pal gov.tutorial2.session3.xml schemas

1PalGov © 2011 1PalGov © 2011

أكاديمية الحكومة اإللكترونية الفلسطينيةThe Palestinian eGovernment Academy

www.egovacademy.ps

Dr. Ismail M. Romi

Palestine Polytechnic University

Tutorial II: Data Integration and Open Information Systems

Session3

XML Schemas


About

This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the

Commission of the European Communities, grant agreement 511159-TEMPUS-1-

2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps

University of Trento, Italy

University of Namur, Belgium

Vrije Universiteit Brussel, Belgium

TrueTrust, UK

Birzeit University, Palestine

(Coordinator )

Palestine Polytechnic University, Palestine

Palestine Technical University, PalestineUniversité de Savoie, France

Ministry of Local Government, Palestine

Ministry of Telecom and IT, Palestine

Ministry of Interior, Palestine

Project Consortium:

Coordinator:

Dr. Mustafa Jarrar

Birzeit University, P.O.Box 14- Birzeit, Palestine

Telfax:+972 2 2982935 [email protected]

http://www.egovacademy.ps/


© Copyright Notes

Everyone is encouraged to use this material, or part of it, but should

properly cite the project (logo and website), and the author of that part.

No part of this tutorial may be reproduced or modified in any form or by

any means, without prior written permission from the project, who have

the full copyrights on the material.

Attribution-NonCommercial-ShareAlike

CC-BY-NC-SA

This license lets others remix, tweak, and build upon your work non-

commercially, as long as they credit you and license their new creations

under the identical terms.

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Tutorial Map

Topic h

Session 1: XML Basics and Namespaces 3

Session 2: XML DTD’s 3

Session 3: XML Schemas 3

Session 4: Lab-XML Schemas 3

Session 5: RDF and RDFs 3

Session 6: Lab-RDF and RDFs 3

Session 7: OWL (Ontology Web Language) 3

Session 8: Lab-OWL 3

Session 9: Lab-RDF Stores -Challenges and Solutions 3

Session 10: Lab-SPARQL 3

Session 11: Lab-Oracle Semantic Technology 3

Session 12_1: The problem of Data Integration 1.5

Session 12_2: Architectural Solutions for the Integration Issues 1.5

Session 13_1: Data Schema Integration 1

Session 13_2: GAV and LAV Integration 1

Session 13_3: Data Integration and Fusion using RDF 1

Session 14: Lab-Data Integration and Fusion using RDF 3

Session 15_1: Data Web and Linked Data 1.5

Session 15_2: RDFa 1.5

Session 16: Lab-RDFa 3

Intended Learning Objectives

A: Knowledge and Understanding

2a1: Describe tree and graph data models.

2a2: Understand the notation of XML, RDF, RDFS, and OWL.

2a3: Demonstrate knowledge about querying techniques for data

models as SPARQL and XPath.

2a4: Explain the concepts of identity management and Linked data.

2a5: Demonstrate knowledge about Integration &fusion of

heterogeneous data.

B: Intellectual Skills

2b1: Represent data using tree and graph data models (XML &

RDF).

2b2: Describe data semantics using RDFS and OWL.

2b3: Manage and query data represented in RDF, XML, OWL.

2b4: Integrate and fuse heterogeneous data.

C: Professional and Practical Skills

2c1: Using Oracle Semantic Technology and/or Virtuoso to store

and query RDF stores.

D: General and Transferable Skills2d1: Working with team.

2d2: Presenting and defending ideas.

2d3: Use of creativity and innovation in problem solving.

2d4: Develop communication skills and logical reasoning abilities.


Session ILO’s:

After completing this session students will be able to:

•Manage data represented in XML.

•Represent data using tree and graph data models.

•Build Well-Formed XML Document.


Session4: XML Schemas

Session Overview:

<Benefits of XML Schemas />

<How to create and use XML Schemas/>

<How to document your XML Schemas/>


XML Schema

• The term XML Schema is used to refer to the specific

W3C XML Schema technology.

• W3C XML Schemas, much like DTDs, enable you to

describe the structure of an XML document.

• XML Schema definitions are also commonly referred

to as XSDs.


Benefits of XML Schemas

XML Schemas are created using basic XML, while DTDs

utilize a separate syntax.

XML Schemas fully support the Namespace

Recommendation.

XML Schemas enable you to validate text element content

based on built-in and user-defined data types.

XML Schemas enable you to more easily create complex

and reusable content models.

XML Schemas enable the modeling of programming

concepts such as object inheritance and type substitution.


Do We Still Need DTDs?

• XML Schemas provide better features for describing

documents—as well as a more common syntax—they

provide no ENTITY functionality.

• In many XML documents and applications, the ENTITY

declaration is important.

• DTD can be embedded in the xml document.

• DTD supported by the SGML.

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XML Schemas

XML Schema divided into three parts:

An introduction to XML Schema concepts at:

www.w3.org/TR/xmlschema-0/

A document that defines all of the structures used in XML

Schemas at: ww.w3.org/TR/xmlschema-1/

A document that describes XML Schema data types at

www.w3.org/TR/xmlschema-2/

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The XML Schema Document

• Most XML Schemas are stored within a separate XML

document.

• XML Schemas function very similarly to external DTDs

• XML document contains a reference to the XML Schema

that defines its vocabulary.

• An XML document that adheres to a particular XML

Schema vocabulary is called an XML Schema instance document.

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XSD Example

<?xml version=‖1.0‖?>

<schema xmlns=‖http://www.w3.org/2001/XMLSchema‖

xmlns:target=‖http://www.example.com/name‖

targetNamespace=‖http://www.example.com/name‖

elementFormDefault=‖qualified‖>

<element name=‖name‖>

<complexType>

<sequence>

<element name=‖first‖ type=‖string‖/>

<element name=‖middle‖ type=‖string‖/>

<element name=‖last‖ type=‖string‖/>

</sequence>

<attribute name=‖title‖ type=‖string‖/>

</complexType>

</element>

</schema>

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The <schema> Element

The <schema> element is the root element of every XML

Schema:

<?xml version="1.0"?>

<xs:schema>

...

...

</xs:schema>

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The <schema> Element….Cont

The <schema> element may contain some attributes.

A schema declaration often looks something like this:

<?xml version="1.0"?>

<xs:schema

xmlns:xs= “http://www.w3.org/2001/XMLSchema”

targetNamespace= “http://www.w3schools.com”

xmlns= “http://www.w3schools.com”

elementFormDefault= "qualified">

...

...

</xs:schema>

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The XML schema Namespace

• You can use any of the following <schema>:<schema

xmlns=”http://www.w3.org/2001/XMLSchema”>

<xs:schema

xmlns:xs=”http://www.w3.org/2001/XMLSchema”>

<xsd:schema

xmlns:xsd=”http://www.w3.org/2001/XMLSchema”>

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• Indicates that the elements and data types

used in the schema come from the

―http://www.w3.org/2001/XMLSchema" namespace.

• It also specifies that the elements and data

types that come from the

―http://www.w3.org/2001/XMLSchema" namespace

should be prefixed with xs: or xsd:

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Target Namespaces

• The primary purpose of XML Schemas is to declare

vocabularies.

• These vocabularies can be identified by a namespace that

is specified in the target namespace attribute.

• When declaring a target namespace, it is important to

include a matching namespace declaration.

<xs:schema xmlns:xs=‖http://www.w3.org/2001/XMLSchema‖


xmlns=‖http://www.example.com/name‖>

Indicates that the

elements defined by this

schema come from this

target namespace.

Indicates the

default namespace.

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Element and Attribute Qualification

<schema xmlns=‖http://www.w3.org/2001/XMLSchema‖

xmlns:target=‖http://www.example.com/name‖


elementFormDefault=‖qualified‖>

elementFromDefault = ―qualified‖ or ―unqualified‖

attributeFromDefault ― qualified‖ or ―unqualified‖

• qualified: if it has an associated namespace.

• unqualified: if it hasn’t associated namespaces

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Simple <element> Declarations

<xs:element name="xxx" type="yyy"/>

xxx: the name of the element • The name must follow the rules for XML names.

yyy: the data type of the element.

XML Schema has a lot of built-in data types.

The most common types are:– xs:string

– xs:decimal

– xs:integer

– xs:boolean

– xs:date

– xs:time

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Example

• Here are some simple XML elements:

<lastname>Jones</lastname>

<age>36</age>

<dateborn>1970-03-27</dateborn>

• Here are the corresponding simple element

definitions:

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

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

<xs:element name="dateborn" type="xs:date"/>

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Cardinality

• Cardinality represents the number of

occurrences of a specific element within a

content model.

<element name=‖first‖ type=‖string‖ minOccurs=‖x‖ maxOccurs=‖y‖/>

• x : minimum number of occurrence, default =1

• y : maximum number of occurrence, unbound: open occurrence

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Default and Fixed Values

Simple elements may have a default value OR a fixed value specified.

Default value is automatically assigned to the element when no other value is specified.

In the following example the default value is "red":

<xs:element name="color" type="xs:string" default="red"/>

Fixed value is also automatically assigned to the element, and you cannot specify another value. In the following example the fixed value is "red":

<xs:element name="color" type="xs:string" fixed="red"/>

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<complexType> Declarations

A complex element is an XML element that contains other elements and/or attributes.

There are four kinds of complex elements:

empty elements

elements that contain only other elements

elements that contain only text

elements that contain both other elements and text

Note: Each of these elements may contain attributes as well!

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empty elements

• A complex XML element, "product", which is

empty:

<product pid="1345"/>

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elements that contain only other elements

• A complex XML element, "employee", which

contains only other elements:

<employee>

<firstname>John</firstname>

<lastname>Smith</lastname>

</employee>

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elements that contain only text

• A complex XML element, "food", which

contains only text:

<food type="dessert“ Ice cream</food>

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elements that contain both other elements and text

• A complex XML element, "description",

which contains both elements and text:

<description> It happened on

<date lang="norwegian">03.03.99</date> ....

</description>

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How to Define a Complex Element

• Look at this complex XML element,

"employee", which contains only other

elements:

<employee>

<firstname>John</firstname>

<lastname>Smith</lastname>

</employee>

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The "employee" element can be declared directly by naming the element, like this:

<xs:element name="employee">

<xs:complexType>

<xs:sequence>

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

<xs:element name="lastname“ type="xs:string"/>

</xs:sequence>

</xs:complexType>

</xs:element>

• If you use the method described above, only the "employee" element can use the specified complex type.

• Note that the child elements, "firstname" and "lastname", are surrounded by the <sequence> indicator. This means that the child elements must appear in the same order as they are declared.

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<attribute> Declarations

• The syntax for defining an attribute is:

<xs:attribute name="xxx" type="yyy"/>

– Where xxx is the name of the attribute and yyy specifies

the data type of the attribute.

– Simple elements can’t have attributes

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Summary

• XML Schema is used to refer to the specific W3C

XML Schema technology.

• W3C XML Schemas, much like DTDs, enable you

to describe the structure of an XML document.

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Refrences

• Hunter, H, Rafter, J., Fawcett, J., Vlist, E., Ayers, D., Duckett, J., Watt,

A., McKinnon,L., (2007), "Beginning XML", 4th Ed.,Wiley Publishing Inc: Indiana, USA.

• Ray, E., (2003), "Learning XML", 2nd Ed., O’Rreilly Media Inc.: USA.

• Amiano, M., D'Cruz, C., Ethier, K., Thomas, M., (2006), XML:

Problem - Design – Solution", Wiley Publishing Inc: Indiana, USA.

• http://www.w3.org

• http://www.w3schools.com

• http://www.xml.com

• http://www.xml.org

http://www.w3.org/

http://www.w3.org/

http://www.w3.org/

http://www.w3schools.com/



http://www.xml.com/

http://www.xml.org/