Web Technology and DBMS s CB 29 CPSC 356

Web Technology and DBMS’s (CB 29) CPSC 356 Database Design Ellen Walker Hiram College (Includes figures from Database Systems by Connolly & Begg, © Addison Wesley 2005)

What is the Internet? • Interconnected Networks – Interoperable via standards (TCP, IP) • History – ARPANet (late 60’s, early 70’s) - military – NSF took over, provided funding (1986) – Commercial backbones (1996 - present)

Internet vs. Intranet • Internet – Global, open, public – Called “extranet” to distinguish from Intranet • Intranet – Private network for exclusive use of an organization – Behind a firewall • Typically, limited interaction

Internet Evolution of a Business (Cisco) • E-mail • Web site • E-Commerce – Customers can place and pay for orders via web • E-Business – Complete integration of Internet technology into business’s infrastructure • Ecosystem – Entire business process automated - customers, suppliers, alliance partners, corporate infrastructure merged into seamless system

Web vs. Internet • Internet provides infrastructure of information transmission across the network • Web contains interlinked information (web pages) – Servers: contain pages and transmit on request – Clients (browsers): request and display pages to users

Languages of the Web • HTTP - protocol for sending / receiving web pages. Includes GET vs. POST • HTML - basic markup language (represents complex pages as text). Includes mechanism (href) to reference other pages. • XML - extended markup language generalization of HTML to represent more complex document information • (etc) -- this is not a complete list!

Limitations of HTTP • Each transaction consists of a single request for data and a single response. – GET = request data – POST = response (or data from form) • Protocol is “stateless” - does not retain information beteween transactions – Workarounds: cookies or hidden text

Static vs. Dynamic Web Page • Static web page – Contents of page stored in a file, served as originally written • Dynamic web page – Generated as needed – Only instructions for generating the page are stored (e. g. php query/display based on argument)

Dynamic Web Pages • Input provided as parameters or from forms in the page • Data generated from queries • Pages written in a “scripting language” (PHP is one example)

Requirements for Web-DBMS Integration • • • Ability to maintain data security Not tied to a single DBMS Not tied to a single browser Availability of all features of DBMS Open-architecture approach, supporting multiple servers, standard interoperability languages (e. g. DCOM, CORBA, XML, SOAP)

Advantages of Web Approach • • Simplicity Platform independence Graphical User Interface Standardization Transparent network access Simplified deployment Global access

Disadvantages • • (lack of) Reliability (lack of) Security Cost (!) Heavy (unpredictable) loads HTML limitations Bandwidth & Performance limitations Immaturity of platform & tools

Tools to Integrate the Web • Scripting Languages – Client-side or Server-side • Common Gateway Interface (CGI) – Server-side • • Web server extensions Java, J 2 EE, SQLJ, etc. Microsoft. Net Oracle’s Internet platform

Scripting languages • Programs embedded in HTML files on server • Behavior of all clients changed by changing script on server • Scripts are generally interpreted, not compiled

Java. Script • Server-side or Client-side (client-side more common) • Allows immediate reaction to user interface widgets • Object-based (Document Object Model) • Limited relative to Java • (VBScript : Visual Basic = Java. Script : Java)

Perl, PHP • Server side languages • Heavy Unix flavor (e. g. use of regular expressions) • PHP preferred for Linux – Integrates with Apache HTTP Server – Works well with My. SQL or Postgre. SQL

Common Gateway Interface (CGI) • Defines how scripts communicate with web servers – Uses Environment variables, standard I/O on server side – Uses HTML Forms on client side (original impetus forms) • Nearly any programming language can run on server (std. output returned to browser) • Server runs script based on filename (x. cgi, x. php, etc) - this is configurable

CGI Environment

Advantages of CGI • • • Standardized interface Programming-language independent Web-server independence Simplicity Wide acceptance

Disadvantages of CGI • Web server can be bottleneck • Problems from HTTP Statelessness – No validation of user input (must go “back” to repopulate form) – No transactions (must connect to database on every page) • Security risks – Scripts with greater privileges than server – Risk of unanticipated (or malicious) user input

HTTP Cookies • Stored by browser in a file on client • Cookies set / retrieved by HTTP request • Issues: – Not supported by all browsers – For privacy reasons, users disable cookies

Non-CGI Gateways • API Extensions to server (NSAPI, ISAPI) • Scripts loaded as part of server – Direct interaction with back end – One copy per server, not per request – Changes server executable (risk? ) • Requires specialized programmers

Vendor Specific Scripting • Developed by vendors as server add-ons – JSP - Java Server pages (Sun) – ASP - Active Server pages (Microsoft) • Flexibility of CGI, without performance overhead and I/O limitations • Better integration with vendor’s other web solutions • Some compatibility limitations

Sun’s Java Platform • Java language: “write once run anywhere” • Assorted “editions” – ME (embedded) – SE (standard) - for desktop & workstation – EE (enterprise) - for multi-tier, robust, multiuser applications

Java 2 Platform (1999)

Microsoft. NET Platform • Integrated across servers, OS, applications, programming language environments • OLE - Object Linking and Embedding – Shared objects that provide specific functionality (e. g. sound clip) • [D]COM([Distributed] Component Object Model) – Connects client application and object (binarycompatible components)

MS OLE - DB

. NET Framework

Oracle’s Approach • Aimed at distributed environments • N-tier architecture, based on industry standards • Designed for e-business • Components include: – Top. Link (relate Java objects to relational databases) – Portal (entry point for web access) – Business Intelligence (Reports, Discoverer, etc)

Oracle Internet Platform