Evolution of Distributed Component Systems

1
Chapter 1

• Evolution of Distributed Component Systems

2
Objectives

• Describe the architectures in software
  development
• Two-tier client server architecture
• Three-tier architecture
• Traditional n-tier approach
• Distributed component system and layered
  architecture
• Discuss the advantages and disadvantages
  associated with the above approaches

3
Monolithic Applications
4
Monolithic Applications (1)

• Drawbacks
• Incorporating changes is a tedious job
• No data sharing possible

5
Modern Applications

• The Features
• Performance
• Scalability
• Extensibility
• Availability
• Reliability
• Maintainability
• Security

6
Various Architectures

• Two-tier client server architecture
• Three-tier architecture
• N-tier architecture
• Distributed component approach and layered
  architecture

7
Two-tier Architecture
8
Two-tier Architecture (1)

• Advantages
• Rules for data integrity implemented on the
  server
• Implementation of powerful hardware for the
  server enhances the availability and reliability
  of the application

9
Two-tier Architecture (2)

• Drawbacks
• Business logic present on every client
• Increase in the number of clients requests
  results in slower responses
• Difficult to make changes to the business logic

10
Three-tier Architecture
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Three-tier Architecture (1)

• Advantages
• The business logic shared among various clients
• The business logic, or the database type or
  schema changed without impacting the clients
• The middle tier hidden behind the firewall
• Increased availability of system resources
• Selective upgrading of parts of the architecture

12
Three-tier Architecture (2)

• Drawbacks
• The application tier not standardized
• The desired scalability level not available

13
N-tier Architecture
14
N-tier Architecture (1)

• Advantages
• In addition to the advantages of three-tier,
  n-tier has
• The desired scalability level
• Increased system resources

15
N-tier Architecture (2)

• Drawbacks
• Different application objects to cater to
  different user needs
• Objects not able to communicate with each other

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Distributed Component Architecture
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Distributed Component Architecture (1)

• Characteristics
• Components communicate with each other using
  interfaces
• Components maintain identity
• Components maintain the state on the server
• Easy modification of the business logic without
  affecting any other logic

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Distributed Component Architecture (2) (Contd. .)

• Components leverage their context object for
  services such as security, persistence, and
  transactions
• Components require Application Server to run
• Components used as plug and play devices

19
Layered Architecture

• Ways for achieving system flexibility
• Encapsulation
• Separation of Concerns (Abstraction)