A SURVEY PAPER ON SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

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SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

A SURVEY PAPER ON SERVICE ORIENTED
ARCHITECTURE APPROACH FOR WEB SERVICES

Diana Geangalau

(dgeangal@utdallas.edu)





Computer Science Department

The University of Texas at Dallas


Software Architectural Design





Acknowledgement:

The specific implementations of SOA principles into Web Services are taken from
Java Web
Services Architecture
by James McGovern, Sameer Tyagi, Michael Stevens, and Sunil Mathew, published by
Morgan Kaufmann Publishers. All rights reserved.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

2

WEB SERVICES
-

DEFINITIONS




The term
Web Services

describes a standardized way of integrating
Web
-
based applications.



“Web Services

is the technology that allows for different applications
from different sources to communicate with each other without time
-
consuming custom coding, and because all communication is in XML,
Web services are not tied to any one operating system or programming
language.”
-

Webopedia



Web Services

are primarily used as a means for businesses to
communicate with each other and with clients.



Web Services

are inherently distributed as opposed to the
Client/server applications that are primarily data
-
centric in nature.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

3

WEB SERVICES ARCHITECTURE



UDDI
-

Universal Description Discovery and Integration


Finds the Internet location of the requested web service.


The "yellow pages" of Web Services on Internet.


WSDL
-

Web Services Description Language



Web services provider advertises the provided services so
that the client applications obtain information about a web
service prior to accessing and using the web service.

SOAP
-

Simple Object Access Protocol


The channel used for communication between a web
services provider application and a client application.

XML
-

Extended Markup Language


Is a meta language that has a well
-
defined syntax and
semantics to provide the means to format the messages into
XML documents.

HTTP


Hyper Text Transfer Protocol


Ensures that web services provider applications and client
applications can communicate using the Internet as the
backbone.



Web Service layers

Transport (HTTP)

Encoding (XML)

Standard structure (SOAP)

Description (WSDL)

Discovery (UDDI)

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

4

USING WEB SERVICES


The client application queries the Web Services WDSL file in order to find out what the service can provide and how.

Then the client sends a request to the service at its given URL using the SOAP protocol over HTTP.

The service receives the request, processes it, and returns a response.

XML

Client

WDSL

proxy

WDSL

WDSL



WDSL

WDSL

Web Service

WDSL

stub

4

UDDI
Server

response

request

1 HTTP +SOAP

2

3

1. Communication
protocol

2. Message format

3. Description
language

4. Discovery
mechanism

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

5

STEPS TO CREATE A WEB SERVICE

Define the services that
will be provided

Implement the functionality
behind the services

Deploy the service
provider application

Publish the Web services
with a directory service

Wait for processing client
requests

Service Provider

Identify the services that will
be required

Locate the Web service by
querying a directory service

Send the request to the
service

Receive the response from
the service

Service Client

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

6

SERVICE ORIENTED ARCHITECTURE
-

DEFINITION


A

Service
-
Oriented Architecture

is essentially a collection of services that
communicate with each other. The communication can involve either simple
data passing or it could involve two or more services coordinating some
activity.



The

Service
-
Oriented Architecture

for Web Services has:


a standard way for communication


a uniform data representation and exchange mechanism


a standard meta language to describe the services offered


a mechanism to register and locate web services
-
based applications

Service
Provider

Service
Consumer

service request

service response

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

7

SERVICE ORIENTED ARCHITECTURE
-

ENTITIES



Service Consumer


The service consumer is an application, service, or
some other type of software module that requires a
service.


Service Provider


The service provider is the service, the network
-
addressable entity that accepts and executes requests
from consumers.



Service Registry


A service registry is a network
-
based directory that
contains available services.


Service Contract


The contract specifies the way in which the service
consumer and the service provider will interact. It
specifies the format of the request and response from
the service
.


Service Proxy


The service proxy is provided by the service provider to
the service consumer. It enhances the service
performance by caching at the service consumer site
the remote references and data. Thus the subsequent
service calls do not require additional registry calls.

Registry





Service
Provider





Service
Consumer





Contract




register

find

bind and execute

The consumer of a service asks the registry
for the service that matches its criteria.



If the registry has such a service, it gives the
consumer a contract and the endpoint
address for the service.


The consumer than accesses the service.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

8

PRINCIPLES
-

MODULARITY

The modularity allows the services to be aggregated into an application with a few
well
-
known dependencies.



The service application can be decomposed into many smaller modules in which
each module is responsible for a single, distinct function within the application.



The software services are reusable so that they can be combined with other
services to produce new systems.



The functions of a service can be understood by any client without having any
knowledge of other services, thus any consumer is able to find and decide to use a
service at any time.



A service hides the information about its internal design therefore any changes
made internally will not create a domino effect to affect other services.



Faults in the operation of a service do not impact the operation of a client or other
service or the state of their internal data, thus the faults do not cascade from the
service to other services or consumers.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

9

PRINCIPLES


LOOSE COUPLING

Coupling refers to the number of dependencies between modules. The loosely coupled
modules have a few well
-
known dependencies.



The consumer of the service does not need detailed knowledge of the service before
invoking it, thus the consumer and provider are loosely coupled.



SOA accomplishes loose coupling through the use of contracts and bindings.


A consumer asks a third
-
party registry for information about the type of service it
wishes to use.


The registry returns all the services it has available that match the consumer's criteria.


The consumer chooses which service to use, binds to it, and executes the method on it,
based on the description of the service provided by the registry.



The consumer does not depend directly on the service's implementation but only on
the contract the service supports therefore a a service may be both a consumer and
a provider of some services.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

10

PRINCIPLES


ENCAPSULATION


All components in Web Services are services.



The type of behavior a service provides is important not how it is implemented.



A WDS (Well
-
Defined Service) document is the mechanism to describe the behavior
encapsulated by a service: service category, service description, and expiration
date, as well as business information about the service provider, such as company
name, address, and contact information.




System complexity is reduced because the application designers do not have to
worry about implementation details of the services they are invoking.



Substitution of different implementation of the same type of service, or multiple
equivalent services, is possible at runtime.



The behavior of a service is encapsulated and extended by providing new services
with similar service descriptions.


SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

11

CONCLUSIONS



Web Services are the preferred standards
-
based way to realize
Service Oriented Architecture.



The use of Service Oriented Architecture for Web Services offers
potential for lower integration costs and greater flexibility.



Service Oriented Architecture separates the service interface (the
what) from its implementation (the how).



Such services are consumed by clients that are not concerned
with how these services will execute their requests.



Web services are the next step in the Web's evolution, since they
promise the infrastructure and tools for automation of business
-
to
-
business relationships over the Internet.

SERVICE ORIENTED ARCHITECTURE APPROACH FOR WEB SERVICES

12

REFERENCES




Java Web Services Architecture
(ISBN: 1
-
55860
-
900
-
8), by James McGovern, Sameer Tyagi, Michael Stevens, and
Sunil Mathew, published by Morgan Kaufmann Publishers. © Copyright Morgan Kaufmann Publishers. All rights
reserved.


Service
-
oriented architecture

Perrey, R.; Lycett, M.;

Applications and the Internet Workshops, 2003. Proceedings. 2003 Symposium on

27
-
31 Jan. 2003 Page(s):116
-

119


Modeling and design of service
-
oriented architecture

Stojanovic, Z.; Dahanayake, A.; Sol, H.;

Systems, Man and Cybernetics, 2004 IEEE International Conference on

Volume 5,


10
-
13 Oct. 2004 Page(s):4147
-

4152 vol.5


Deployment of service oriented architecture for a business community

Baglietto, P.; Maresca, M.; Parodi, A.; Zingirian, N.;

Enterprise Distributed Object Computing Conference, 2002. EDOC '02. Proceedings. Sixth International

17
-
20 Sept. 2002 Page(s):293
-

304


A service management framework for service
-
oriented enterprises

Ying Huang; Kumaran, S.; Chung, J.
-
Y.;

e
-
Commerce Technology, 2004. CEC 2004. Proceedings. IEEE International Conference on

6
-
9 July 2004 Page(s):181
-

186


Extending the Web services model to it services

Stern, A.; Davis, J.;

Web Services, 2004. Proceedings. IEEE International Conference on

6
-
9 July 2004 Page(s):824


825


Web services oriented architecture for electronic commerce

Huinan Xu;

Engineering Management Conference, 2003. IEMC '03. Managing Technologically Driven Organizations: The Human
Side of Innovation and Change

2
-
4 Nov. 2003 Page(s):479
-

483


http://www.service
-
architecture.com/web
-
services/articles/index.html


http://www.sys
-
con.com/webservices/


http://searchwebservices.techtarget.com/originalContent/0,289142,sid26_gci882438,00.html