Introduction1 3. Web Services (1/15) 1.Background a)The Future of the Web b)Machine-to-machine Web c)Current Web – what we need 2.Back to Data a)Semantic Web b)Web Services c)Representing Data 3.Web Services a)What are they? b)Simple Web Service c)Calling a Web service d)Separating the service from the implementation 4.Web Service Features and Deployment a)Features b)Development c)Deployment: The Service Oriented Architecture (SOA) approach

Introduction2 3. Web Services (2/15) 3.1 Introduction Currently, data is being exported as Web pages Next generation of the Web will be about data, not text Data Published as Web pages Data parsed from Web pages User Company ACompany B

Introduction3 3. Web Services(3/15) Looking Forward: What Do WE Need? Mac PC LinuxPC WindowsCE/PalmSolaris Addressing Scheme & Format e.g. HTML, Applets & Common Protocol HTTP Server FTP Server NNTP Server WAIS Gateway VMS Gateway Browsers Servers/Gateways

Introduction4 Mac PC LinuxPC WindowsCE/PalmSolaris Addressing Scheme e.g. DNS or P2P? & Format e.g. XML & Common Protocols e.g. SOAP Machine/Browser/Server Data Driven Web Mac PC LinuxPC WindowsCE/PalmSolaris Machine/Browser/Server

Introduction5 3. Web Services (5/15)  The Web allows many disparate information systems to serve data by creating an abstract imaginary space where differences do not exist.  For the machine-to-machine interoperable Web, we need the same kind of group of protocols that will allow machine to interoperate at the data level.  3 가지 핵심 기술 1.SOAP (Simple Object Access Protocol) 은 웹상의 객체들을 액세스하기 위한 마이 크로소프트의 프로토콜이다. 2.WSDL(web services description language) 은 특정 비즈니스가 제공하는 서비스 를 설명하고, 개인이나 다른 회사들이 그러한 서비스에 전자적으로 접근할 수 있 는 방법을 제공하기 위해 사용되는 XML 기반의 언어이다. 3.UDDI(universal description, discovery, and integration) 는 인터넷 상의 전 세계 비즈니스 목록에 자신을 등재하기 위한 XML 기반의 레지스트리이다.

Introduction6 3. Web Services (6/15) Representing Data and Semantics The focus on representing and exchange data using XML has led to two main thrusts in this direction.  The Semantic Web: is an extension of the current World Wide Web in which information is given well-defined meaning, better enabling computers and people to work in cooperation.  Web Services: are a software system designed to support interoperable machine-to-machine interaction over a network.

Introduction7 3. Web Services (7/15) BPELService Flow and Composition Semantics Trading Partner Agreement Service Agreement UDDI/WS Inspection Service Discovery UDDIService Publication WSDLService Description WS SecuritySecure Messaging SOAPMessaging HTTP, FTP, SMTP, MQ etc Transport

Introduction8 3. Web Services (8/15) 3.2 Web Services  Web services are a distributed systems technology that uses standard Internet protocol to move XML document between service processes.  Web services are software programs that enable applications to talk to each other remotely via XML messages A Minimal Web Service  A minimal Web service has three components: 1.The Services: a service is a software component which is capable of processing an XML document. 2.The Document: the XML document that is sent to a service which contains the application-specific information. 3.The Address: this describes the protocol binding (e.g., TCP or HTTP) along with the network address that can be used to access the service.

Introduction9 3. Web Services (9/15) Request XML Respons e XML A program sends a request to a remote Web service containing an XML message and (optionally) receives a response.

Introduction10 3. Web Services (10/15)  Web services can be used to exchange simple or extremely complex XML documents that can contain either document-oriented or procedure-oriented information.  Web services are interoperable and loosely coupled, which go hand in hand to create a powerful but flexible infrastructure for document exchange that can work on all platforms.

Introduction11 3. Web Services (11/15) Support Document Exchange: XML containing document-oriented or procedural- oriented information Standardization: based on standardized XML and supported globally by most major technology firms. Interoperability: i.e. XML is at the data transport level Loosely Coupled: the abstraction web server interface (WSDL) from its implementation decouples the logic of the client and the server. –makes it much easier to change back-end implementation without the client needing to update their code. Course-grained: course-grained model e.g. fine grained = Java method but Web Service typically combine several fine-grained operation to expose collective Supports RPC: support remote procedure calls (built into SOAP) via and XML- based protocol

Introduction12 3. Web Services (12/15) Web Services Development Green field: developer starts from scratch, creating not only the Web service but also the application functionality being exposed as a Web service. Bottom up: functionality being exposed as a Web service (i.e. the back-end application) already exists. Top down: start with an existing Web service interface and then create the application functionality capable of implementing that interface. Meet in the middle: combination – the Web services interface (abstract WSDL) and existing application code exists already –need to integrate them by creating a bridge

Introduction13 3. Web Services (13/15) 3.3 Service-Oriented Architectutre SOA is an example of a the composite computing model: “an architecture that that uses distributed, discovery-based execution to expose and manage a collection of service-oriented software assets” In this model: capabilities (i.e. software assets) should be dynamically discoverable should be a clear separation of the software's capabilities and its implementation should be possible to quickly assemble impromptu computing communities with minimal coordinated planning efforts, installation technicalities or human intervention.

Introduction14 3. Web Services (14/15)  3 Main Components SOAP: envelope for wrapping and transporting data WSDL: the web service interface i.e. its description UDDI: the repository i.e. the yellow pages of where you find information (e.g. like Jini LUS)

Introduction15 3. Web Services (15/15)