CSM3115: Architectures for Enterprise Wide Computing: CSM3115: Architectures for Enterprise Wide Computing Developing Distributed and E-commerce Applications By D. Ince, Addison Wesley, 2002/2003


Chapter 1. An Introduction to distributed applications and ecommerce: Chapter 1. An Introduction to distributed applications and ecommerce Objectives: To detail what is meant by the term 'e-commerce'. To examine some typical e-commerce applications. To detail some of the problems that are encountered when developing e-commerce applications. To describe briefly some of the technologies that are used to support e-commerce applications. To show how some of the technologies detailed in the book are used in concert to realise a typical e-commerce system.


Distributed Systems & Java: Distributed Systems & Java A general introduction to applications distributed across a number of computers Java used for illustration Does not deal with under the bonnet issues Not a hacking course


The rationale for using Java: The rationale for using Java Portable Exhibits all the main features of object orientation Has hooks into the main distributed technologies Free and widely available


Some ecommerce applications: Some ecommerce applications Auction sites Affiliate sites Banner advertising Bulk buying sites Shopping malls Portals Digital publishing sites Licensing sites Name your price sites Last minute sites


Etailing (Book store): Etailing (Book store) Visitors: browse reviews, read feature articles, search for book details, order books and track progress of orders Functions: stock, payment and customer payment management; delivery; and market analysis


Distributed system functions: Distributed system functions Distributed functions Core functions are those which are found in any type of application, for example payment processing Distributed functions are those concerned with maintaining distributed system


Example (i) auction sites: Example (i) auction sites Auctions either held in real-time or in elapsed time Uses the Web Profit made from commissions and also from banner adverts


Example (ii) search engines: Example (ii) search engines Used to find information on the Web Many general purpose engines, for example Lycos, Yahoo Mainly use automatic indexing, some use human indexers Revenue from advertising


Change notification sites: Change notification sites The Web is incredibly dynamic: pages disappear or are updated very frequently Such sites inform webmasters when these events happen Revenues raised from charging for the service or banner adverts


Email providers: Email providers Provide Web-based email services Sometimes the service is tiered with the lower tier free Revenues from banner advertising. One of the most popular applications


The main facilities of the Internet: The main facilities of the Internet The World Wide Web FTP Email Mailing lists Newsgroups


The World Wide Web: The World Wide Web Browsers Browsers Browsers Web server


The Web: The Web Simple but large distributed system Servers provide Web files Browsers consume and display Web files Web documents expressed in HTML Two way communication, via forms Example of clients and servers


Issues in distributed application development (i): Issues in distributed application development (i) Legacy technology Space problems Stateless server dispensing static pages Security and privacy Programming and abstraction


Issues in distributed application development (ii): Issues in distributed application development (ii) Transactions Speed of development Standards Design


Legacy technology: Legacy technology The initial design of the Web was simple: static pages and no dynamic content Changed Addresses running out Changing Web protocol is stateless Changed


Security and privacy: Security and privacy Internet is an open system. Architecture and protocols are public Good effect is that errors can be spotted and rectified quickly Bad effect is that privacy can be compromised


How secure is the Internet?: How secure is the Internet? In 1996 Dan Farmer, one of the leading members of the Internet security community, analysed a number of Internet sites using a tool known as SATAN which reports on security vulnerabilities. He discovered that out of the 2200 sites he accessed, 1700 were relatively easy to attack (77 per cent of the sites). This is a staggering figure; however, what makes it more staggering is the fact that Farmer chose sites which should have been neurotic about security, for example sites owned by banks, government agencies, insurance companies and credit card companies.


Speed of development: Speed of development Faster development times needed for Internet applications Hence the need for OO languages A potential use for patterns More and more companies using rapid development methods Current estimates: one calendar year is equivalent to seven Web years


Problems with transactions: Problems with transactions A transaction is applied to stored data and can alter the data Concurrency problems Inconsistent update problems Data changed in the presence of failure


Distributed system design: Distributed system design Designing core functions is just as in conventional systems However there are design issues concerned with: Reliability Transmission media Speed


Design: Design Client Client Client Server Transmission media can be slow A server can malfunction Transmission media can fail


Design issues: Design issues Coping with server failure Coping with transmission media failure Coping with slow transmission speeds such as those found in the Internet Coping with synchronicity


The Sydney Olympic games system: The Sydney Olympic games system IBM was responsible for the computer systems which were used in the 2000 Sydney Olympic games. There were a number of components to the system, these included: A Web site which was publicly accessible and which contained features on the games, the competitors and the results. A games management system which administered the logistics of the games, for example arranging transportation, accreditation and accommodation for athletes. A games results system which captured input from all the events in the games and distributed them to judges, scoreboards, competitors, commentators and the Web site detailed in the first bullet point above. A commentator information system which provided real-time information to journalists and broadcasters, for example this system would flash up on a commentator's PC the times achieved by the runners in a race, only a few seconds after the race was completed.


The Sydney Olympic games system: The Sydney Olympic games system The statistics associated with the development were staggering: 7300 PCs were used as clients. 2000 information workstations and kiosks were spread around the Olympic site. 1500 IBM staff worked on the system. 10 km of cable was laid. 815 network switches were employed to transport and send data. 600 servers were used to store data and provide other services. 13 million lines of code were written. During the 16 days of the Olympics the Web site had 230 million page views, 8.7 million unique visitors and 11.3 billion hits. The highest number of hits in a day for the Web site was 874.5 million. 371 654 e-mail messages were sent to competitors from fans. The system achieved 100 per cent availability.