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Software Architecture in Practice

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CGI scripts allowed dynamic request information to be returned to clients ... Proxy Servers claim for PERFORMANCE. Reuters and Firewalls claim for SECURITY ... – PowerPoint PPT presentation

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Title: Software Architecture in Practice


1
Software Architecturein Practice
  • RiSEs Seminars
  • Basss at all Book Chapters 13
  • Fred Durão

2
Summary
  • The world wide web A case study in
    Interoperability (Chapter 13)
  • The original requirements
  • Architectural Solution
  • The evolution of web based e-commerce
    architecture
  • The architectural business cycle today

3
The word wide web A case study in
Interoperability
4
History
The World Wide Web Chapter 13
  • Tim Berners Lee and CERN members seen the need of
    creating a information network
  • In 1989, Tim Berners Lee created a document named
    Information Management A proposal
  • In 1990, a reformulated version of his document
    became a project named World Wide Web

5
The www original requirements
The World Wide Web Chapter 13
  • Remote access across networks
  • Heterogeneity
  • Noncentralization
  • Access to existing data
  • Ability for users to add data
  • Private links
  • Bells and whistles the data display was on 24 x
    80 character ASCII Terminal
  • Data analysis
  • Live links given that information changes all
    the time
  • Some non requirements became requirements like
    SSL (Secure Socket Layer) and HTTPS (HttpSecure)

6
Internet Statistics
The World Wide Web Chapter 13
Source Used with permission of Matthew Gray of
the Massachusetts Institute of Technology
7
Internet Growth
The World Wide Web Chapter 13
  • Web has been doubling in size every 3 to 6 year
    months
  • From 130 sites in 6/1993 to more that 230.000
    sites in mid-1996
  • and 27 million in early 2001
  • Internet Backbones in the USA 1996

8
Architectural Solution
The World Wide Web Chapter 13
  • Based on client and servers and wwwLibs
  • - compact, portable library that can be built on
    to create Web-based applications such as clients,
    servers, databases, and Web Spiders

9
libWWW layers
The World Wide Web Chapter 13
Support a set of application functionalities for
writing applications
Support a set of network-protocol-aware modules,
like HTTP, FTP, TELNET
Provides the abstraction of stream of all data
transported
Provides standard interfaces to Web Applications
Portability layer that provide platform-independen
t function
10
Lessons learned from libWWW
The World Wide Web Chapter 13
  • Formalized application programming interfaces
    (APIs) are required
  • Functionality and the APIs that present it must
    be layered
  • The library must support a dynamic, open-ended
    set of features
  • Processes built on the software must be thread
    safe

11
An Early Client-Server Architecture using libWWW
The World Wide Web Chapter 13
  • WWW Client
  • External Viewer
  • HTTP Client
  • UI Manager, Cache Manager and more
  • WWW Server
  • CGI
  • HTTP Server
  • Stream Manager, Access Control and more

12
Common Gateway Interface - CGI
The World Wide Web Chapter 13
  • CGI is one of the most important requirement
    driving the evolution of Web software
  • CGI scripts allowed dynamic request information
    to be returned to clients
  • The most common use of CGI were create dynamic
    HTML document and return it to users
  • CGI allowed users put information into the web,
    in contrast to get operation that servers
    normally provide. E.g. add info on databases by
    filling out a form

13
How the WW Achieved Quality Goals
The World Wide Web Chapter 13
14
The Evolution of Web-Based E-Commerce
Architectures
The World Wide Web Chapter 13
  • The new requirements
  • High performance
  • Customer will not tolerate the site simply
    refusing
  • their requests
  • High availability
  • The Web Sites have to be available 24/7
  • Scalability
  • Possibility of growth to maintain acceptable
    levels of customer service.
  • Security
  • Adapt mechanisms for avoiding stealing or
    modifying data.
  • Modifiability
  • Ability for changes

Customer
15
A typical e-commerce system
The World Wide Web Chapter 13
16
E-Commerce Architecture achieving qualities
The World Wide Web Chapter 13
  • Web Browsers claim for MODIFIBILITY
  • HTTPS claims for SECURITY
  • Proxy Servers claim for PERFORMANCE
  • Reuters and Firewalls claim for SECURITY
  • Load Balancing claims for SCALABILITY and
    AVAILABILTY

17
E-Commerce Architecture achieving qualities
The World Wide Web Chapter 13
  • Web Servers claim for PERFORMANCE
  • Databases claim for PERFORMANCE, SCALABILITY and
    AVAILABILITY
  • Application Servers claim for PERFORMANCE,
    MODIFIABILITY and SCALABILITY

18
The Architecture Business Cycle Today
The World Wide Web Chapter 13
  • Several types of organization provide the
    technical environment Service providers and Data
    providers
  • A number of open-source projects have increased
  • E.g. Apache Project
  • Web-enable languages, particularly Java, are
    changing the way functionality is developed over
    the Web
  • The emergence of the Web as a distributed
    development environment has given rise to several
    new organizations and products

19
References
The World Wide Web Chapter 13
  • Bass L., Clements P. and Kazman R. Software
    Architecture in Practice. Second Edition, 2003.
  • o mundo pode esperar
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