Kemal Baykal Rasim Ismayilov WEB SERVICES Kemal Baykal Rasim Ismayilov

Web Services(1) A software system which connects the machines over a network in an interoperable manner The main idea is to make the communication between business systems and clients and also within each other. The main advantage of Web services is to allow organizations to communicate data without knowing each other's IT systems behind the firewall.

Web Services(2) Does not provide GUI unlike the server/client systems. Share business logic, data and processes through a programmatic interface Normally the applications interact with each other, not with users But you can add a GUI to gain extra functionalities over the users.

Applications in Web Services XML is used to tag the data SOAP is used to transfer the data WSDL is used for describing the services available UDDI is used for listing which services are available

XML (Extensible Markup Language) It is classified as an extensible language because it allows its users to define their own tags Main purpose is to facilitate the sharing of structured data across different information systems It is the language both machines and human beings can understand easily It is used both to encode documents and serialize data

SOAP (Service Oriented Architecture Protocol) is a protocol for exchanging XML-based messages over computer networks used to encode the information in Web service request and response messages before sending them over a network SOAP messages are independent of any operating system or protocol may be transported using a variety of Internet protocols, including SMTP, MIME, and HTTP

SOAP elements Envelope element, identifies the XML document as a SOAP message (required) Header element, contains header information (optional) Body element, contains call and response information (required) Fault element, provides information about errors that occurred while processing the message (optional)

SOAP’s Protocols SOAP uses SMTP and HTTP as an application layer protocol for transport. HTTP is used more because it works well with today's Internet infrastructure. SOAP works well with network firewalls.

SOAP Advantages Disadvantages SOAP allows the use of different transport protocols. Using SOAP allows easier communication behind proxies and firewalls Because of the verbose XML format, SOAP can be considerably slower than technologies such as CORBA. This is not the case when only small messages are sent Many SOAP implementations limit the amount of data that can be sent.

WSDL (Web Services Description Language) an XML-based language that provides a model for describing Web services describe Web service's capabilities as collections of communication endpoints capable of exchanging messages an integral part of UDDI and the language that UDDI uses is used to describe what a web service can do, where it resides, and how to call it

WSDL’s elements (1) Types : a container for data type definitions using some type system Message: an abstract, typed definition of the data being communicated Operation: an abstract description of an action supported by the service Port Type: an abstract set of operations supported by one or more endpoints

WSDL’s elements (2) Binding: a concrete protocol specification for a particular port type Port: a single endpoint defined as a combination of a binding and a network address Service: a collection of related endpoints

WSDL’s Properties is a template for how services should be described and bound by clients is often used in with SOAP and XML Schema to provide web services over the Internet A client program connecting to a web service can read the WSDL to determine what functions are available on the server was developed by Microsoft and IBM

UDDI (Universal Description, Discovery and Integration) a Web-based distributed directory that enables businesses to list themselves on the Internet and discover each other is platform independent is XML based designed to be interrogated by SOAP messages to provide access to WSDL documents describing the protocol bindings and message formats

UDDI Components White Pages: address, contact, and known identifiers Yellow Pages: industrial categorizations based on standard taxonomies Green Pages: technical information about services exposed by the business

UDDI Data Types businessEntity: The top level structure, describing a business or other entity for which information is being registered bindingTemplate: Information necessary to use specific services which may have bindings to one or more protocols.. businessService: Description of a set of services which may contain one or more bindingTemplates. tModel: Technical “finger print” for a given service which may also function as namespace to identify other entities

Additional Specifications for WS (1) WS Security WS Reliability WS Reliable Messaging WS Addressing WS Transaction

Additional Specifications for WS (2) They are all specified by OASIS community (Microsoft, IBM, VeriSign and Forum Systems) They use different technology (xml) not like traditional http So the technology for security, reliable messaging, reliability, addressing and transactions differ. They are XML based. For example, as an alternative to use HTTPS to secure the channel, it uses XML based technologies such as XML Signature, XML Encyription,...

Web Services vs Java RMI interoperable transfer by xml files (knowing what goes in wire) easy access of enterprise business operations platform-independent, easy interaction through different applications needs large bandwidths better performance transfer by bytes integrated with Java less CPU&memory usage doesn’t need large bandwidths

Alternative Solution! dual technology can be used Web Service implementation for external users an alternative higher performance variant of internal use by Java RMI

References http://www.ribomation.com/riboutils/webservices-performance/article.html http://mercury.it.swin.edu.au/ctg/AWSA04/Papers/gray.pdf http://en.wikipedia.org/wiki/Web_service http://www.webopedia.com/TERM/W/Web_services.html