Pal gov.tutorial3.session2.xml ns and schema

‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps

Tutorial III:
Process Integration and Service Oriented Architectures

Session 2
Overview XML NS and Schema

Prepared By

Mohammed Aldasht

Reviewed by
Prof. Marco Ronchetti and Prof. Paolo Bouquet, Trento University, Italy
PalGov © 2011 1

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
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )

Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium

Palestine Technical University, Palestine
Université de Savoie, France

Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine

Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

© 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.

PalGov © 2011 3

Tutorial Map

Intended Learning Objectives
A: Knowledge and Understanding
Title T Name
3a1: Demonstrate knowledge of the fundamentals of middleware.
3a2: Describe the concept behind web service protocols.
Session0: Syllabus and overview 0 Aldasht
3a3: Explain the concept of service oriented architecture. Sesson1: Introduction to SOA 2 Aldasht
3a4: Explain the concept of enterprise service bus. Session2: XML namespaces & XML schema 2 Aldasht
3a5: Understanding WSDL service interfaces in UDDI. Session 3: Xpath & Xquery 4 Romi
B: Intellectual Skills Session4: REST web services 3 M. Melhem
3b1: Design, develop, and deploy applications based on Service Session5: Lab2: Practice on REST 3 M. Melhem
Oriented Architecture (SOA). Session 6: SOAP 2 Aldasht
3b2: use Business Process Execution Language (BPEL). Session 7: WSDL 3 Aldasht
3b3: using WSDL to describe web services.
Session8: Lab 3: WSDL practice 3 Aldasht
C: Professional and Practical Skills Session9: ESB 4 Aldasht
3c1: setup, Invoke, and deploy web services using integrated
Session10: Lab4: Practice on ESB 4 Aldasht
development environment.
Session11: integration patterns 4 M. Melhem
3c2: construct and use REST and SOAP messages for web
services communication. Session12: Lab5: integration patterns 4 M. Melhem
D: General and Transferable Skills Session13: BPEL 3 Aldasht
d1: Working with team. Session14: Lab6: Practice on BPEL 3 Aldasht
d2: Presenting and defending ideas. Session15: UDDI 2 Aldasht
d3: Use of creativity and innovation in problem solving.
d4: Develop communication skills and logical reasoning abilities.

Session Outlines

 XML Overview
 XML document and Grammars
 XML information set
 XML Namespaces
 XML Schema

e-Government Lifelong Learning 5

Overview

• XML is a markup language, like HTML, consists of markup
and text.
• Markup is composed of individual tags.
• Both HTML and XML are languages for exchanging data, but
there is a difference between them.
• See next slide for and initial XML example.


Valid and well-formed XML document

• Valid XML document is one that comply with the constraints
expressed through a given grammar.
• A well-formed XML document is one that comply with XML
syntax expressed in the XML standard.
– But not associated with a distinct grammar.


XML grammars

• Specified by two dominant concepts:
– XML schema and Document Type Definitions (DTDs)
• XML schema is powerful to express structural XML document
constraints than DTDs.
• XML document complying with a DTD or a schema is called
and XML instance or instance document.
• See next slide, for the relationship between XML document
grammar and XML instances resulting from applying the
grammar.


XML document grammar and valid XML instances, [2]

XML Instance,
XML Schema, DTD XML Instance,
Instance Document
(XML Document Grammar) XML Instance,
Instance Document
XML Instance,
Instance Document
Valid Instance Document
Documents


XML processor

• Applications are interested in the
structural information and the
XML instance, when XML is used
to exchange data between them.
XML Application
• XML processor, e.g. SOAP server,
XML Schema,
must validate the XML documents XML Processor DTD

against the XML grammar and XML Instance
XML Instance
pass the XML instance structure XML Instance
and payload to the application, e.g.
SOAP message. A validating XML processor, [2]


Session Outlines

 XML Overview
 XML Namespaces
 XML Schema


XML information set

• XML info set, provides a set of abstract data definitions to
represent the information in a well-formed XML document.
– Each well-formed XML document has an associated info set.
• The information set consists of information items.
– Each item describes an XML document part through a set of named
properties


Information item types of an XML information set, [2]

document
Property
children
Property
attribute
document
type element
declaration

Character
attribute
data


Information item types of an XML information set

• document, consists at least of one mandatory root element,
and:
– XML version info (optional) & encoding info for the document. These are
called XML declaration.
– Document type declaration: contains markup declarations provide the
grammar.
– These together is called prolog.


Information item types of an XML information set,
cont.

• element: identified by a name and has a set of associated
attributes.
• attribute: consists of a name and an associated value.
• character data: is an information item comprises the
payload of an XML document.
• comment: element and document information items may
contain comments.


Information item types examples [2]

• Comment info item “may span multiple lines”:
– <!– This is a comment -->
• Element info item:
– element may have no content e.g.: <address/> or
<address></address>

<address>
<name>Mr Ahmad Ahmad</name>
<street>11 Alquds Street</street>
<city>Ramallah</city>
<postal-code>100</postal-code>
<country>Palestine</country>
</address>



• An attribute is specified in the start tag of an element and
consists of a name-value pair.
– This example links an attribute named targetAddress with the
“PS” to the address elements:

<address targetAddress=“PS”>
<name>Mr Ahmad Ahmad</name>
</address>



• Document info item: look to the following prolog:
<?xml version=“1.0” encoding=UTF-16”?>
<! DOCTYPE address [<!– DTDs go here --> ]>
<address> <!– XML instances go here --> </address>
• Document type declaration identified by keyword DOCTYPE
must be identical to the corresponding root element


Information item types examples

• element content: if declared to be character data, this is
indicated by the term #PCDATA. “Parsed Character Data”
– Thus, a valid declaration would be:
<?xml version=“1.0” encoding=UTF-16”?>
<! DOCTYPE address [<!ELEMENT address
(#PCDATA)> ]>
• In an XML instance the address element could appear as
follows: <address>
Mr Ahmad Ahmad
11 Alquds Street
Ramallah
100
Palestine
</address>


Element content and mixed content

• We can combine elements and build nested element
declarations.
• DTD syntax provides 5 symbols used to describe manners of
combination.
• Assume e1, e2 and e3 to be elements:
– e1? : ? means none or one element e1.
– e1* : * means none, one or more element e1.
– e1+ : + means one or more than one element e1.
– e1, e2, e3 : , means list of element are chained.
– e1 | e2: means e1 or e2 can be chosen but not both.


address element can have this structure, [2]

address
Mandatory
n 1 1 1 1 Optional

name street city Postal-code country Containment
Relationship

0..1 1 1

title First-name Last-name

Source, [2]


A DTD describing the address structure, [2]

<?xml version=“1.0” encoding=“UTF-16”?>
<!DOCTYPE address [
<!ELEMENT address (name+, street, city, postal-code,
country)>
<!ELEMENT name (title?, first-name, last-name)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT first-name (#PCDATA)>
<!ELEMENT last-name (#PCDATA)>
<!ELEMENT street (#PCDATA)>
<!ELEMENT city (#PCDATA)>
<!ELEMENT postal-code(#PCDATA)>
<!ELEMENT country(#PCDATA)>
]>


An instance document could be as shown here

<address>
<name>
<title selectTitle=“Mr”/>
<first-name>Ahmad M.</first-name>
<last-name>Ahmad</last-name>
</name>
</address>


A valid address XML instance

<address targetAddress=“PS”>
<name>
</name>
</address>


Session Outlines

 XML Overview
 XML Namespaces
 XML Schema


XML Namespaces

• XML processor must be able to differentiate our XML
address instances from someone else’s address
instances.
– Identification using element type names is not sufficient.
• Some global naming mechanism is required.
• XML namespaces ensure that XML definitions are
unique.
• Using XML namespaces, XML elements can be
distinguished, even if they have identical names.

XML Namespaces concept

• An XML namespace comprises a collection of element
type names & attribute names.
• An XML namespace, is identified by a URI reference.
• The collection of element type names & attribute names,
belonging to the same namespace are identified by the
namespace URI reference.
• See next slide for namespaces example!

Identical markup belonging to different namespaces

http://companyx.com/ns/orders

<order>
<order-number>
<order-date>
<name>
<address>
http://clubx.com/ns/members
http://companyx.com/ns/employees
<member>
<employee-id> <member-id>
<dept-number> <member-since>
<name> <name>
<address> <address>

Source, [2], with modifications

Qualified names

• A name from a namespace appears in a document as a
qualified name (Qname).
• A Qname consists of a prefix and a local part.
• e.g. cX is the prefix and address is the local part:
cX:address
• Prefix selects the namespace and local part take care
of the naming within the scope of the namespace.

Declaring XML namespaces

• Done through the reserved namespace attribute xmlns.
• Also, can be done through xmlns: followed by a name
without colons.
• The value of the namespace attribute is the URI reference.
• Linking a namespace to a prefix, e.g.:
<address xmlns:cX=“http://companyx.com/ns/employees”>
– cX is the prefix for all qualified names belonging to the namespace
• Using a default namespace, e.g.:
<address xmlns=“http://companyx.com/ns/employees”>
– All subordinate elements are in the same default namespace, unless a
subordinate element overwrites the default namespace.

Declaring a namespace for the address document,
using prefix namespace attribute

<cX:address xmlns:cX=“http://companyx.com/ns/employees”
targetAddress=“PS”>
<cX:name>
<cX:title selectTitle=“Mr”/>
<cX:first-name>Ahmad M.</cX:first-name>
<cX:last-name>Ahmad</cX:last-name>
</cX:name>
<cX:street>11 Alquds Street</cX:street>
<cX:city>Ramallah</cX:city>
<cX:postal-code>100</cX:postal-code>
<cX:country>Palestine</cX:country>
</cX:address>

Using a default namespace name declaration

<address xmlns=“http://companyx.com/ns/employees”
targetAddress=“PS”>
<name>
</name>
</address>

An example for an entry of the phone book
maintained by the company

<phonebook xmlns=“http://companyx.com/ns/phonebook”
<location>Company X Office</location>
<roomNumber>03.02</roomNumber>
<!–- Extension -->
<officePhone>*2911111</officePhone>
</phoneBook>

XML namespaces and attributes

• Default namespaces are not applied to attributes that do not
have a prefix.
• The following example is a valid XML instance.
– Although the local part of the location element attribute is Identical.


<phonebook xmlns=“http://companyx.com/ns/phonebook”
<location department=“HR” phone:department=“HR”>
Company X Office</location>
</phoneBook>
</phoneOwner>

Session Outlines

 XML Overview
 XML Namespaces
 XML Schema


XML schema

• If we want to insert the roomNumber element to the phone
book as follows:
– A roomNumber value must start with 2 digits describing the building
floor, followed by a dot.
– Then, a 2 more digits to represent the room number on that floor.
• No way to specify this pattern through a DTD.
• XML schema allows us to express such a constraints.
• Various data types can be defined with XML schema and new
data types can be derived from existing ones.

An initial XML schema example

Type definition

It is a simple type <simpleType name=“roomNumberType”>
based on XML schema
<restriction base=“string”>
built-in type “string”
restricting the string to <pattern value=“[0-9]{2}.[0-9]{2}”/>
a distinct string pattern </restriction>
(the string pattern is </simpleType>
also called a facet)
<element name=“roomNumber” type=“roomNumberType”/>

Element declaration

The element named
roomNumber is of type
roomNumberType Source, [2]

The structure of an XML schema definition

• An XML Schema Definition (XSD) is itself an XML instance.
– An advantage of the XML schema.
• The top element of the xsd is name schema.
• The XML namespace for a schema definition is
http://www.w3.org/2001/XMLSchema, linked to
prefix xsd. Start a schema definition as:
<xsd:schema
xmlns:xsd=“http://www.w3.org/2001/XMLSchema”>
.. .. </xsd:schema>

Some of subordinate element types of schema
element.

• element: declares an element used in an XML instance.
• attribute: declares an attribute used in an XML instance.
• simpleType: this element defines a simple type, which is an
XML schema built-in type.
• complexType: this definition typically contains XML
elements and carry attributes, all declared within the type
definition.

XML schema containment structure of a simple
type definition

• Only one exclusive element must be contained in the superior
element.

simpleType
Mandatory
0..1 0..1
0..1 Optional

Exclusive
restriction list union
Containment
Relationship
n n n

“an approppriate
“an approppriate “an approppriate
“an approppriate “an approppriate
“an approppriate
facet”
facet” facet”
facet” facet”
facet”

12 applicable facets 6 applicable facets 2 applicable facets

Source, [2]

Attribute links between simple type XML schema
elements

restriction Linked-to
base base Relationship

XML Schema itemType itemType “a simple
list
Built-in type type”

memberTypes memberTypes
union

Source, [2]

A type definition for the title element

<xsd: simpleType name=“titleTypeUK”>
<xsd:restriction base=“xsd:string”>
<xsd:enumeration value=“Miss”/>
<xsd:enumeration value=“Mr”/>
<xsd:enumeration value=“Mrs”/>
<xsd:enumeration value=“Ms”/>
</xsd:restriction>
</xsd:simpleType>

Global elements may appear at the top level of an XML
instance:
<xsd:schema xmlns:xsd=“http://www.w3.org/2001/XMLSchema”>
. . .
<!–- “titleTypeUK” definition goes here -->
<xsd:element name=“title” type=“tns:titleTypeUK”/>
</xsd:schema>

A type definition for the first-name element

<xsd: simpleType name=“firstNameType”>
<xsd:pattern value=“[A-Z][a-z]*”/>
</xsd:restriction>
</xsd:simpleType>

minLength and maxLength
<xsd: simpleType name=“firstNameType”>
<xsd:pattern value=“[A-Z][a-z]*”/>
<xsd:minLength value=“2”/>
<xsd:maxLength value=“20”/>
</xsd:restriction>
</xsd:simpleType>

XML schema containment structure of a complex
type definition

• Only one exclusive element must be contained in the superior
element. And an arbitrary number of attribute.

complexType
Mandatory
n 0..1 0..1 0..1 0..1 Optional
Attribute/
Attribute sequence choice all group Exclusive
group
Containment
Relationship
n n n n

element
element element
element element
element element
element

Source, [2]

Complex type definitions

• The following XML schema presents a group named
nameGroup that is referred to within a complex type
definition, [2].


</xsd:sequence>
</xsd:group>

<xsd:complexType name=“addressType”>
<xsd:sequence>

<xsd:group ref=“nameGroup”/>
. . .
</xsd:sequence>
</xsd:complexType>

XML schema containment structure for deriving
types by extension

• simpleContent and complexContent elements must be
superior to either restriction or extension elements.

complexType

0..1 0..1 Mandatory
Simple Complex Exclusive
Content Content
Containment
Relationship

0..1 0..1 0..1 0..1

restriction extension restriction extension

Source, [2]

Linking XML schemas to XML instances

• schemaLocation attribute contains value pairs:
– The first value is a namespace.
– The second, provides a link to the schema used for validating elements and
attributes contained in this namespace.

Linking schemas to instances

• To link the address document instance to the address schema
via the schemaLocation attribute, we need to add this
attribute to the instance document.
Example

<cX:address
xmlns:cX=“http://companyx.com/ns/employees”
xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance
xsi:schemaLocation=“http://companyx.com/ns/employees
http://localhost/address.xsd”>
. . .




</cX:address>

Summary

During this session we have explained with examples the
following:
1. XML namespaces
2. XML schema

Next session will cover Xpath and Xquery.

References

1. Bray T, Paoli J, Sperberg-McQueen C M, Maler E. Extensible Markup Language
(XML) 1.0 (Second Edition), W3C Recommendation 6 October 2000,
http://www.w3.org/TR/REC-xml, 2000.
2. Olaf Zimmermann, Mark Tomlinson, Stefan Peuser, “Perspectives on Web services-
Applying SOAP, WSDL and UDDI to real-world projects, 2nd edition, Springer, 2005.

Pal gov.tutorial3.session2.xml ns and schema

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