1 Introduction CSIE, Da-Yeh University

2 History of Software Development Traditional Programming Paradigm  Behind schedule, costly, and unreliable. Structured Programming (1970’s)  Systematical analysis of the problems.  Does not mirror the real world entities. Object Oriented Programming (1980’s – 1990’s)  Object technique is a packaging scheme to create software units.  Use classes to represent the real world entities.  Web service take advantages of the OO technology.

3 Component-based Development A component is a piece of software that satisfies  It must be deployable on its own  It must publish and adhere to a programming interface.

4 Component-based Development The limitation of using components  It takes a lot more effort to develop components that is reusable.  It is difficult to find the right components.  It is hard to coordinate the releases of new components.

5 Client Server Design

6 Internet Design

7 Application Server Architecture

8 Distributed Computing The computing tasks are distributed over networks. Components extended at different computers must be able to communicate with each other.  Interface and response  Security Client Infrastructure Proxy Application internet

9 Distributed Computing Different technology  Object Management Group (OMG) – Common Object Request Broker Architecture (CORBA)  Microsoft – Distributive Component Object Model (DCOM)  IBM – Distributive System Object Model (DSOM)  Sun Micro – Remote Method Invocation (RMI) Components from different technology communicate with each other through a bridge.  COM/CORBA bridge  Poor interoperability

10 Distributed Computing Infrastructure Microsoft’s DCOM  Shipped with versions of Windows NT beginning with version 4.0 and including Windows  Provide both local and remote COM capabilities. It is now an inherent part of Win32-based platforms.

11 N-tier Web-based Application The client-tier uses browsers as the user interface. The middle-tier provides all the business logic and processes. The information-tier is the information tier. Client-tierMiddle-tier Information-tier data

12 Alternative to Web Service Screen Scraping: retrieving data from other HTML documents. What are the disadvantages of using screen scraping? HTML Web page Middle TierDatabase Application

13 Web Service Technology Address the issue of poor interoperability. Use open standard. Easy to debug.  Web services use text-based protocols. Use XML as the standard for exchanging information.

14 Definition of Web Service Web services are software programs that use XML to exchange information with other software via internet protocol. Characteristics of web service  Web services are programmable.  Web services are based on XML.  Web services are self-describing (WSDL).  Web services are discoverable (UDDI).

15 Web Service Architecture Protocols The core principles drive the design and implementation of WS architecture protocols  Message orientation  Protocol composability  Autonomous services  Managed transparency  Protocol-based integration

16 Benefits over Distributed Computing Companies can expose and access web services using technology already in place. Web service is more interoperable. Nearly all major software vendors have agreed to use the same core standards.

17 Challenge of the Web Service SOAP, WSDL, UDDI are still in draft. Royalty fees may required for some standards. Lack of standard security procedure. Defining and guaranteeing QoS.  Slow response time  Infrequent update  Inability to handle large number of requests

18 Web Service Architecture UDDI Registry WSDL Document client Web Service Query Registry to locate service ‚Refer to WSDL documents ƒAccess WSDL documents „Provide data to interact with web service …Send SOAP message request †Send SOAP message response

19 Web Service Terminology - SOAP SOAP (Simple Object Access Protocol)  A common way to package messages that are exchanged between two processes.  A common set of serialization techniques for the data that is exchanged.  A mechanism that allows Remote Procedure Calls (RPC) to be made across a heterogeneous set of platforms.

20 Web Service Terminology – XSDL XSDL (XML Schema Definition Language)  XSDL defines the layout of and the constraints on an XML document.  XSDL supplants a previous standard known as Data Type Definition (DTD).

21 Web Service Terminology - UDDI UDDI (Universal Description, Discovery, and Integration) registry  The most commonly known method of discovering Web services.  UDDI registry’s structure is similar to the phone book White page: list contact information and descriptions of companies. Yellow page: provide classification information about companies and details on companies’ electronic capability. Green page: list technical data regarding services.

22 Web Service Terminology - WSDL WSDL (Web Service Description Language)  It provides details about the functionality that is implemented, which messages are used to request the service, and the sequence in which the messages are exchanged.  It is XML-based format.  Similar to the documentation to the ActiveX components.

23 Web Service Terminology - others XML ( eXtended Markup Language)  The main language used in Web service. GXA (Global XML Architecture)  A set of protocols defined by Microsoft and others.  It provides an infrastructure that supports the most commonly requested demands for commercial Web service: security and routing. WS-Security  It allows authentication established by one system to be accepted by others (federated identity).

24 Web Service Terminology - others WS-Routing  The typical mode for WS-Routing is to create a one- way path that the SOAP message must take. WS-Referral  A protocol directly related to WS-Routing.  It allows for changes to the routing of a SOAP message to be made dynamically.

25 Delivering Web Service Service-oriented Architecture  Created by IBM.  Service provider A server or system makes a Web service available over network. Provides a service interface, that enables other applications to access the service.  Service broker Service provider publishes its service to service broker. Service broker communicates with requesters and directs them to the appropriate provider.

26 Delivering Web Service  Service requester A networked server or system that access or employed a Web service. Service provider Service broker Service requester bind publish find

27 Web Service Life-cycle Stages CreationDesign, development, documentation, testing and distribution. PublicationWeb service hosting and maintenance. PromotionDirectory services, value-added services and accreditation. SaleAuditing and accounts management.

28 ASP.Net Web Service Architecture Browser VB Application Office Documents Other Web Service Classic ASP.ASP ASP.Net.ASPX XML Web Services.ASMX Document-Style ListenerWSDL Wrapper Classes RPC-Style ListenerWSDL Business Objects Database Server SOAP Messages