2. Web Services
What is Web Services?
How it Works.
Why use Web Services.
Web Services Components
Web Service Model
Advantages
Disadvantages
Conclusion
References
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3. Web Services
What is a Web Service?
A web service is a collection of open protocols and standards
used for exchanging data between applications or systems.
It support
machine-to-machine interactions over the
network.
Basic ideas is to build an platform and programming
language-independent distributed invocation system out of
existing Web standards.
Most standards
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defined by W3C.
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4. Web Services
Very loosely defined, when compared to CORBA(Common
object request broker architecture).
Inherit both good and bad of the web services.
◦ Scalable, simple, distributed
◦ But no centralized management system is inefficient, must be
tolerant of failures.
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5. Web Services
How does a web services work?
- The client sends a request
- Request encoded in XML
- Function (GET, POST…) in the file
- The server decodes the file
- The function is executed
- A new XML file is encoded
and re-send to the client.
- Clients and servers communicate over
the HyperText Transfer Protocol (HTTP).
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6. Web Services
Why use web Services?
Web services provide a clean separation between a capability
and its user interface.
This allows a company (Google) with a sophisticated
capability and amounts of data to make that capability
available to its partners.
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8. Web Services
XML Concept
XML stands for EXtensible Markup Language.
XML is a markup language much like HTML.
XML was designed to describe data.
XML tags are not predefined. You must define your own
tags.
The prefect choice for enabling cross-platform data
communication in Web Services.
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9. Web Services
Web Services Description
Language(WSDL)
Defines what your service does and
how it is invoked.
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10. Web Services
WSDL overview
WSDL stands for Web Services Description Language
WSDL is an XML based protocol for information exchange
in
decentralized and distributed environments.
WSDL is the standard format for describing a web service.
WSDL definition describes how to access a web service and
what operations it will perform.
WSDL is a language for describing how to interface with
XML-based services.
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11. Web Services
WSDL( Continue…)
WSDL is an integral part of UDDI, an XML-based worldwide
business registry.
WSDL is the language that UDDI uses.
WSDL was developed by Microsoft and IBM.
Elements of WSDL:
<types>
A container for data type definitions used by the web
service
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12. Web Services
WSDL( Continue…)
<message>
A typed definition of the data being communicated.
<port Type>
A set of operations supported by one or more
endpoints.
<binding>
A protocol and data format specification for a
particular port type
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13. Web Services
Simple Object Access
Protocol(SOAP)
A message format for exchanging
structured, typed information
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14. Web Services
SOAP
SOAP stands for Simple Object Access Protocol.
SOAP is a protocol for accessing web services.
SOAP is based on XML.
SOAP provides a way to communicate between applications
running on different operating systems, with different
technologies and programming languages.
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15. Web Services
SOAP Charactristics
SOAP has three major characteristics:
Extensibility – security and WS-routing are among the
extensions under development.
Neutrality - SOAP can be used over any transport protocol
such as HTTP, SMTP or even TCP.
Independent - SOAP allows for any programming model .
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16. Web Services
UDDI Overview
UDDI is a platform-independent framework for
describing services, discovering businesses, and
integrating business services by using the Internet.
UDDI stands for Universal Description, Discovery and
Integration.
UDDI is a directory for storing information about web
services.
UDDI is a directory of web service interfaces described
by WSDL.
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17. Web Services
Web service model
The Web Services architecture is based upon the interactions
between three roles:
◦ Service provider
◦ Service registry
◦ Service requestor
The interactions involve the:
◦ Publish operations
◦ Find operation
◦ Bind operations.
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18. Web Services
web service model(cont…)
The web services model follows the publish, find and bind
paradigm.
Web Service
Registry
Web Service
provider
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Web Service
Client
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19. Web Services
Advantages
Interoperability - This is the most important benefit of Web
Services. Web Services typically work outside of private
networks.
usability - This gives your applications the freedom to chose
the Web Services that they need. This allows you to develop
services and/or client-side code using the languages and tools
that you want.
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20. Web Services
Advantages(cont…)
Reusability - Web Services provide not a component-based
model of application development, but the closest thing
possible to zero-coding deployment of such services.
Deployability - Web Services are deployed over standard
Internet technologies.
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21. Web Services
Disadvantages
Distributed transactions:
if the environment requires distributed transactions with
resources, it should be studied and tested with standard
solutions based on BTP, WS-Transactions, and WSCoordination.
Quality of Service (QoS):In case of a mission-critical
solution, the service providers must examine the reliability
and performance of the service in uncertain conditions for
high availability.
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22. Web Services
Disadvantages(cont…)
Security: Web services are exposed to the public using httpbased protocols.
As Web services is publicly available, it must be
implemented using authentication and authorization
mechanisms and using SSL-enabling encryption of the
messages for securing the usage.
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23. Web Services
Conclusion
This aimed to give an overview of recent progress in
automatic Web services composition.
At first, we propose a three-step model for Web services
composition process.
The composition model consists of service
presentation,translation,process generation, evaluation and
execution. Each step requires
different languages, platforms and methods.
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