Slide 18.1 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. An Introduction to Object-Oriented Systems Analysis and Design with UML and the Unified Process McGraw-Hill, 2004 Stephen R. Schach

Slide 18.2 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. CHAPTER 18 WEB-BASED INFORMATION SYSTEMS

Slide 18.3 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Chapter Overview l Prelude to the Web l Security Issues l Analysis and Design Implications of Networks l Web-Based Information Systems

Slide 18.4 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Stage 1: The first electronic computers (1940s) –They were huge and and unbelievably expensive l They could be used by only one user at a time l They were operated in batch mode –There was no interaction between user and computer from program initiation until termination

Slide 18.5 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Deployment diagram of a first-generation computer

Slide 18.6 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Stage 2: Interactive timesharing (early 1960s) –The computer was connected via a wire to dumb terminals l Advantage: –Many users could use an expensive computer at the same time l Disadvantages: –Cost of the computer –Complex operating system

Slide 18.7 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Deployment diagram of a interactive timesharing computer

Slide 18.8 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Stage 3: The IBM personal computer or PC (1981) –Was used by one person at a time l It was –Small, and –Cheap

Slide 18.9 Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Deployment diagram of a personal computer

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Personal computers and first-generation computers –Supported only one user at a time, and –Were similar in computing power l The personal computer was over a thousand times –Cheaper, and –Lighter

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Stage 4: Networking –Connecting a set of personal computers together so that they can communicate with one another l One important configuration –Client–server network (1990s) –Personal computers (the clients), are connected to a central computer (the server), which has a large disk

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l Client–server network

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l A client–server network is identical to a timesharing compute except –Each dumb terminal is replaced by a personal computer

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l A client–server network can be used in two basic ways –As a timesharing computer –As a distributed computer

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l It can be hard for a client to communicate with the server –Middleware is needed to achieve interoperability »The mutual cooperation of compiled code »From different vendors, »Implemented in different languages, and »running on different platforms

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l A larger client–server network with different types of clients and servers

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l The World Wide Web

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l The Web is highly heterogeneous –Portability is therefore a nonnegotiable requirement of all Web-based information systems l This problem has been solved –There are strict standards regarding the format of files that are passed over the Web –Examples: »HTML (HyperText Markup Language) »XML (eXtensible Markup Language, an extension of HTML)

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Prelude to the Web (contd) l The World Wide Web can also be used in two basic ways: –As a page reader (browser) –As a distributed computer

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Security Issues l E-commerce systems encrypt (encode) credit card numbers –If an order goes astray there is no danger that a person who sees it can misuse the credit card number l However, encryption of credit card numbers may not be of critical importance –Very few messages go astray –An unintended recipient may be honest –There are better ways for crooks to acquire credit card numbers

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Security Issues (contd) l The real problem is –How credit card numbers are stored on the e-commerce company computer l Credit card numbers (and other sensitive data) should be stored in encrypted form –Because hackers can break into the data store after the numbers have been received l If they have to be stored in unencrypted form –They must be protected by passwords and other security mechanisms

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Analysis and Design Implications of Networks l An information system is to be implemented on a single computer: –The systems analysis and design is described in Chapters 1 through 17

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Analysis and Design Implications of Networks l The same information system is to be implemented on an interactive timesharing computer l How does the systems analysis and design change? –The requirements must now state that input and output will be performed on the user’s keyboard and screen –There are security and reliability implications, but mainly for the detailed design and implementation artifacts »They are not the concern of systems analysts l Systems analysis and design changes are minor

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Analysis and Design Implications of Networks l Similarly, from the viewpoint of systems analysis and design, there is not much difference between –A personal computer and the first-generation computer, or –A personal computer and a client–server network

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Analysis and Design Implications of Networks l Again, from the viewpoint of systems analysis and design, there is not much difference between a client–server network and the World Wide Web –There are networking issues »They are not the concern of systems analysts –The World Wide Web has portability and interoperability implications –Interoperability can cause really hard problems »They are not the concern of systems analysts

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Web-Based Information Systems l The Web is the ultimate client–server network l All possible network problems are present, including –Security, and –Interoperability

Slide Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved. Web-Based Information Systems (contd) l The issues arising from the development of Web- based information systems are extremely important –Some of them can be remarkably hard to solve l But none of them impact the task of the systems analyst