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Lecture plan

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Non-CGI gateways , e.g. Application Programming Interfaces (APIs), can be used ... Analagous to CGI programming, but faster, portable, more extensible, and more secure ... – PowerPoint PPT presentation

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Title: Lecture plan


1
Lecture plan
  • Information retrieval (from week 11)
  • Databases and the Web

2
Web/DBMS architecture
  • 3-layer architecture
  • User interface layer (client)
  • E.g. a Web browser
  • Business logic and data processing layer
    (application server)
  • E.g. a Web server
  • DBMS (database server)

3
Web/DBMS integration
  • Scripting languages
  • Common Gateway Interface (CGI)
  • Web server extensions, e.g. API
  • Java resources, e.g. JDBC, Servlets, JavaServer
    Pages (JSPs)
  • HTTP cookies
  • XML

4
Scripting languages
  • Script code is embedded in HTML, so is downloaded
    each time the page is accessed
  • Programs can be written with standard programming
    logic
  • E.g. JavaScript includes Java-based functions and
    scripts to respond to user input, page
    navigation, etc
  • E.g. Perl combines features of C with some Unix
    utilities to create and manipulate files, network
    sockets, database connectivity, etc

5
Common Gateway Interface (CGI)
  • A specification for transferring information
    between Web servers and CGI programs using CGI
    scripts
  • CGI scripts can be written in any language that
    supports the reading and writing of an operating
    systems environment variables, e.g. Perl, Java,
    C
  • Advantages are simplicity, language independence,
    Web server independence, wide usage
  • Disadvantage is that a new process is started up
    each time a CGI script is invoked, which can be
    costly for the Web server

6
Web server extensions
  • An alternative to CGI
  • Non-CGI gateways , e.g. Application Programming
    Interfaces (APIs), can be used to add
    functionality to the Web server
  • API provides a method for creating an interface
    between the Web server and back-end applications
    using dynamic linking or shared objects
  • Advantages are improved functionality and
    performance
  • Disadvantage is reliance on expert programming

7
Java resources 1
  • Java offers a large set of resources to support
    Web/DBMS integration
  • JDBC
  • Defines a database access API that supports basic
    SQL functionality
  • Java can be used as the host language for writing
    DB applications
  • Higher-level APIs can be built on top, e.g. the
    JDBC-ODBC bridge which provides JDBC access using
    ODBC drivers
  • ODBC (Open DataBase Connectivity standard)
    provides a common interface for accessing
    heterogeneous SQL DBs
  • A single application can thus access different
    SQL DBMSs through a common set of code IF the
    DBMSs are ODBC-compliant

8
Java resources 2
  • Java Servlets
  • Programs that run on a Java-enabled Web server
    and build Web pages
  • Analagous to CGI programming, but faster,
    portable, more extensible, and more secure
  • Java Server Pages (JSPs)
  • A Java-based server-side scripting language that
    allows static HTML to be mixed with
    dynamically-generated HTML
  • Works with most Web servers, including Apache
    HTTP Server

9
HTTP cookies
  • A piece of information stored on the client on
    behalf of the server
  • Sent back to the server with each new client
    request
  • Can be used to store registration information or
    preferences

10
XML
  • Meta-language that enables designers to create
    their own customised tags to provide
    functionality not available with HTML
  • A restricted version of SGML (Standardised
    Generalised Markup Language), which itself is too
    complex for general use
  • Advantages are simplicity, platform-independence
    / vendor-independence and extensibility
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