Web to Database Connectivity Tools Frank Cervone Assistant Director for Systems DePaul University Libraries Access ‘98 October 3, 1998

Introduction Databases Database APIs Programming Languages Access Models

Databases Flat files Relational databases Object-oriented databases

Flat Files Simple implementation –regular text –basic encoding –word, excel files

dbm Files UNIX/gnu library of routines that manage data files containing key/data pairs read, write, delete by key nonsorted traversal of all keys

dbm File Example There is no inherent mechanism for ensuring data consistency

Relational Databases Most common data management scheme Data is organized into two-dimensional tables of rows and columns –Data is decomposed to its simplest form –Normalization reduces data inconsistency –Referential integrity

Relational Database Example Student Table Course Table Enrollment Table

Object-oriented Databases Can mean many things Data exists as objects –each object encapsulates data (attributes) methods (procedures) is a member and instance of a class of objects may be a subset of a class and inherit characteristics of the superclass

Object-oriented Example Students Courses

Database APIs Native-interface ODBC JDBC CORBA

Native Interface Low-level interface Direct call from a program to an access method to retrieve data Typically only used directly when accessing flat files Often used from compiled programming languages

ODBC Open Database Connectivity Standard method for applications to request database information from other applications (i.e., database servers) Common interface and language (SQL) to disparate database systems Examples: Oracle, MS-SQL Server, MS-Access, DB2

ODBC Example Application MS-Access Driver Driver Manager MS-Access Database Oracle Driver Oracle Database MS-SQL Driver MS-SQL Database

JDBC™ Java Database Connectivity Interface to ODBC for Java programs Standard method for Java programs to request database information from other applications (i.e., database servers) Common interface and language (SQL) to ODBC-compliant database servers

CORBA Common Object Request Broker Architecture Standard method for requesting objects from object-oriented database servers Adoption has been slow, but is growing

Programming Languages Java C and/or C++ PERL/CGI VBScript/ASP

CGI Common Gateway Interface A standard programming interface to web server applications These applications act as gateways between the web server and the database

CGI Overview Client Web Browser Web Server Program or Script Database

CGI Details Browser sends URL request with embedded CGI program name Web server set environment variables, executes program, and passes form data via STDIN Program examines environment variables, reads STDIN, performs requested functions, calls database Database receives request from program and retrieves data

CGI Details Continued Database returns data to calling program Program acts on returned data –HTML page, text page, redirect command –sends results to web server via STDOUT Web server creates HTTP-formatted result Browser displays web page

CGI Interaction Client Web Browser Web Server Program or Script Database HTTP CGI ODBC

Using Databases from the Web CGI program –C, C++ –PERL Intermediate program –mSQL/Lite Database with web support –FileMaker Pro Special web server –VBScript/IIS –ColdFusion

Displaying the Data CGI program - –generates the web page on the fly Database with web support –page is generated by database program Intermediate program/Special web server - –page is interpreted and a new one is generated in its place

Interpreted Page Example <% set conn=server.createobject(“adodb.connection”) conn.open “DSN=Students;uid=master;pwd=test” set result=conn.execute(“select * fromenrollment”) response.write “ ” for I=0 to howmanyfields response.write “ ” & result(i).name & “ ” next response.write “ ”.. (etc.)

Scenarios FileMaker Pro MS-IIS/VBScript mSQL/Lite ColdFusion/Oracle

Suggestions Understand your current needs Project for your future plans Keep server diversity to a minimum Hire/train appropriate personnel