1. The Internet Database Environment Chapter 3 1

2. Outline Characteristics of Web-Based Database Applications Database-enabled intranet/internet environment Internet and Intranet Services Web-Related Terms Communications Technology Internet-Related Languages Server/Client Extensions Web Server Interfaces Dynamic Web development environment Web services deployment Web Security 2

3. Characteristics of Web-Based Database Applications Web browsers are simple to use Information transfer can take place across different platforms Development time and cost have been reduced Sites can be static (no database) or dynamic/interactive (with database) –Potential e-business advantages (improved customer service, faster market time, better supply chain management) 3

4. Database-enabled intranet/internet environment 4

5. Internet and Intranet Services Web server Database-enabled services Directory, security, authentication E-mail File Transfer Protocol (FTP) Firewalls and proxy servers News or discussion groups Document search Load balancing and caching 5

6. File Transfer Protocol (FTP) The most common protocol for transferring files between two locations The protocol supports the following: – User id based login (User-id/Password combination) – Hierarchical folders – File Management (Rename, Delete, Upload, Download, Download with overwrite, Download with append) 6

7. Proxy Server a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers. Proxies were invented to add structure and encapsulation to distributed systems. Today, most proxies are web proxies, facilitating access to content on the World Wide Web and providing anonymity. 7

8. Firewalls A firewall is a software or hardware-based network security system that controls the incoming and outgoing network traffic based on applied rule set. It establishes a barrier between a trusted, secure internal network and another network (e.g., the Internet) that is not assumed to be secure and trusted. 8

9. Web Load Balancer Load Balancers provide increased performance to your website by distributing traffic efficiently to multiple servers, and create a more robust and fault- tolerant system. 9

10. Load Caching A temporary storage area where frequently accessed data can be stored for rapid access. Cached data are stored in the memory. Defining frequently accessed data is a matter of judgment and engineering. −What resource should be stored in the cache? −How long should the resource be stored in the cache? 10

11. Web-Related Terms World Wide Web (WWW) –The total set of interlinked hypertext documents residing on Web servers worldwide. Browser –Software that displays HTML documents and allows users to access files and software related to HTML documents. Web Server –Software that responds to requests from browsers and transmits HTML documents to browsers. Web pages–HTML documents –Static Web pages–content established at development time. –Dynamic Web pages–content dynamically generated, usually by obtaining data from database. 11

12. Communications Technology IP Address –Four numbers that identify a node on the Internet –e.g. 131.247.152.18 Hypertext Transfer Protocol (HTTP) –Communication protocol used to transfer pages from Web server to browser –HTTPS is a more secure version Uniform Resource Locator (URL) –Mnemonic Web address corresponding with IP address –Also includes folder location and html file name Typical URL 12

13. Internet-Related Languages (1) Hypertext Markup Language (HTML) –Markup language specifically for Web pages Standard Generalized Markup Language (SGML) –Markup language standard Extensible Markup Language (XML) –Markup language allowing customized tags XHTML –XML-compliant extension of HTML 13

14. Internet-Related Languages (2) Java –Object-oriented programming language for applets JavaScript/VBScript – Scripting languages that enable interactivity in HTML documents Cascading Style Sheets (CSS) –Control appearance of Web elements in an HML document XSL and XSLT –XML style sheet and transformation to HTML 14

15. Server-Side Extensions Programs that interact directly with Web servers to handle requests −e.g. database-request handling middleware Web-to-database middleware 15

16. Web Server Interfaces Common Gateway Interface (CGI) –Specify transfer of information between Web server and CGI program –Performance not very good –Security risks Application Program Interface (API) –More efficient than CGI –Shared as dynamic link libraries (DLLs) Java Servlets –Like applets, but stored at server –Cross-platform compatible –More efficient than CGI 16

17. Web Servers Provide HTTP service Passing plain text via TCP connection Serve many clients at once –Multithreading –Multiprocessing Load balancing approaches: –Domain Name Server (DNS) balancing One DNS = multiple IP addresses –Software/hardware balancing Request at one IP address is distributed to multiple servers –Reverse proxy Intercept client request and cache response 17

18. Client-Side Extensions Add functionality to the browser Plug-ins –Hardware/software modules that extend browser capabilities by adding features (e.g. encryption, animation, wireless access) ActiveX –Microsoft COM/OLE components that allow data manipulation inside the browser Cookies –Block of data stored at client by Web server for later use 18

19. Components for Dynamic Web Sites DBMS–Oracle, Microsoft SQL Server, Informix, Sybase, DB2, Microsoft Access, MySQL Web server–Apache, Microsoft IIS Programming languages/development technologies – ASP.NET, PHP, ColdFusion, Coral Web Builder, Macromedia’s Dreamweaver Web browser–Microsoft Internet Explorer, Netscape Navigator, Mozilla Firefox, Apple’s Safari, Opera Text editor–Notepad, BBEdit, vi, or an IDE FTP capabilities–SmartFTP, WS_FTP 19

20. Dynamic Web development environment 20

21. Web Services XML-based standards that define protocols for automatic communication between applications over the Web. Components of Web Service: –Universal Description, Discovery, and Integration (UDDI) Technical specification for distributed registries of Web services and businesses open to communication on these services –Web Services Description Language (WSDL) XML-based grammar for describing Web services and providing public interfaces for these services –Simple Object Access Protocol (SOAP) XML-based communication protocol for sending messages between applications via the Internet Challenges for Web Services –Lack of mature standards –Lack of security 21

22. Web services protocol stack 22

23. Deployment of Web services 23

24. Website Security Firewall – hardware/software security component that limits external access to company’s data. Proxy server – firewall component that manages Internet traffic to and from a LAN. Router – intermediate device that transmits message packets to correct destination over most efficient pathway. Intrusion detection system (IDS) – system that identifies attempt to hack or break into a system. 24

25. Establishing Internet security Firewall to limit external access to data Routers to transmit message packets to correct destination IDS to monitor and recognize security breach attempts 25