WEB SERVICES DAVIDE ZERBINO

Summary: Introduction Definition Web Service Model Web Service Architecture Web Service in action Advantages Web Service Development Lifecycle Tools References

Introduction A Software Service is a something that accepts digital requests and returns digital responses e.g. C function, a Java Object A computer application can be thought of as a well-orchestrated set of services Web Services are a new breed of software component that is a language, platform, and location indipendent Is accessible over the web Web services are an abbrevation for Web of Services Distributed applications will be assembled from a web of software services

Web Service Is registred and can be located through a Web service registry. Communicate using XML message over standard Web protocols. Support loosely-coupled connections between systems.

Definition of Web Service “A Web service is an interface that describes a collection of operations that are network-accessibile through standardized XML messaging.” Heather Kreger IBM Software Group

The Web Services Model The Web service architecture is based upon the interactions between three roles: Service Registry application that is looking for and invoking an interaction with a service owner of the services searchable registry where service provider publish their service descriptions and where service find service Service registry Service Requestor Service Provider

The Web Services Model Others element are: Service Description Service Registry Requestor Provider Service registry Service

The Web Services Model Others element are: Description Contains details of the interface and implementation of the service Service registry It is a software module deployed on the network-accessible platforms provided by the service provider

The Web Services Model The interactions involve the publish, find and bind operation Service Registry Requestor Provider Find Publish Service registry Bind

The Web Service Stack Security Management Quality of services HTTP, FTP, email, MQ, etc SOAP WSDL UDDI WSFL Standard Tecnologies Requirements Network Service Description XML-Based Messaging Service publication Service Discovery Service Flow

Web services must be network-accessible The Network Web services must be network-accessible For its ubiquity HTTP is the standard network protocol for internet-available Web Services Others network protocols are SMTP, FTP and for intranet domain: MQSeries, CORBA

XML-based Messaging Represent the use of XML as the basis for the messaging protocol The current industry standard for XML messaging is SOAP IBM, Microsoft, Sun and others submitted SOAP to the W3C SOAP (Simple Object Access Protocol) Is a simple and lightweight XML-based mechanism for exchanging structured data beetween network applications

SOAP Lightweight communication protocol For communication between applications one-way, request/response, multicast, etc.. Designed to communicate via HTTP Not tied to any component technology Not tied to any programming language Based on XML Simple and extensible

SOAP SOAP consists of three parts: An envelope that defines a framework for describing what is in a message A set of encoding rules for expressing istances of application-defined data types A convention for representing remote procedure calls and responses

SOAP 1 4 3 2 web service Application SOAP Network protocol Request/Response 1 4 3 2

Service Description: From XML to Web services Service provider comunicates all the specifications through service description The service description combined with SOAP infrastructure hides details as platform, programming language from the service requestror’s application and the service provider’s Web Service Web service uses WSDL for base-level service description

WSDL WSDL: Web Service Definition Language is an XML-based language used to define Web Services and describe how to access them Industry standard W3C Service Implementation Definition Interface Service Port Binding PortType Message Type

Discovery and Publication: UDDI Stands for Universal Description, Discovery and Integration Defines a way to publish and discover information about web services Collaboration between Microsoft, IBM, Ariba that resulted in the creation of web service registry Not standard

UDDI Defines a data structure standard for representing service description information in XML The core component of the UDDI project is the UDDI business registration, an XML file used to describe a business entity and its Web services

UDDI The UDDI Business Registry can be used at a business level To check whether a given partner has particular Web service interfaces. To find companies in a given industry with a given type of services. To locate information about how a partner or intended partner has exposed a Web service in order to learn the technical details required to interact with that service

WSFL Overview Web Service Flow Language (WSFL) is an XML language for the description of Web Services Composition It is possible to produce web services by composing web services Intra-enterprise web services might collaborate to present a single Web Service Interface to the public Web services from different eneterprises might collaborate to perform business to business transactions Service Flow described how service-to-service communications, collaborations and flows are performed.

WSFL Overview Composition of Service Flow Model – execution sequence of activities Global Model – Interactions of services Recursive Composition – scalability It is layered on the top of Web Services Description Language(WSDL) that is used for description of service interface and their protocol bindings

Web Service in Action: B2B Customer Supplier Credit Bureau Check validity Service Account Service Warehouse

Advantages Interoperability: Any web services can interact with any other web service Ubiquity: Web services communicate using HTTP and XML. Low Barrier to Entry: The concepts behind web services are easy to understand and toolkits are frely available from many vendors Industry Support: All the major vendor are supporting SOAP and the surrounding web services standards

Web Services Development Lifecycle The development lifecycle can have four phase: BUILD : development and testing of the web service implementation definition of the services interface description definition of the service implementation description DEPLOY : publication of the services interface and service implementation RUN : The web service is available for invocation The web service is fully deployed, operational and network-accessible from the services provider Now the service requestor can perform the find and bind operations MANAGE : Covers ongoing management and administration of the web services application

Tools Microsoft SOAP Toolkit 2.0 Microsoft Visual Studio .NET and .NET Framework Apache SOAP Toolkit and AXIS IBM Web Services Toolkit SUN JavaTM 2 Platform, Enterprise Edition (J2EE)

Example: Airport Weather Service Interface: getLocation() getWind() getTemperature() getSky() getPressure() getHumidity() getSummary() Airport Weather More informations: Web Interface: http://live.capescience.com/AirportWeather/index.html

References About SOAP : http://www.w3c.org/TR/soap About WSDL : http://www.w3c.org/TR/wsdl About UDDI : http://www.uddi.org About WSFL : http://www.ibm.com/software/webservices

Other Papers About Web service Architecture: Web Services Conceptual Architecture (WSCA 1.0) -Heather Kreger - IBM SW Group About Web service development lifecycle: Web Services Development Concepts (WSDC 1.0) -Peter Brittenham- IBM SW Group About Web service model: Web Services : Building Blocks for Distributed System -Graham Glass -

The End

Web Server in Action (2/2) HTTP WSDL SOAP Application Interoperability

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