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    JohnRowan.ppt JohnRowan.ppt Presentation Transcript

    • Web Technologies and Database Administration Systems John Rowan CS 8990, Summer 2004
      • The Internet & Information Sharing
      • The emergence of the web as a way of sharing information has made it one of the fastest growing technologies.
      • It’s platform-independence make it appealing for applications and sharing data.
      • The Database Management System (DBMS) has become the backbone for servicing data dynamically.
      • The Internet: Brief History
      • Started in the late 60s early 70s as a project called Advanced Research Projects Agency Networks (ARPANET).
      • - U.S. Department of Defense
      • Uses suite of package switching called TCP/IP or Transmission Control Protocol and Internet Protocol in 1983
      • The Internet: Brief History (cont)
      • Has grown to support over 650 million users in over 100 countries.
      • It is regulated bye the Internet Engineering Task Force or IETF.
      • - Responsible for promoting standards
      • - Harald T. Alvestrand is chairman
      • Supports numerous protocols (TCP, FTP, SSH, PPP)
      • Web/DBMS Integration Considerations
      • The ability to access valuable customer data in a secure manner.
      • Data and vendor independent connectivity to allow freedom of choice in the selection of the DBMS now and in the future.
      • The ability to interface to the database independent of any proprietary web browser or web server.
      • Web/DBMS Integration Considerations (cont)
      • A connectivity solution that takes advantage of all the features of an organization’s DBMS.
      • An open-architecture approach to allow interoperability with a variety of systems and technologies; for example, support for
        • - different web servers;
        • Microsoft’s (Distributed) Common Object Model (DCOM/COM)
        • CORBA/IIOP (Internet Inter-ORB protocol)
        • Java/RMI (Remote Method Invocation).
      • Web/DBMS Integration Considerations (cont)
      • A cost-effective solution that allows for scalability, growth, and changes in strategic directions, and helps reduce the costs of developing and maintaining applications.
      • Support for transactions that span multiple HTTP requests.
      • Support for session and applications based authentication.
      • Web/DBMS Integration Considerations (cont)
      • Acceptable performance.
      • Minimal administration overhead.
      • A set of high-level productivity tools to allow applications to be developed, maintained, and deployed with relative ease and speed.
      • Distributed applications
      • The integration of legacy applications into new systems.
      • The use of different programming languages to write new components.
      • Current Web Application Communication Standards
      • Common Object Request Broker (CORBA)
      • Distributed Component Object Model (DCOM)
      • Simple Object Access Protocol (SOAP)
      • Remote Method Invocation (RMI)
      • CORBA
      • A CORBA component is an object.
      • A CORBA class implements one or more CORBA interfaces
      • The execution locations is transparent to the client.
      • The server process advertises one or more named objects. The client process has no named objects.
      • CORBA (cont)
      • Client access remote objects by the way of references that have the same interface as remote objects. They forward all method invocations to the server for remote object execution.
      • The CORBA ORB runs within every CORBA process for communicating with other ORBS.
      • The CORBA ORB acts like a message bus between objects.
      • CORBA (cont)
      • The ORBs are able to communicate with each other by the use of a protocol known as the General Inter-Orb Protocol.
      • CORBA uses an Interface Definition Language (IDL) which enables the development of language-neutral interfaces that CORBA objects implements.
      • Language-specific compilers translate IDL into language-specific codes that are used to implement those interfaces.
      • CORBA Illustration
      • Remote Method Invocation (RMI)
      • It is used to access remote objects.
      • Java to Java only.
      • Uses the client-server protocol.
      • It is transparent and lightweight.
      • RMI (cont)
      • Remote References, Stubs, Skeletons
      • Remote references invoked on client exactly like local object references.
      • Remote interfaces declare exposed methods.
      • Methods are implemented on the client.
      • Stubs are used on the client and pretends to be a remote object.
      • Skeleton lives on the server and it receives requests from the stub. The skeleton communicates with the remote object and delivers response to the server.
      • RMI Illustration
      • Simple Object Access Protocol
      • Lightweight-protocol used for exchange of messages in a decentralized, distributed environment.
      • Used for Remote Procedure Calls (RPC)
      • W3C defines the use of SOAP with XML as payload and HTTP as transport.
      • SOAP Components
      • Envelope – Top element of the XML document representing the message.
      • Header – Optional layer that determines how a recipient of a SOAP message should process the message. Adds features to the SOAP message such as authentication, transaction management, message routing … etc.
      • Body – Used for RPC calls and error reporting.
      • Soap Fault – Used to carry error or status information within the SOAP Message.
      • SOAP Components
      • Advantages and Disadvantages
      • of SOAP, CORBA, and RMI
      • Advantages - SOAP
      • SOAP uses a widely known protocol for transport (HTTP). It is proven to be scalable.
      • It has a wide remote system interoperability.
      • Flexible for growth due to XML use.
      • Disadvantages – SOAP
      • Parsing of SOAP packet and mapping to objects reduces performance.
      • Doesn’t implement security because it is a wire protocol (relies on HTTP).
      • Advantages and Disadvantages
      • of SOAP, CORBA, and RMI
      • Advantages – CORBA
      • Multi-language support.
      • Can start up more then one service for load balancing.
      • Different ORBs can communicate.
      • Easy to extend new languages.
      • Open standard developed by international consortium.
      • Advantages and Disadvantages
      • of SOAP, CORBA, and RMI
      • Disadvantages – CORBA
      • Performance can be slow.
      • Implementations are still continually evolving.
      • Many ORBs do not provide full functionality of CORBA specifications.
      • Limited mainstream acceptance.
      • Advantages and Disadvantages
      • of SOAP, CORBA, and RMI
      • Advantages – RMI
      • Simple implementation.
      • No IDL.
      • Can pass and return existing Java objects.
      • Comes with JDK – No ORBs to buy.
      • Java is free.
      • Advantages and Disadvantages
      • of SOAP, CORBA, and RMI
      • Disadvantages – RMI
      • Not full-featured middleware.
      • No mechanism for object description.
      • No language independence.
      • Other Web Technologies
      • Java Servlets & Java Server Pages
      • Common Gateway Interface (CGI)
      • Active Server Pages (ASP)
      • Perl
      • PHP
      • JavaScript & VBScript