Web services / e-Services
Alessio Mura
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Web service definitions

W3C definition
A web service is a software system designed to support
interoperable machine-to-machine interaction over a network. It
has an interface described in a machine-processable format
(specifically WSDL). Other systems interact with the Web service
in a manner prescribed by its description using SOAP messages,
tipically conveyed using HTTP with an XML serialization in
conjunction with other Web-related standards

“Computer” - IEEE Computer Society Journal
Web services are Web-based applications composed of coarsegrained business functions accessed through the Internet

IBM
Web services are self-contained, modular applications that can be
described, published, located and invoked over a network,
generally, the Web
What is a web service

Functions
– A collection of operations
– Machine-to-machine interaction

Invoked / Accessed
– Well defined interface

Over a network (needs HTTP protocol)
– Intranet
– Web

Loosely coupled
– The service requester has no knowledge of the technical
details of the provider’s implementation
Why Web services


Logical evolution of object-oriented techniques to
e-business
Promoting interoperability by minimizing the
requirements for shared understanding
– Common program-to-program communications model
– Web services are platform and language independent

Enabling just-in-time integration
– Services are bound dinamically at runtime
– Systems are self-configuring, adaptive and robust

Reducing complexity by encapsulation
– All components of an application are services

Enabling interoperability of legacy applications
Evolutionary or
revolutionary?
Web services are to be viewed as an evolutionary
step towards software interoperability

Before Web services:
– Common Object Request Broker Architecture (CORBA)
– Distributed Component Object Model (DCOM)


Reasonable protocols for server-to-server
communications; weaknesses in client-server
communications on the Internet
Use of non-standard protocols
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Web services lifecycle





A Web service needs to be created and its
interface must be defined
A Web service needs to be published to one or
more intranet or Internet repositories for potential
users to locate
A Web service needs to be located to be invoked
by potential users
A Web service needs to be invoked to be of any
benefit
A Web service may need to be unpublished
when it is no longer available or needed
Web services interactions
Web services architectures

Web services
– W3C standard
– A universal client/server architecture
– Allows disparate systems to communicate with each other
without using proprietary client libraries

Each vendor or standards organization defines
Web services in a sligthly different way
– Architectural stack
Not all architectures of Web services are full interoperable
W3C Conceptual Web services stack
Discovery, Aggregation, Choreography, …
Web services Description (WSDL)
Messages
SOAP Extension
Reliability, Correlation, Transaction, …
SOAP
Communications
HTTP, SMTP, FTP, …
MANAGEMENT
Descriptions
Base Technologies: XML, DTD, Schema
SECURITY
Base Technologies: XML, DTD, Schema
Processes
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
XML–Based messaging



Exchange structured data between network applications
Allows software running on disparate operating systems, and
environments to make RPCs
Simple Object Access Protocol (SOAP)
– W3C standard
– Built over XML
Service Requestor
Application
Service Provider
Web service
SOAP
SOAP
Network Protocol
Network Protocol
SOAP message
Envelope
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Service description

The service provider defines all the specifications to
invoke the Web service
– Interface
– Operations and messages


The requestor and the provider don’t have to be
aware of each other’s underlying platform
Use of Web Service Description Language (WSDL)
– W3C standard (it was proposed by Microsoft and IBM)
– Based on XML documents
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Service publication
Makes a Web service description available to a
service requestor
 Direct publishing
– The service provider sends the service description directly to the
service requestor
– E-mail attachment, FTP site, CD-ROM distribution,…

Service description repository
– Local cache of service descriptions

Universal Description Discovery and Integration specification
(UDDI)
– Copyrigth by Accenture, Fujitsu-Siemens, HP, Intel, IBM,
Microsoft, Oracle, SAP, Sun Microsystems,…
– Organization for the Advanced of Structured Information
Standards (OASIS) standard
– A UDDI registry can be thought as a DNS for business
application
UDDI (1)
Defines a way to publish and discover information
about services

White pages : provide listings of providers (name,

Yellow pages : contains classification information

Green pages : info to interact with companies’ Web
text description, contact info and identifiers)
about the business entity and types of the services
the entity offers. E.g. Amazon can be a book seller
and a bibliographic information broker
Services (service description and binding
information)
UDDI (2)

Use of UDDI browsers
– http://www.soapclient.com/UDDISearch.html
– http://uddi.microsoft.com/search/search.aspx


Every Web service has an URI (Uniform
Resource Identifier)
Microsoft Web services
– The list of the Web service methods is displayed
when a browser loads the corresponding URI
– These methods are invocable from such list
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Service discovery
Acquires the service description and consumes it
 Acquiring
– With the direct publishing approach, the service requestor
caches the service description at design time
– The service requestor retrieves a service description at
design time or runtime from a service description
repository (UDDI)

Consuming
– The service requestor processes the description to invoke
the service

At design time or runtime
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Service flow


Choreography / Aggregation for W3C
Web services are composable
– The workflow will provide choreography
for automatic interaction between Web
services


W3C / IBM and Microsoft / Sun and
Oracle are competing for the standard
definitions of this layer
Work in progress
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Security
There are four basic security requirements:
 Confidentiality is the property that information is not made available
or disclosed to unauthorized individuals, entities, or processes, and
guarantees that the contents of the message are not disclosed to
unauthorized individuals
 Authorization is the granting of authority, which includes the granting
of access based on access rights and guarantees that the sender is
authorized to send a message
 Data integrity is the property that data has not been undetectably
altered or destroyed in an unauthorized manner or by unauthorized
users thereby insuring that the message was not modified
accidentally or deliberately in transit
 Proof of origin is evidence identifying the originator of a message or
data. It asserts that the message was transmitted by a properly
identified sender and is not a replay of a previously transmitted
message. This requirement implies data integrity
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Management
Management in this case means that a management
application can discover the existence, availability
and health of the Web service infrastructure, Web
services and service registries


It must be possible to manage Web services at all
levels of the conceptual Web services stack
The management interfaces should operate at the
service level, and not at the relatively low level of
the infrastructure
– Basic reporting of Web services infrastructure availability
– Information about performance, availability, events of Web
services
IBM Conceptual Web services stack
WSFL
Static -> UDDI
Service Discovery
Service Description
SOAP
XML–Based Messaging
HTTP, FTP, email, etc.
Network
Quality of Service
WSDL
Management
Service Publication
Security
Static -> UDDI
Service Flow
Quality of Service

In XML-Based Messaging level
– Reliable messaging : Ability of an infrastructure to deliver a
message once, and only once, to its intended target or to
provide a definite event, possibly to the source, if the
delivery cannot be accomplished

In service description level
– Maximun duration after the requestor expects the provider
to respond

In service composition or service flow level
– Expected execution time, timeout values,…

The Quality of Service issues and solutions for Web
Services are still emerging
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Web Services development
The development and deployment of Web services do
not require a particular technology in the underlying
platform


A common text editor can be used to develop Web
services
There are several development tools that allow to
easily develop Web services
– Microsoft Visual Studio .NET
– Sun ONE Studio
– IBM WebSphere Studio or Eclipse IDE with WSDK
– …
Web services with Microsoft
.NET

You have to
– Access to Internet Information Services (IIS)



In a local or remote machine
A server for web applications/services
The service repository of one or more service providers
– Create a Web service project in Microsoft Visual
Studio .NET


A Web service is composed by classes
Usage of keyword WebMethod for the public methods
invocable from the Internet
Web services in Microsoft
Visual Studio .NET
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Considerations

Web services standard today permits
application-to-application interoperability
– Server-to-server communications
– Client-server communications

The coordination of a set of Web services
working towards a common end is an open
issue
– Transaction-based applications
Service Oriented Architecture
(SOA)
From an IBM document on SOA
“…SOA presents the big picture of what you can do with Web
services…”
“…It can be based on Web services, but it may use other
technologies instead…”
“…A service in SOA is an application function packaged as a
reusable component for use in a business process…”

Software as a Service (SaaS)
– The key know-how involved is not who provides services
but what service a transaction requires at any particular
point
– Separate the possession and ownership of software from
its use
– Ultra-late binding
Service models
Supplier’s software
application service
Service layer (application
created on demand from
smaller services)
Service integration layer
Service transport layer
Current supply-led service model (it
provides only a predetermined
range of services from a remote
server)
Service transport layer
Proposed demand-led service
model (it has a service
integration layer inserted above
the transport layer)
Service integration layer

Service description, Service discovery
– A machine readable semantic description of the functionality
provided by the service

Service composition (Service flow)
– Automatic composition of Web services

Service negotiation
– The client and the provider must negotiate the service’s delivery
terms and conditions automatically



Contract’s duration
Transaction’s agreed security features
Service delivery
– Monitors whether the service is supplied within agreed terms and
conditions and suspends its provision if necessary
– Determines legal or nonfunctional parameters (cost, QoS,…)
Service-based software goals

Personalised
– Software capable of personalisation

Self-adapting
– Monitor and understand how software is being used

Fine-grained
– Small simple units
– High cooperation

Transparent
– Software has to be seen as a single abstract object
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
Software engineering
(considerations)


Internet age has ushered in a new era of highly dynamic and
agile organisations which must be in a constant state of
evolution if they are to compete and survive in an increasingly
global marketplace
There is still criticism of software systems and the methods
employed in their development, such as
– High cost
– Long time to market
– Poor flexibility
Many of these issues have been accentuated through the
widespread use of Internet and the acceleration of business
cycles
Web service engineering (1)
Web services are used for client-server
interactions (Now Web service = set of
classes)
A Web service can be used in an application
like a local class
A Web service is similar to a component,
the only difference is that it is accessible by
the Web
Component-based techniques

– Reuse of services
Web service engineering (2)

Highly flexible and agile software, that should be
able to meet changing business needs
– Classical software engineering methods are not adapted

Interdisciplinary view of software
– Trust and confidence : users need appropriate mental
models of software behaviour in order to have trust and
confidence in its performance
– Risk, responsibility, recovery : what happens when
software fails and, with the emergence of componentbased approaches, how to ensure accountability in
system development and evolution
– Software personalisation and adaptation
Web service engineering
(conclusions)


There is few material regarding this subject
which is still a matter of study
“Service-Oriented Software System
Engineering: Challenges and Practices” Zoran Stojanovic and Ajantha Dahanayake,
Delft University of Technology
–
–
–
–
–
Relevant theoretical background
Modeling notation
Tools
Development processes
Practical realisations
Summary

What is a Web service

Web services architectures

Web services development

Web services in the future

Web services engineering

e-Services
e-Services (1)
From Wikipedia, the free encyclopedia
 e-Service is a term usually referring to the provision of
services provided via the Internet (the prefix 'e' standing for
"electronic", as it does in many other uses)
 e-Service includes "e-commerce", although it may also include
non-commercial services
 Non-ecommerce e-Services include (at least some)
"eGovernment" services
From an article written by C.Peraire and D.Coleman
 An e-Service is some interaction offered to a user, across the
Internet, that has meaning and economic value
 An e-Component is a software module that provides one or
more e-Services. Thus, the e-Services provided by an eComponent constitute its interface
e-Services (2)
E-services is a business concept developed by Hewlett Packard
(HP)
 HP e-Services integration platform
– “… There are essentially no constraints on what the
platform can aggregate into the portal – Web-enabled
applications and informations stores, legacy applications,
and applications on open client/server systems …”
– Using HP's e-services concept, any application program or
information resource is a potential e-service; Internet
Service Providers (ISPs) and other companies are logical
distributors or access points for such services
 Cisco e-Services
– “…Cisco eServices provides a variety of voice processing
for your Cisco IP Telephony implementation…”


Cisco IP Integrated Voice Response (Cisco IP IVR)
Cisco IP Integrated Contact Distributor (Cisco IP ICD)
e-Services (conclusions)

The word e-Service:
– has a very general meaning
– is used to represent all web-based
applications

In some environments Web services
can be considered as e-Services
References (1)
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“Web Services Computing: Advancing Software Interoperability”
“Computer” IEEE Computer Society Journal October 2003 (Jen-Jao
Chung, Kwei-Jay Lin, Richard G. Mathieu)
“Turning Software into a Service” “Computer” IEEE Computer
Society Journal October 2003 (Mark Turner, David Budgen, Pearl
Brereton)
“Web Services architecture overview” IBM Web Services
Architecture Team - September 2000 - http://www106.ibm.com/developerworks/web/library/w-ovr/
“Web Services Conceptual Architecture (WSCA 1.0)” Heather
Kreger – IBM Software Group – May 2001 - www306.ibm.com/software/solutions/webservices/pdf/WSCA.pdf
“Web Services Architecture” – W3C Working Group – February 2004
– (David Booth, Hugo Haas, Francis McCabe, Eric Newcomer,
Michael Champion, Chris Ferris, David Orchard) –
http://www.w3.org/TR/2004/NOTE-ws-arch-200040211/
References (2)
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





“Web Services Architectures” – Tect – Judith M. Myerson
“Service-Oriented Architecture expands the vision of Web services,
Part 1” – IBM Corporation – Mark Colan –
www-106.ibm.com/developerworks/ library/ws-soaintro.html
“Service-Based Software: The Future for Flexible Software” – Keith
Bennett, Paul Layzell, David Budgen, Pearl Brereton, Linda
Macaulay, Malcolm Munro
“Modeling for E-Service Creation” Cecile Peraire and Derek Coleman
“Semantic Web services and Web services standards” – Sinuhé
Arroyo, Christoph Bussler and Rubén Lara – EEE04 –
http://deri.semanticweb.org/
“Component-Based Software Engineering” – Wilhelm Hasselbring
“Cisco eServices Architecture – Cisco IPCC Express Edition” Cisco
Systems –
http://www.cisco.com/en/US/products/sw/custcosw/ps1846/products_
administration_guide_chapter09186a00900eeac8.html
WSDL documents
<definitions>
<types>
Definition of a type (the datatypes used by the Web service)
</types>
<message>
Definition of a message (the messages used by the Web service)
</message>
<portType>
Definition of a port (the operation performed by the Web service)
</portType>
<binding>
Definition of a binding (the communication protocols used by the Web service)
</binding>
</definitions>
Glossary

XML: eXtensible Markup Language
– Example
<person id=1>
<name>
Alessio
</name>
</person>

DTD: Document Type Definition
– Define the legal building blocks of an XML document, they define
the document structure with a list of legal elements

XML Schema
– Provide a means for defining the structure, content and
semantics of XML documents