XML Schemadefinition

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Modul 2:

XML Schemadefinition

a.Univ.-Prof. Dr. Werner Retschitzegger

Vorlesun g IFS in der B ioinfo rmati k SS 20 11

Johannes Kepler University Linz

www.jku.ac.at

Johannes Kepler University Linz

www.jku.ac.at Institute of Bioinformatics www.bioinf.jku.at Institute of Bioinformatics www.bioinf.jku.at

IFS

Information Systems Group

www.ifs.uni-linz.ac.at

IFS

Information Systems Group

www.ifs.uni-linz.ac.at M2-2 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Outline

Introduction

z Motivation for XML

z Document Markup Languages

z Application Areas for XML

XML 1.0 Namespaces XML Schema

The following slides are based (among others) on:

Elliotte Rusty Harold, W. Scott Means, XML in a Nutshell: A Desktop Quick Reference, 3rd Edition, O'Reilly & Associates, 2005

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M2-3

Motivation for XML

1/5

From HTML to XML

"If I invent another programming language,

its name will contain the letter

X

."

(N. Wirth, Software Pioniere Konferenz, Bonn 2001)

223 Mio. SQL 252 Mio. ABC 20,6 K “Werner Retschitzegger” 237 Mio. Soccer 603 Mio. XML 2,2 Mrd. Love Google Indicator: ... as of Sep/16/08 M2-4 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Motivation for XML

2/5

From HTML to XML

Brian Kerningham: "The problem with HTML-WYSIWYG is that

what you see is all you've got"

HTML (HyperText Markup Language) is the "Lingua Franca"

for representing Hypertext Documents at the Web

Standardized 1989 by W3C (World Wide Web Consortium)

Basic concept: "Markup" in terms of "Tags"

Drawbacks

z Restricted number of pre-defined tags

{ permanent extensions with proprietary tags

z Tags primarily describe layout aspects

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M2-5

Motivation for XML

3/5

From HTML to XML

<h1>PDACatalog</h1> <h2>Nokia 8210</h2> <table border="1"> <tr> <td>Battery</td><td>900mAh</td> </tr> <tr> <td>Weight</td><td>141g</td> </tr> … </table>

HTML describes layout of content

<PDACatalog> <Producer name="Nokia"> <PDA name="8210"> <Battery>900mAh</Battery> <Weight>141g</Weight> … </PDA> </Producer> </PDACatalog> XML describes

structureand semantics of content

Tim Bray, Co-Editor of XML 1.0:

"XML will become the ASCII of the 21st century

-basic, essential, unexciting" PDA-Catalog Battery Weight PDA-Catalog M2-6 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Motivation for XML

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Features of XML

Layout Independence

z Separation of structure and semantics of the content from its layout

Platform and Vendor Independence

z Endorsed by the W3C Internationality

z Based on the UNICODE-Standard Extensibility

z Tags can be defined and named arbitrarily – meta language Structurability

z Tags can be nested arbitrarily

Semi-structured

z Content can contain fully structured parts and fully unstructured parts Self-describing

z Tags describing structure and semantics of the content are z ... for humans: relatively easy to read and edit

z ... for machines: easy to generate and parse X-Technology Infrastructure

z W3C provides a set of XML-based standards – „XML Standards Family“ Correctness Proof

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M2-7

Well-formedness

z syntactical properties, e.g.:

{ At least 1 tag per document { Exactly 1 root tag

{ Tags have to be none-overlapping { Each tag has to have

an end tag { ....

XML-Processors parse XML documents and check

z either solely well-formedness (non-validating processors)

z or also validity (validating processors)

Can be called from within an application (e.g., browser) Decompose an XML document into its parts forming a tree,

which allows to access its parts from within an application Validity

z XML document is well-formed

and corresponds to a schema

z Schema defines vocabulary and

grammar z Alternatives: DTD or XML Schema-Standard Application Document parts Errors Catalog.DTD XML Processor Parser Entity Manager PDACatalog1.XML PDA XML-Document Features Entities

Motivation for XML

5/5

Properties of XML Documents and XML Processors

M2-8 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Document Markup Languages

1/4

History

Vannevar Bush 1945 Memex

Douglas Engelbart 1962 Augment

Ted Nelson 1965 Xanadu

William Tunniclife (GCA) 1967 GenCode

Goldfarb, Mosher, Lorie (IBM) 1969 GML (Generalized Markup Language)

ANSI 1978 Standardisierung (GenCode & GML)

Charles Goldfarb

ISO 1986 SGML (Standard Generalized Markup

Language - ISO 8879)

Tim Berners-Lee (CERN) 1989 HTML (Hypertext Markup Language)

Mark Andreessen (NCSA) 1993 HTML-Forms (XMosaic)

Netscape, Microsoft 1994 HTML-Derivations

Jon Bosak, Tim Bray, 1996 XML Working Group

James Clark et al. (W3C)

10. 2. 1998 XML 1.0

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Document Markup Languages

2/4

Memex

http://www.ps.uni-sb.de/~duchier/pub/vbush/vbush-all.shtml M2-10 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

SGML

XML

Meta Level

XHTML

Language Level

(e.g. DTDs)

HTML

MathML

Instance Level

(documents)

e

i

π

+1= 0

n f (n) =

Σ

k k=1

WML

z.B.

M2

M1

M0

[www.omg.org]

Document Markup Languages

3/4

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Document Markup Languages

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XML versus ...

... SGML

z XML vs. SGML (60 pages vs. 600 pages)

z XML has 20% of SGML’s complexity, but 80% of its functionality z XML documents are conform to an ISO revision of SGML

-WebSGML (Annex to the SGML-Standard ISO8879)

... HTML

z XML is complementary to HTML (semantic and structure vs.

layout)

z XML is not backward compatible to HTML

z Simple conversion from HTML documents to XML

... XHTML

z = Extensible HTML

z W3C Recommendation Aug. 2002 (2nd edition)

z HTML 4.01 as an „XML application“, i.e. HTML was described by

means of a XML-DTD M2-12 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Application Areas of XML

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Three Main Application Areas

Data Exchange ("Portable Data")

z Using XML solely as an exchange format or z Using also a common schema

Multi-Delivery

z One and the same content can be

delivered to different end user devices

Intelligent Retrieval

z Instead of a simple keyword search on

basis of HTML documents, structure-based search on basis of XML documents

"Mozart" -Componi

st or choc olate ball?

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M2-13

[http://www.oasis-open.org/cover/xml.html#applications]

XML-DTDs for ...

Literature "Gutenberg" Travel "openTravel" News "NewsML" Marketing "adXML" Weather "OMF" Human Resources "XML-HR" Voice Applications "VoxML" Vector Graphics "SVG" Mobile Applications "WML" Geo Applications "ANZMETA" Health Care "HL7" Mathematics "MathML” Banking "MBA” eGovernment “eGovML” Electronic Commerce z CBL: Common Business

Library (Commerce One)

z BizTalk: Microsoft

z cXML: Commerce XML

z RosettaNet:Format for

Online-Orders

z ebXML: OASIS + XML/EDI

z FnXML: Financial Products

Markup Language ...

Application Areas of XML

2/4

Industrial Sectors – "Verticalisation of XML"

M2-14 XML Schemadefinition XML Schema Namespaces XML 1.0 Introduction

Application Areas of XML

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Sources of XML Data

Inter-application and mobile devices communication

data

z e.g., Web Services

Logs and Blogs

z e.g., RSS

Metadata

z e.g., Schema, WSDL, XMP

Presentation data

z e.g., XHTML

Documents

z e.g., Word

Views of other sources of data

z e.g., Relational, LDAP, CSV, Excel, etc.

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XML

z XML language concepts incl. DTD

XML Namespaces

z Support of a global identification schema

for element names and attribute names XPath (XML Path Language)

z Path expressions for navigation in

XML documents XML Schema

z XML-based language for the definition of XML schemata

XLink, XPointer

z XML-based language for the linking of (parts of) XML documents

XSL (Extensible Stylesheet Language)

z XSLT: Transformation of XML documents (declarative) z XSL-FO: Rendering of XML documents (declarative)

DOM (Document Object Model)

z API for accessing XML documents in a procedural manner

W3C Standardization Levels: (1) Note (2) Working Draft (WD) (3) Candidate Recommendation (CR) (4) Proposed Recommendation (PR) (5) Recommendation (REC)

Application Areas of XML

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XML Standardization Family (excerpt)

„It takes ten minutes to understand (base) XML, but then ten month to understand the new technologies hung around it. „

(Peter Chen)

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Outline

Introduction

XML 1.0

z XML Document z DTD z Entities

Namespaces

XML Schema

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XML Document

1/3

Running Example: PDACatalog

<?xml

<?xml version="1.0" version="1.0" encoding="UTF-8"?>> <

<PDACatalogPDACatalog>> <!

> <Producer

<Producer name="NOKIA"name="NOKIA">> <

<ProducerNoProducerNo no="h1234"no="h1234"/>/>

<PDA

<PDA name="7110"name="7110">>

<Weight>

<Weight>141g141g</Weight></Weight>

<Price

<Price contract=contract=““yes"yes">>999999</Price></Price>

<Price

<Price contract=contract=““no"no">>49994999</Price></Price>

</PDA>

<PDA

<PDA name="8210"name="8210">>

... ... </PDA> </PDA> </Producer> </Producer> </ </PDACatalogPDACatalog>> “Root Element" or “Document Element" Prologue (optional) "xml declaration" Comment Start Tag

End Tag Attribute

Attribute Value Elementname Text “Character Data" “Element Content" of <Producer> “Empty Element" Subelement PDACatalog1.XML PDACatalog1.XML “Mixed Content" M2-18

XML 1.0

Introduction XML Schemadefinition

XML Document

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Elements and Attributes

Element- and attribute names have to be valid "XML Names"

z [ letter | _ | : ] [ letter | '0..9' | '.' | '-' | '_' | ':' ]* z "letter": A-Z, a-z, and others like ä, êς

z ':' reserved for namespaces z No length restriction z Case-sensitive

Empty elements can be represented in long form or short

form

z <ProducerNo no="h1234"></ProducerNo>or

z <ProducerNo no="h1234"/>

Attribute values must be enlosed by quotation marks

z <PDA name='8210'> or

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XML Document

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Comments

Can stretch across multiple rows

z Between start tag and end tag of an element z Before or after the root element

Restrictions

z Comment within a tag not allowed z Nesting of comments not allowed z "--" within a comment not allowed

<!--A comment may comprise also <tagNames> or &entities;

--> ...

M2-20

XML 1.0

A DTD defines vocabulary and grammar for a set of XML

documents

An XML document is allowed to reference a single DTD only

("document type declaration -

DOCTYPE

")

A DTD has to be referenced

z AFTER the prologue

z but BEFORE the root element

A DTD does NOT DEFINE the root

element of a XML document

z The root element is rather defined

within the XML document itself using the

DOCTYPE

-Declaration

z Can be an arbitrary element of the DTD

DTD

1/8

Purpose and Characteristica

<?xml version="1.0"?>

<!DOCTYPE

<!DOCTYPE PDACatalogPDACatalog ...... < <PDACatalogPDACatalog>> ... ... PDACatalog1.XML PDACatalog1.XML Catalog.DTD Catalog.DTD Root Element Definition Usage

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DTD

2/8

Incorporating DTD’s into XML Documents – 3 Alternatives

1.

External DTD, i.e., a dedicated file (

*.dtd

) identified by

means of an URI ("external subset")

<!DOCTYPE PDACatalog SYSTEM "Catalog.dtd">

2.

Internal DTD, i.e., defined within the XML document

("internal subset")

<!DOCTYPE PDACatalog […]>

3.

External & internal DTD, i.e., internal complements

external

Excursus – URL vs. URI:

z An URL (Uniform Resource Locator) identifies Internet

resources on basis of their location using the Domain Name Service (DNS)

z An URI (Uniform Resource Identifier) identifies arbitrary

resources on basis of their names (z.B. ISBN#) or other properties of the resource

z Each URL is a valid URI

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DTD

3/8

Example –

Catalog.dtd

 <!ELEMENT PDACatalog (Producer*)>

<!ELEMENT Producer (ProducerNo, PDA+)>

<!ATTLIST Producer name CDATA #REQUIRED>

<!ELEMENT ProducerNo EMPTY>

<!ATTLIST ProducerNo no ID #REQUIRED>

<!ELEMENT PDA (Weight, Price+)>

<!ATTLIST PDA name CDATA #REQUIRED>

<!ELEMENT Weight (#PCDATA)>

<!ELEMENT Price (#PCDATA)>

<!ATTLIST Price contract (yes|no) "no"> Weight ProducerNo no * 1..* Price contract PDA name PDACatalog Producer name 1 1 1..*

UML Class Diagram XML DTD

XML Element XML Attribute Legend:

1 : exactly once

1..*: once or several times

* : 0 or several times : part-of

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DTD

4/8

Element Declaration

<!ELEMENT element name

(Content Model)>

Sequence

<!ELEMENT Producer (ProducerNo, PDA+)>

Alternative

<!ELEMENT Battery (LiIo | NiMh | NiCd)>

Cardinality

z Optional (0 or once)

<!ELEMENT PDA (Comment?)>

z Null or several times

<!ELEMENT PDACatalog (Producer*)>

z Once or several times

<!ELEMENT Producer (PDA+)>

z Content model can be nested by means of paranthesis

<!ELEMENT div1 (head, (p | list | note)*, div2*)>

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DTD

5/8

Element Declaration

Empty Element

z Element may contain attributes, but neither text nor subelements

<!ELEMENT ProducerNo EMPTY>

Element Content

z Element contains subelements and optional attributes but no text

<!ELEMENT PDACatalog (Producer*)>

Mixed Content

z Element contains text and optional subelements or attributes

<!ELEMENT Price (#PCDATA)>

<!ELEMENT Price (#PCDATA | Category | Discount)*>

Element with arbitrary content

z Content not exactly specified in DTD z Used elements have to be declared anyway

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DTD

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Attribute Declaration

<!ATTLIST element name

attributename1 type default

attributename2 type default

...

>

Attribute names must be unique within an element

Default specifications

z NOT NULL #REQUIRED

z Optional Value #IMPLIED

z Default Value [#FIXED] "value"

M2-26

XML 1.0

CDATA

z String

z <!ATTLIST Producer name CDATA #REQUIRED>

ID

,

IDREF(S)

z IDensures uniqueness of

attribute values within a document

z Per element 1 attribute of

typeIDallowed only

z IDREFis a reference to an attribute of typeID

z „Referential integrity“ (untyped!) is checked by XML processor z Values of ID- and IDREF(S)-attributes must be valid XML names,

i.e., starting numbers are not allowed

DTD

7/8

Attribute Declaration – 10 Types

<!ATTLIST Example

identity ID #IMPLIED

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DTD

8/8

Attribute Declaration – 10 Types

Enumeration Type

z A pre-defined set of values consisting of XML name tokens z <!ATTLIST Price contract (yes|no) "no">

ENTITY

,

ENTITIES

z Attribute value is the name of a declared non-parsed Entity z <!ATTLIST Image filename ENTITY #REQUIRED>

NMTOKEN(S)

z "XML name tokens” are an extended form of XML names z In addition, they can start with "0..9 ", ". " and "-" z <!ATTLIST journal year NMTOKEN #REQUIRED>

NOTATION

z Attribute value is the name of a declared notation – seldomly

used

<!ATTLIST image type NOTATION (gif | tiff) #REQUIRED>

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Entities

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Overview

General Entities Usage in XML documents Parameter Entities Usage in DTDs Pre-defined Replacement of XML-specific char’s Unicode Replacement of none-ASCII-char’s User-defined Replacement of document parts Internal embedded External file Parsed Non-parsed Internal External

Referenceable, named parts of

z XML documents (plain text, markup or other arbitrary formats) z or a DTD

Purpose: Character replacement – macros, modularisation

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Purpose: Representation of XML specific characters

z e.g. <> – "escaping"

5 pre-defined Entities

z & & (ampersand)

z < < (less than)

z > > (greater than)

Example

z <formular>x < y</formular>

Usage

z As element value or attribute value

Alternative:

CDATA

-Section

z Example:

<formular>x <![CDATA[<]]> y</formular>

z “Within”CDATAonly its end is recognized (']]>')

z CDATA-Sections cannot be nested

Entities

2/9

Pre-defined Entities

z ' ' (apostrophe)

z &qout; " (quotation mark)

Interpreted as plain text, NOT as markup

M2-30

XML 1.0

Purpose

z

Representation of characters, not

available at the keyboard

z

http://www.unicode.org/

Unicode classifies characters into letters,

numbers, punctuations, symbols (general,

technical, mathematical), etc.

z Unique assignment of characters

to numbers

z Supports 25 living languages (Cyrillic, Hebrew, Hiragana, ...) z All in all approx. 50.000 different characters

Usage

z As element value or attribute value z Arbitrary Unicode-characters are

referenced via their numbers (decimal or hexadecimal)

Entities

3/9

Unicode ("Character Encoding") Entities

û û and © all represent the same character

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Text or well-formed markup is associated with a name

Declaration within the DTD:

Usage

z As element value or attribute value of the XML document z In entities themselves – but cyclic references are forbidden

Entities

4/9

User-Defined Internal Entities

<!ENTITY entityName "replacementText or Markup">

&entityName;

M2-32

XML 1.0

Purpose

z Decomposition of the XML document (similar to SSI – Server

Side Include-mechanism)

z Because of the document’s size or for reuse

Declaration within the DTD

Charakteristica

z In principal well-formed, but may contain multiple root

elements

z Reference to a DTD not allowed

Usage

z Syntax analogous to internal entities

z As element values of the XML document and within entities

themeselves

z Cyclic references forbidden z NOT within attribute values

Entities

5/9

User-Defined External Parsed Entities

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Purpose

z References to files with arbitrary formats, e.g. ASCII,

not-wellformed XML, GIF, JPEG, QuickTime Movies

z NDATAdefines a "non-parsed" Entity and specifies an arbitrary

file format

z a NOTATION-declaration is necessary to identify a corresponding

application (via an URI), which is able to process files of this format

Usage

z Only as attribute value of type ENTITY

z Syntax: entity name within quotation marks (Note: NO &...;) z Processor informs the application only that there exists a

non-parsed entity at a certain location – no expansion!

(More expressive) Alternative: W3C’s XLink-Standard

Entities

6/9

User-Defined External Non-Parsed Entities

<!ENTITY entityName SYSTEM "URI" NDATA formatName> <!NOTATION formatName SYSTEM "URI">

M2-34

XML 1.0

Entities

7/9

User-Defined Entities – Example

<?XML version="1.0"?>

<!DOCTYPE PDACatalog SYSTEM ”Catalog.dtd" [

<!ENTITY linkNokia "http://www.nokia.de/8210">

<!ENTITY address "<town>Linz</town>">

<!ENTITY features SYSTEM "feat8210.XML"> <!ENTITY bildNokia SYSTEM "/pictures/8210.jpg"

NDATA jpeg>

<!NOTATION jpeg SYSTEM "image/jpeg">

…

<!ATTLIST Image filename ENTITY #REQUIRED>

]> …

<PDA name="8210">

<Picture><Image filename="bildNokia"/></Picture> <ProducerInfo>&linkNokia;</ProducerInfo>

… &features; &address; </PDA> …

D

e

c

lar

at

io

n

Usage

internal external, parsed external, non-parsed Usage as element value Usage as attribute value

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Entities

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Parameter Entities

<!ENTITY % Battery "(type, capacity)" >

<!ELEMENT PDABatt %Battery;>

<!ELEMENT camcorderBatt %Battery;>

Internal

<!ENTITY % linkNokia SYSTEM "http://nokia.de" > %linkNokia;

External

Purpose

z Modularization of DTDs

Syntactical difference to General Entities

z % blank includedfor declaration z % blank excludedfor usage

Definition of ...

z Name and content model of elements z Attribute declaration

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XML 1.0

Entities

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Parameter Entities – Overriding

<!ENTITY % residental_content "address,rooms">

External DTD

Internal DTD of a XML document

<!ENTITY % residental_content "address,rooms,baths">

A Parameter Entity defined within an external DTD can be

arbitrarily overriden within the internal DTD of a XML

document

This allows to adapt the external DTD to the requirements

of single XML documents without having to change the

external DTD

Thus, the Parameter Entity is used as a kind of

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Outline

Introduction

XML 1.0

Namespaces

XML Schema

M2-38

Namespaces

XML 1.0

Namespaces

1/5

A XML namespace (NS) allows a unique global

identification of elments and attributes

z W3C-REC "Namespaces in XML", 14th Jan. 1999 (13 pages)

For this, elements and attributes of a domain (e.g.

MathML) are assigned to one or more NS

z XSL uses, e.g., different namespaces for XSLT and XSL-FO

A NS is represented by an URI

z Needs not directly refer to the corresponding vocabulary

z Thus, provides a level of indirection which allows to decouple the

location of the vocabulary from the unique identifier – the URI

The associated elements and attributes have to be qualified

by means of this URI in case of usage, thus being made

globaly unique

z This allows the reuse and especially the combination

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Namespaces

2/5

NS with Prefix vs. Default NS

BUT: URIs cannot be used for direct qualification

z This is since URIs normally contain characters which are not allowed as

part of valid XML names (e.g., " / ", " & ")

z Instead, user-defined prefixes have to be used

One ore more NS are declared on basis of the pre-defined

attributexmlns

z This attribute can be defined in the context of any element of the DTD

z The name of the element itself where the NS has been declared as well

as direct and indirect subelements and attributes can be qualified with the NS – „NS-inheritance“

Default NS

z Also declared via the pre-defined attributexmlns– BUT – only 1 per

element, and without declaring any prefix

z None-qualified subelements are automatically associated with the

default NS, attributes NOT

z Can be overriden within subelements

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Namespaces

XML 1.0

Namespaces

3/5

Declaration and Usage

... <edi:HC

xmlns:edi='http://ecommerce.org/schema'

xmlns='http://www.mobildev.com/schema'> <model name="8210">

<edi:price edi:units='Euro'>32.18</edi:price> <price währung='USD'>25.16</price>

...

</model>... </edi:HC>

NS Prefix (optional) _{URI of the NS} Pre-defined Attribute

for NS Declaration

Default-NS (no Prefix)

The NS of the element edi:priceis http://ecommerce.org/schema The NS of the elementsmodeland priceis the default NS

http://www.mobildev.com/schema

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Namespaces

4/5

... and DTDs

NS are in principle independent of DTDs

z Can be used in documents with or without DTDs

BUT:

z All elements and attributes which are qualified in the XML

document must also be declared appropriately within the DTD

z Huge Overhead – this is since DTD’s are not aware of NS z <edi:HC> ... <!ELEMENT edi:HC (....)>

z <edi:price> ... <!ELEMENT edi:price (#PCDATA)>

What can be done is to specify a default NS within the DTD

z <!ATTLIST edi:HC xmlns

CDATA #FIXED 'http://www.mobildev.com/schema'>

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Namespaces

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Exemplary NS-URIs

RDF http://www.w3.org/1999/02/22-rdf-syntax-ns# http://www.w3.org/2000/01/rdf-schema# MathMLhttp://www.w3.org/1998/Math/MathML XHTML http://www.w3.org/1999/xhtml SMIL http://www.w3.org/TR/REC-smil XSL http://www.w3.org/1999/XSL/Transform http://www.w3.org/1999/XSL/Format

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M2-43

Outline

Introduction

XML 1.0

Namespaces

XML Schema

z Introduction

z Elements and Attributes z Pre-defined Datatypes z User-defined Datatypes

z Keys

z Schema Composition z Schema Modeling Styles

z Comparison DTD – XML Schema

M2-44

XML Schema Namespaces XML 1.0 Introduction XML Schemadefinition

Introduction

DTD versus XML Schema 1/2

Drawbacks DTDs

z Proprietary syntax

z Few datatypes, in fact only

one – String

z Global definition of elements z Parameter Entities for

modularization & overriding

z ID, IDREF(S): Severe restrictions

Advantages XML Schema

z XML as syntax z Numerous pre-defined datatypes

z User-defined simple and

complex datatypes

z Inheritance z Keys, references:

flexible concept

XML Schema

z Definition of the structure of XML documents z W3C REC May 2001, approx. 420 pages z W3C REC 2nd edition October 2004

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M2-45

<simpleType name="producerNoType"> ...

<element name="ProducerNo"

type="hc:producerNoType" minOccurs="1" maxOccurs="1"/> <element name=„PDA" minOccurs="1" maxOccurs="unbounded">

<element name="Weight" type="string" minOccurs="1" maxOccurs="1"/> <element name="Battery" type="string" minOccurs="1" maxOccurs="1"/> </sequence> ... </schema> Catalog.xsd Catalog.dtd

Introduction

DTD versus XML Schema 2/2

...

<!ELEMENT PDACatalog (Producer*) > <!ELEMENT Producer (ProducerNo, PDA+)> <!ELEMENT PDA (Weight, Battery)> <!ELEMENT Weight (#PCDATA)> <!ELEMENT Battery (#PCDATA)> ...

M2-46

XML Schema

Namespaces XML 1.0

Namespace for own Vocabulary

z Namespace (NS) of the vocabulary to be defined can be declared

by means of attribute targetNamespace(optional!)

NS of the XML Schema-Standard Vocabulary

z Declaration is obligatory!

z Additional NS (i.e., vocabularies) can be incorporated

A single NS can be defined as Default–NS

z Either own NS, XML Schema–NS or other NS z For all other NS used, a prefix is obligatory

<?xml version="1.0"?>

<schema targetNamespace="http://www.ifs.uni-linz.ac.at/hc"

xmlns:hc="http://www.ifs.uni-linz.ac.at/hc" xmlns="http://www.w3.org/2001/XMLSchema" attributeFormDefault="qualified" elementFormDefault="qualified"> ...

Introduction

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M2-47

Schema of a XML document is defined within the root

element via the attribute

schemaLocation

z 1. Part: targetNamespaceof the schema

z 2. Part: location of the schema document

Catalog.xsd Catalog1.xml <?xml version="1.0"?> <schema targetNamespace="http://www.ifs.uni-linz.ac.at/hc" xmlns:hc="http://www.ifs.uni-linz.ac.at/hc" xmlns="http://www.w3.org/2001/XMLSchema" attributeFormDefault="qualified" elementFormDefault="qualified"> ... <?xml version="1.0"?>

<PDACatalog xsi:schemaLocation="http://www.ifs.uni-linz.ac.at/hcCatalog.xsd"

xmlns="http://www.ifs.uni-linz.ac.at/hc"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance“ >

...

Introduction

Usage of NS in the XML Document

xsi:noNamespaceSchemaLocation= "directPathToXSD_File"

M2-48

Element

Attribut

Global Definition

z Direct subelement of schema

z NOTE: the root element of the XML document is required to

be defined as global element!

Local Definition

z Definition on an arbitrary nesting level

Analoguosly for Datatypes!

<elementname="name"type="type"minOccurs="int"maxOccurs="int|unbounded"... /> Simple or

Complex Type

Cardinality: Upper/Lower Bounds (only in “local” elements)

<attributename="name"type="type"use="how-its-used"default/fixed="value"... />

Values: required, optional, prohibited (only in “local” attributes)

only relevant, if “use” is not defined Simple Type

Elements and Attributes 1/3

Global / Local Definition

(25)

M2-49

Global or Local Datatypes

Reference to an existing Element or Attribute

<elementname="name"minOccurs="int"maxOccurs="int|unbounded"...> <complexType>…</complexType>

</element>

<elementref="name"minOccurs="int"maxOccurs="int|unbounded".../> <attributename="name"use="how-its-used"default/fixed="value"...>

<attributeref="name"use="how-its-used"default/fixed="value".../>

Elements and Attributes 2/3

Global / Local Datatypes and References

M2-50

XML Schema Namespaces XML 1.0 Introduction XML Schemadefinition <schema ...> <element name="Producer"> <complexType> <sequence>

<element name="ProducerNo" type="hc:producerNoType" minOccurs="1" maxOccurs="1"/>

<element ref="hc:PDA" maxOccurs="unbounded"/> </sequence>

<attributename="name" type="string" use="required"/> </complexType>

</element>

<element name="PDA"> <complexType>

<element name="Weight" type="string"/> <element name="Battery" type="string"/> </sequence> </complexType> </element> <simpleType name="producerNo"> … Global Element, local Datatype Reference to a global Element Local Element, global Datatype Global Element, local Datatype Local Element, pre-def. Datatype Local Attribute, pre-def. Datatype

Elements and Attributes 3/3

Summarizing Example – Global/Local

(26)

M2-51

string boolean float double duration date Time

time date gYear gMonth Day gDay gYear Month anyType anySimple Type (all complex types)

gMonth hex Binary base64 Binary any URI QName NOTATION normalized String token

language NMTOKEN Name

NMTOKENS NCName ID IDREF ENTITY IDREFS ENTITIES decimal integer nonPositiveInteger nonNegativeInteger

negativeInteger positiveInteger unsignedLong

unsignedInt unsignedShort unsignedByte long int short byte (W3C REC, 28th Oct. 2004) z Primitive (atomic) z Derived

Pre-Defined Datatypes

1/4 M2-52

XML Schema

Namespaces XML 1.0

Because of backward-compatibility reasons, usable only as types for attributes

Pre-Defined Datatypes

2/4

String Datatypes

string anySimpleType hex Binary base64 Binary any

URI NOTATION QName

normalized String token language NMTOKEN Name NMTOKENS NCName ID IDREF ENTITY IDREFS ENTITIES

z Pre-defined primitive Types

z Pre-defined derived Types

Backward-compatibility to DTDs Normalized String with whitespace replacement. Each Tab, Linefeed and CR is replaced by Blank.

"Tokenized" String – all whitespace characters are replaced by blanks,

all starting and ending blanks are deleted and multiple consecutive blanks are replaced by a single one.

Standardized language codes (e.g. en, en-US, de, de-DE) Name token: String without blanks (z.B. "CMS", "234234")

XML-Name: must start with letter, ":" or "-" (e.g., "CMS", "-1") Name without prefix

String-Datatype without Whitespace-Replacement

Binary string-encoded Datatypes

Qualified name: supports the usage of names with NS-prefix

(27)

M2-53

Pre-defined Datatypes

3/4

Numerical Datatypes

float double anySimpleType decimal integer nonPositiveInteger nonNegativeInteger

negativeInteger positiveInteger unsignedLong

unsignedInt unsignedShort unsignedByte long int short byte

z Pre-defined primitive Types

z Pre-defined derived Types

Decimal Numbers: decimal separator ".", "+" or "-" possible.

64, 32, 16 or 8 Bit

Floating Point Numbers: simple (32 Bits) and double (64 Bits) precision

boolean

M2-54

XML Schema

Namespaces XML 1.0

Pre-defined Datatypes

4/4

Date- and Time Datatypes

durationtime dateTime dategYearMonthgYear gMonthDay gDay anySimpleType gMonth "CCYY-MM-DDThh:mm:ss" "CCYY-MM-DD" "CCYY-MM" "CCYY" "--MM-DD" "---DD" "--MM" "hh:mm:ss" "PnYnMnDTnHnMnS"

Day of the month

Day of the year

(28)

M2-55

User-defined Datatypes

Alternatives

Should the Type contain Elements or Attributes? Unstructured Content <simpleType> Structured Content <complexType> Derivation <restriction> <union> or <list> Derivation <restriction> <extension> Nesting <sequence> <all> <choice> Empty / Mixed Name d / An onymo u s

Should the Type contain Elements?

yes no

Attributes & Elements

<complexContent> Attributes <simpleContent> Note: <complexContent> only necessary in case of derivation from a user-defined type M2-56

User-defined Datatypes

Alternatives – Examples

<xsd:complexType name="BookTypeWithID"> <xsd:complexContent> <xsd:extension base="BookType">

<xsd:attribute name="ID" type="xsd:token"/>

</xsd:extension> </xsd:complexContent> </xsd:complexType> <xsd:complexType> <xsd:sequence> .... </xsd:sequence> </xsd:complexType> <xsd:simpleType name="longitudeType"> <xsd:restriction base="xsd:integer"> <xsd:minInclusive value="-180"/> <xsd:maxInclusive value="180"/> </xsd:restriction> </xsd:simpleType> <xsd:integer> No Derivation Derivation Simple Complex User-defined Pre-defined Anonymous Named

(29)

M2-57

Restriction of a pre-defined datatype

z <restriction>

Union of pre-defined datatypes (Extension)

z <union>

z Values must correspond to at least one of the combined

datatypes

List of values of one pre-defined datatype

(or again of a List-Datatype)

z <list>

User-defined Datatypes

Derived Simple Datatypes –

<

simpleType

>

M2-58

XML Schema

Namespaces XML 1.0

Alternative Definition Possibilities

z Referencing an existing datatype via the attribute base

z Local definition from scratch by using simpleTypeas subelement of the

restriction-Element

12 Possible Restrictions, depending on the base datatype z length z minLength z maxLength z pattern z enumeration z minInclusive z maxInclusive z minExclusive z maxExclusive z whiteSpace z totalDigits z fractionDigits

<simpleTypename="batteryType"> <restrictionbase="string">

</simpleType>

<Battery>NiCd</Battery> XML-Document

User-defined Datatypes

(30)

M2-59

User-defined Datatypes

Derived Simple Datatypes

<

simpleType

>

–

restriction

M2-60

XML Schema

Namespaces XML 1.0

User-defined Datatypes

Derived Simple Datatypes

<

simpleType

>

–

restriction

Restrictions using a “pattern” element

Restrictions of the lexical values

Simple regular expressions

z Normal characters: "C&A"

z Categories of characters:"\p{IsBasicLatin}"

z Sets of characters: "[\p{IsBasicLatin}-[\d]]" z Quantifiers: "[a-zA-Z]{1,8}"

z Paranthesis: "(XML(\s+|-))?Schema" z Combinations of these expressions

(31)

M2-61

Alternative Definition Possibilities

z Referencing an existing datatype via attributes

(memberTypesor itemType)

z Local definition from scratch by using simpleTypeas subelement

of the union- or list-Elements <simpleType name="PDAFeatureType">

<unionmemberTypes="hc:PDAColor hc:PDARobustness"/> </simpleType>

<element name="PDAFeatureList" type="hc:PDAFeatureListType"/> XML-Dokument:

<PDAFeatureList>blue waterproof shockproof</PDAFeatureList>

User-defined Datatype

Derived Simple Datatypes

<

simpleType

>

–

union/list

M2-62

XML Schema

Namespaces XML 1.0

Nested Elements

z Possible within a complex datatype only

Attributes

z Possible within a complex datatype only z Independentof the existence of nested elements

Empty Content

z Possible within a complex datatype only z Does not have nested elements

Mixed Content

z Datatype may contain nested elements and text

z In contrast to DTDs, for nested elements, the ordering and

cardinality properties can be arbitrarily specified

User-defined Datatypes

(32)

M2-63

Sequence –

<sequence>

Choice –

<choice>

Arbitrary Ordering –

<all>

z Nested Elements can be used in arbitrary order

Cardinality

z Expressed by means of minOccursand maxOccurs <complexTypename=“PDAType">

<sequenceminOccurs="1" maxOccurs="1">

User-defined Datatype

<

complexType

>

– Nested Elements / Attributes

M2-64

XML Schema

Namespaces XML 1.0

</complexType>

<PDA>Type Nokia 7110 has <Weight>141g</Weight>and <Battery>900mAh</Battery>

</PDA>

XML Document

User-defined Datatypes

(33)

M2-65

Extension

z <extension>

z Additional nested elements and/or attributes

Restriction

z <restriction>

z Domain z Cardinality

Abstract Datatypes

z <complexType>with attribute abstract = "true“

Prohibition of Derivation

z <complexType>with attribute final

z Potential values: #all, restriction, extension

User-defined Datatypes

<

complexType

>

– Derivation of Complex Types

M2-66

XML Schema

Namespaces XML 1.0

Elements are attached at the end

Extension must be specified within a

<

complexContent

>

-Tag

<extensionbase="hc:PDAType" > <sequence>

<element name=“Band" type="string" minOccurs="1" maxOccurs="1"/> <element name="Feature" type="string"

minOccurs="1" maxOccurs="10"/> </sequence> </extension> </complexContent> </complexType> extendedPDAType PDAType

User-defined Datatypes

(34)

M2-67

The declarations of the base datatype

which should retain must be repeated

Restriction must be specified within a

<

complexContent

>

-Tag

<restrictionbase="hc:extendedPDAType"> <sequence>

</restriction> </complexContent> </complexType>

User-defined Datatypes

<

complexType

>

– Derivation via Restriction

extendedPDAType

restrictedPDAType PDAType

M2-68

Static

Dynamic

z Definition of the derived datatype within the XML document via

the attribute typeof the XML Schema Instance (xsi) NS

Element PDA has datatype PDAType <PDA> <Weight>141g</Weight> <Battery>900mAh</Battery> </PDA> <PDA xsi:type=“extendedPDAType"> <Weight>115g</Weight> <Battery>550mAh</Battery> <Band>Dualband</Band> <Feature>Waterproof</Feature> </PDA> Datatype extendedPDAType is derived from PDAType: Extension with

Band & Feature

User-defined Datatype

(35)

M2-69

Characteristics of a key (

key

)

z Value (combination) must be unique z Value must exist

z Key must be defined as subelement of another element –

following the type definition

Candidates for keys (

field

)

z Elements with simple datatypes only! z Attributes

z Combinations of elements and attributes

Scope can be defined (

selector

)

Reference to key can be defined (

keyref

)

Elements, Attributes and Combinations thereof can be

defined to be unique (

unique

)

z Value (combination) must be unique z Value need NOT exist

Keys

1/2

M2-70

Keys

2/2 <element name="PDACatalog"> <complexType> ...</complexType> <keyname=“typeKey"> <selectorxpath="hc:Producer/hc:PDA"/> <fieldxpath="@name"/> <fieldxpath="@version"/> </key>

<keyrefname="refToTypeKey" refer="hc:typeKey"> <selectorxpath="hc:Stock/hc:PDAQuantity"/> <fieldxpath="@name"/>

<fieldxpath="@version"/> </keyref>

</element>

PDA Name Version Weight ... PDAQuantity Name Version Quantity <element name="PDACatalog"> <complexType> ...</complexType> <uniquename="uniqueProducerNo"> <selector xpath="hc:Producer"/> <field xpath="@producerNo"/> </unique> </element>

(36)

M2-71

Group of Elements

<groupname="mainData">

</group>

<groupref="hc:mainData"/>

</complexType>

Schema Composition

Within a Schema

1/2

M2-72

Group of Attributes

<attributeGroupname="BatteryAttributeGroup"> <attribute name="type" type="string" default="NiMh"/> <attribute name=“capacity" type="string" use="required"/> </attributeGroup> <complexType name=“BatteryType"> <sequence>...</sequence> <attributeGroupref="hc:BatteryAttributeGroup"/> </complexType>

Schema Composition

Within a Schema

2/2

(37)

M2-73

Incorporation of other schemata via

include

,

redefine

and

import

z include, redefineand import elements must be subelements

of schemaprior to any other declaration

Include of a Schema –

include

z NS of included schema must be equal to the NS of the including

schema or no NS at all

z The included schema can be used as if it were declared directly

within the including schema

<schema...>

<includeschemaLocation="PDA.xsd"/>...

Schema Composition

Different Schemata 1/2

M2-74

XML Schema

Namespaces XML 1.0

Including and Redefining a Schema –

redefine

z Same functionality as include

z In addition, included components (simpleType, complexType, group, attributeGroup)can be newly defined

z New definitions replace the original ones

Import of a Schema –

import

z Imported schema can have an arbitrary NS (could be unequal to

the current one)or none

<importnamespace="http://" http://www.somewhere.else.com" schemaLocation="Producer.xsd"/>... <redefineschemaLocation="PDA.xsd"> <complexType name=“PDAType">....</complexType>... </redefine>...

Schema Composition

Different Schemata 2/2

(38)

M2-75

Schema Modeling Styles

Non-Normative Datamodel of XML Schema Concepts

Legend:

http://www.w3.org/TR/xmlschema-1/

M2-76

XML Schema

Namespaces XML 1.0

Schema Modeling Styles

XML Schema Concepts in Practice

Analysis of 1400

Schemata of diverse standard vocabularies

z Open Travel Alliance

(OTA), z Human Resource XML (HR-XML), z W3C, z Global Justice XML, z etc.

P. Kiel, Profiling XML Schema,

(39)

M2-77

Schema Modeling Styles

Relationships /Global vs. Local /Element vs. Type

Relationships

z Realisation by means of nesting or via references

Global Elements/Attribute-Declarations

z Pre-requisite for reuse in the same/another schema

z Root element must be global

Local Element/Attribute-Declarations

z In case that a declaration makes sense only in combination with the

declared type

Local Element Declarations

z Can occur with different structure but the same name in different types

Local Attribute Declarations

z Makes sense since attributes are most often tightly coupled to elements

Three Stereotypical Design Forms

z Russian Doll Design

z Salami Slice Design

z Venetian Blinds Design

Literature

z XMLSchema Best Practices (Roger Costello): www.xfront.com

z P. Kiel, Profiling XML Schema, http://www.xml.com/pub/a/2006/09/20/profiling-xml-schema.html

M2-78

Nested Element

Declarations

z Local declarations only z Prevents global types

Advantages

z Structure obvious (corresponds to the XML document‘s structure) z Prevents side-effects

Disadvantages

z Danger of deep nesting levels

z No reuse of declarations – redundancies z No extensibility in terms of derivation

Schema Modeling Styles

Russian Doll Design

(40)

M2-79

Global Element Declarations

z Usage of global elements per

reference (ref-Attribute)

z Each global element can be a

root element

Advantages

z Reuse of elements

Disadvantages

z Large numger of global elements

{ Confusing

{ Danger of side-effects in case of

changes to global elements

z No extensibility in terms of derivation

Schema Modeling Styles

Salami Slice Design

M2-80

XML Schema

Namespaces XML 1.0

Global Type Declarations

z Elements, except the root

element, are declared locally

Advantages

z Reuse of types

{ A named type is available for

each element and attribute

{ Types can be imported from

other schemata

z Extensibility by derivation

Disadvantages

z Large number of global types

{ Confusing