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DEFINITIONSimple definitions:• “a Web Service is an application component accessible over open protocols”• “Web services are typically application programming interfaces (API) or web APIs that can be accessed over a network, such as the Internet, and executed on a remote system hosting the requested services”
INTRODUCTION• Web Services are a new breed of Web application. They are Self-contained Self-describing modular applications• Web Services perform functions, which can be anything from simple requests to complicated business processes.• Once a Web service is deployed, other applications can discover and invoke the deployed service
TERMINOLOGIESService provider: – The collection of software that provides a Web service.Service provider application: – An application that is used in a service provider. – It provides the business logic component of service provider.Service requester: – The collection of software that is responsible for requesting a Web service from a service provider.Service requester application: – An application that is used in a service requester. – It provides the business logic component of a service requester.
THE 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.
THE WEB SERVICE MODEL (cont) Web Service Web Service Provider Client
ROLES• WEB SERVICE REGISTRY: – It is a software component that supports the run time discovery and evaluation of resources such as services, datasets, and application schemes.• WEB SERVICE PROVIDER: – The service provider is the business that provides access to the Web service and publishes the service description in a service registry.• WEB SERVICE CLIENT: – The service client finds the service description in a service registry and uses the information in the description to bind to a service
WEB SERVICE EXAMPLESGOOGLE DOCUMENT:• Google Docs is a free, Web-based word processor, spreadsheet, presentation, form and data storage service offered by Google.• It allows users to create and edit documents online while collaborating in real-time with other users.• Google Docs combines the features of Writely and Spreadsheets with a presentation program incorporating technology designed by Tonic Systems.
Amazon S3 (Simple Storage Service)• It is an online storage web service offered by Amazon Web Services.• It provides unlimited storage through a simple web services interface.• Details of S3s design are not made public by Amazon.• According to Amazon, S3s design aims to provide scalability, high availability, and low latency at commodity costs.• Subscribers can choose to keep their data private or make it publicly accessible.• Users can also encrypt data prior to storage.• Rights may be specified for individual users.
Amazon Elastic Compute Cloud (Amazon EC2)• It is a web service that provides resizable compute capacity in the cloud.• Designed to make web-scale computing easier for developers.• It’s simple web service interface allows to obtain and configure capacity with minimal friction.• And it provides with complete control of our computing resources and lets run on Amazon’s proven computing environment.
Universal Description, Discovery and Integration (UDDI)• It is a specification for distributed Web-based information registries of Web services.• UDDI is also a publicly accessible set of implementations of the specification• It allow businesses to register information about the Web services they offer so that other businesses can find them.• The specification is published by OASIS
SOAP• Formerly an acronym for Simple Object Access Protocol.• A lightweight protocol for exchange of information in a decentralized, distributed environment.• IT IS AN XML BASED PROTOCOL THAT CONSISTS OF THREE PARTS: An envelope that defines a framework for describing what is in a message and how to process it. A set of encoding rules for expressing instances of application-defined data types. A convention for representing remote procedure calls and responses.• SOAP can be used with other protocols, such as HTTP.
WSDL• Web Service has an interface described in a machine- processable format (specifically, Web Service Description Language, or WSDL).• An XML application for describing Web services.• It is designed to separate the descriptions of the abstract functions offered by a service, and the concrete details of a service, such as how and where that functionality is offered.
XML• Extensible Markup Language (XML) is a set of rules for encoding documents in machine-readable form.• It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards.• XMLs design goals emphasize simplicity, generality, and usability over the Internet.
HTTP• The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems.• HTTP is the foundation of data communication for the World Wide Web.• HTTP functions as a request-response protocol in the client-server computing model.
BENEFITS• Web services provide interoperability between various software applications running on disparate platforms/operating systems• Web services use open standards and protocols• By utilizing HTTP web services can work through many common firewall security measures without requiring changes to the firewall filtering rules. Other forms of RPC may more often be blocked
Contd..• Web services allow software and services from different companies and locations to be combined easily to provide an integrated service• Web services allow the reuse of services and components within an infrastructure• Web services are loosely coupled thereby facilitating a distributed approach to application integration
LIMITATIONS• Web services standards features such as transactions are currently nonexistent or still in their infancy compared to more mature distributed computing open standards such as CORBA.• Web services may suffer from poor performance compared to other distributed computing approaches such as RMI, CORBA, or DCOM.
SUMMARY• The Web services framework is being defined, standardized and supported by the industry at a record pace.• Broad industry acceptance and standard compliance will make it ubiquitous.• Will bring an unprecedented level of interoperability to Web applications.• The benefits of Web services, however, are not limited to the Web!