Web Technologies and Database Administration Systems

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Web Technologies and Database Administration
Systems
John Rowan
CS 8990, Summer 2004
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• The Internet Information Sharing
• The emergence of the web as a way of sharing
  information has made it one of the fastest
  growing technologies.
• Its platform-independence make it appealing for
  applications and sharing data.
• The Database Management System (DBMS) has become
  the backbone for servicing data dynamically.

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• 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

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• 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)

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• 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.

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• Web/DBMS Integration Considerations (cont)
• A connectivity solution that takes advantage of
  all the features of an organizations DBMS.
• An open-architecture approach to allow
  interoperability with a variety of systems and
  technologies for example, support for
• - different web servers
• Microsofts (Distributed) Common Object Model
  (DCOM/COM)
• CORBA/IIOP (Internet Inter-ORB protocol)
• Java/RMI (Remote Method Invocation).

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• 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.

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• 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.

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• Current Web Application Communication Standards
• Common Object Request Broker (CORBA)
• Distributed Component Object Model (DCOM)
• Simple Object Access Protocol (SOAP)
• Remote Method Invocation (RMI)

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• 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.

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• 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.

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• 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.

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• CORBA Illustration

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• 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.

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• 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.

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• RMI Illustration

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• 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.

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• 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.

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• SOAP Components

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• 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.
• Doesnt implement security because it is a wire
  protocol (relies on HTTP).

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• 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.

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• 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.

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• 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.

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• Advantages and Disadvantages
• of SOAP, CORBA, and RMI
• Disadvantages RMI
• Not full-featured middleware.
• No mechanism for object description.
• No language independence.

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• Other Web Technologies
• Java Servlets Java Server Pages
• Common Gateway Interface (CGI)
• Active Server Pages (ASP)
• Perl
• PHP
• JavaScript VBScript