designed casing for easy handling

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300mm

1.2

1/10,000 sec to 100 sec

Camera.xml (non-redundant version)

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Do Labs

11.a, 11.b,

11.c

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Example: For a document containing a Lottery drawing we might have

12 49 37 99 20 67

How do we declare the element Numbers ...

(1) To contain a list of integers, and

(2) Each integer is restricted to be between 1 and 99, and

(3) The total number of integers in the list is exactly six.

July 1

b 6 b

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21 3 67 8 90 12

July 8

55 31 4 57 98 22

July 15

70 77 19 35 44 11

Lottery.xml (see example19)

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Lottery.xsd

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Restrict the numbers to maxInclusive value="99"

d l th l "6"/

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Lottery.xsd (see example19)

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NumbersList is a list where the type of each item is OneToNinetyNine.LotteryNumbers restricts NumbersList to a length of six (i.e., an element

declared to be of type LotteryNumbers must hold a list of numbers,

between 1 and 99, and the length of the list must be exactly six).

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Alternatively,

This is read as: "We are creating a new type called LotteryNumbers.

It is a restriction. At this point we can either use the base

attribute or a simpleType child element to indicate the type that

we are restricting (you cannot use both the base attribute and the

simpleType child element). We want to restrict the type that is a

list of OneToNinetyNine. We will restrict that type to a length of 6."

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i.e., lists only apply to simpleTypes

In the instance document, you must separate each item in a list withwhite space (blank space, tab, or carriage return)

The only facets that you may use with a list type are:

length: use this to specify the length of the list

minLength: use this to specify the minimum length of the list

maxLength: use this to specify the maximum length of the list

enumeration: use this to specify the values that the list may have

pattern: use this to specify the values that the list may haveDo Lab 11.d

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simpleType 1 simpleType 2

simpleType 1+

simpleType 2

Note: you can create a union of more

than just two simpleTypes

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p

Cont. -->

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p yp

Cont. -->

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Y2KFamilyReunion.xsd (see example 20)

Mary

Pat

Patti

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Patti

Christopher

Elizabeth

Judy

PeterTom

Cheryl

Marc

JoeRoger

Y2KFamilyReunion.xml (see example 20)

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y

Version 2 of Y2KFamilyReunion.xsd (see example 21)

y

simpleTypes

The disadvantage of

creating the union

type in this manner

is that none of the

simpleTypes are

reusable.

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Alternatively,

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defined in the schema for schemas, but it gives you theidea of how the schemas-for-schemas might implement it)

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(see example22)

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2. simpleType that uses another simpleType as the base type:

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4. An alternate form of the above, where the list's datatype is specified using an inlined simpleType:

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6. An alternate form of the above, where the datatype UnboundedType is specified using an inline simpleType:

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Now an instance document author can optionally extend (after )

the content of elements with any element.

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SchemaRepository.xsd (see example23)

Suppose that the instance document author discovers this schema repository, and wants to extend

his/her elements with a element. He/she can do so! Thus, the instance

document will be extended with an element never anticipated by the schema author. Wow!

My Life and Times

Paul McCartney

199894303-12021-43892

P bli h M Milli P bli hi /P bli h

This instance document

uses components from

two different schemas.

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McMillin Publishing

Roger

Costello


Richard Bach

1977

0-440-34319-4

Dell Publishing Co.

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provided it's from the specified namespace

Note: you can specify a list of namespaces,

separated by a blank space. One of the

namespaces can be ##targetNamespace (seenext)

allows a new element,

provided it's from the namespace that the schema

is defining.

allows an element from any namespace. This is the default.

the new element must come from no namespace

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Now an instance document author can add any number of attributes onto a

element (as well as extend the element content).

/ d

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SchemaRepository.xsd (see example24)

Suppose that the instance document author discovers this schema, and wants to extend

his/her elements with an id attribute. He/she can do so! Thus, the instance document

will be extended with an attribute never anticipated by the schema author. Wow!

My Life and Times

Paul McCartney

1998

1-56592-235-2McMillin Publishing

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Roger

Costello


Richard Bach

1977

0-440-34319-4

Dell Publishing Co.

BookStore.xml (see example24)

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previous schemas where the content of all our elements werealways fixed and static.

We are empowering the instance document author with theability to define what data makes sense to him/her!

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from the specified namespace.

Note: you can specify a list of

namespaces, separated by a blank

space. One of the namespaces can be##targetNamespace (see next)

allows new attributes, provided they're from

the namespace that the schema is defining.

allows any attributes. This is the default.

allows any unqualified attributes (i.e., the attributes comes

from no namespace)

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p

...

after every element.

Further, it is allowing

for attribute expansion

on every element.

Truly, this is the ultimate

in openness!

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With this schema we are

allowing instance documents

to extend only at the end of

Book's content model.

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get information about these new capabilities to its vendors ASAP. Further, they will have little motivation

to wait for the next meeting of the cellphone community to consider upgrades to cellphone.xsd. They need

results NOW. How does open content help? That is described next.

Suppose that the cellphone schema is declared "open". Immediately NOKIA can extend its instance

documents to incorporate data about the new features. How does this change impact the vendor

applications that receive the instance documents? The answer is - not at all. In the worst case, the vendor's

application will simply skip over the new elements. More likely, however, the vendors are showing the

cellphone features in a list box and these new features will be automatically captured with the otherfeatures. Let's stop and think about what has been just described Without modifying the cellphone

schema and without touching the vendor's applications, information about the new NOKIA features has

been instantly disseminated to the marketplace! Open content in the cellphone schema is the enabler for

this rapid dissemination. Continued -->

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those vendors do not need to upgrade in lock-step

To wrap up this example suppose that several months later thecellphone community reconvenes to discuss enhancements to the

schema. The new features that NOKIA first introduced into the

marketplace are then officially added into the schema. Thuscompletes the cycle. Changes to the instance documents have driven

the evolution of the schema.

Do Lab 12

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relationships between the elements

Use of strong typing will capture much of the data content

The annotations can capture definitions and other explanatory information

The structure of the "definitions" will always be consistent with the structureused in the schema since they are linked

Since the schema itself is an XML document, we can use XSLT to extractthe annotations and transform the "semantic" information into a format

suitable for human consumption

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elements

Capture data semantics Use XML annotation element to capture

data definitionsUse data attributes to capture meta-data

Make data, meta-data and semanticsaccessible to a wide variety of clients

Use XSL to transform this XML taggeddata to make it readable to humans orother computers

Ensure parallelism between datastructure definition and data semantics

Consistency ensured by having both partof same XML schema

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Number of slides: 208 Updated date: 12/02/2006

Contact: Mr.Phan Vo Minh Thang([email protected])

05 - XML - Schemas

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