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Lecture plan Information retrieval (from week 11)

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Presentation on theme: "Lecture plan Information retrieval (from week 11)"— Presentation transcript:

1 Lecture plan Information retrieval (from week 11)
Databases and the Web Jane Reid, BSc/IT DB, QMUL, 25/3/02

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) Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 system’s 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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

8 Java resources [2] Java Servlets Java Server Pages (JSPs)
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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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 Jane Reid, BSc/IT DB, QMUL, 25/3/02

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